Provided by: parallel_20240222+ds-2_all bug

NAME

       parallel - build and execute shell command lines from standard input in parallel

SYNOPSIS

       parallel [options] [command [arguments]] < list_of_arguments

       parallel [options] [command [arguments]] ( ::: arguments | :::+ arguments | ::::
       argfile(s) | ::::+ argfile(s) ) ...

       parallel --semaphore [options] command

       #!/usr/bin/parallel --shebang [options] [command [arguments]]

       #!/usr/bin/parallel --shebang-wrap [options] [command [arguments]]

DESCRIPTION

       STOP!

       Read the Reader's guide below if you are new to GNU parallel.

       GNU parallel is a shell tool for executing jobs in parallel using one or more computers. A
       job can be a single command or a small script that has to be run for each of the lines in
       the input. The typical input is a list of files, a list of hosts, a list of users, a list
       of URLs, or a list of tables. A job can also be a command that reads from a pipe. GNU
       parallel can then split the input into blocks and pipe a block into each command in
       parallel.

       If you use xargs and tee today you will find GNU parallel very easy to use as GNU parallel
       is written to have the same options as xargs. If you write loops in shell, you will find
       GNU parallel may be able to replace most of the loops and make them run faster by running
       several jobs in parallel.

       GNU parallel makes sure output from the commands is the same output as you would get had
       you run the commands sequentially. This makes it possible to use output from GNU parallel
       as input for other programs.

       For each line of input GNU parallel will execute command with the line as arguments. If no
       command is given, the line of input is executed. Several lines will be run in parallel.
       GNU parallel can often be used as a substitute for xargs or cat | bash.

   Reader's guide
       GNU parallel includes the 4 types of documentation: Tutorial, how-to, reference and
       explanation/design.

       Tutorial

       If you prefer reading a book buy GNU Parallel 2018 at
       https://www.lulu.com/shop/ole-tange/gnu-parallel-2018/paperback/product-23558902.html or
       download it at: https://doi.org/10.5281/zenodo.1146014 Read at least chapter 1+2. It
       should take you less than 20 minutes.

       Otherwise start by watching the intro videos for a quick introduction:
       https://youtube.com/playlist?list=PL284C9FF2488BC6D1

       If you want to dive deeper: spend a couple of hours walking through the tutorial (man
       parallel_tutorial). Your command line will love you for it.

       How-to

       You can find a lot of examples of use in man parallel_examples. They will give you an idea
       of what GNU parallel is capable of, and you may find a solution you can simply adapt to
       your situation.

       If the example do not cover your exact needs, the options map
       (https://www.gnu.org/software/parallel/parallel_options_map.pdf) can help you identify
       options that are related, so you can look these up in the man page.

       Reference

       If you need a one page printable cheat sheet you can find it on:
       https://www.gnu.org/software/parallel/parallel_cheat.pdf

       The man page is the reference for all options, and reading the man page from cover to
       cover is probably not what you need.

       Design discussion

       If you want to know the design decisions behind GNU parallel, try: man parallel_design.
       This is also a good intro if you intend to change GNU parallel.

OPTIONS

       command
           Command to execute.

           If command or the following arguments contain replacement strings (such as {}) every
           instance will be substituted with the input.

           If command is given, GNU parallel solve the same tasks as xargs. If command is not
           given GNU parallel will behave similar to cat | sh.

           The command must be an executable, a script, a composed command, an alias, or a
           function.

           Bash functions: export -f the function first or use env_parallel.

           Bash, Csh, or Tcsh aliases: Use env_parallel.

           Zsh, Fish, Ksh, and Pdksh functions and aliases: Use env_parallel.

       {}  Input line.

           This replacement string will be replaced by a full line read from the input source.
           The input source is normally stdin (standard input), but can also be given with
           --arg-file, :::, or ::::.

           The replacement string {} can be changed with -I.

           If the command line contains no replacement strings then {} will be appended to the
           command line.

           Replacement strings are normally quoted, so special characters are not parsed by the
           shell. The exception is if the command starts with a replacement string; then the
           string is not quoted.

           See also: --plus {.} {/} {//} {/.} {#} {%} {n} {=perl expression=}

       {.} Input line without extension.

           This replacement string will be replaced by the input with the extension removed. If
           the input line contains . after the last /, the last . until the end of the string
           will be removed and {.} will be replaced with the remaining. E.g. foo.jpg becomes foo,
           subdir/foo.jpg becomes subdir/foo, sub.dir/foo.jpg becomes sub.dir/foo, sub.dir/bar
           remains sub.dir/bar. If the input line does not contain . it will remain unchanged.

           The replacement string {.} can be changed with --extensionreplace

           See also: {} --extensionreplace

       {/} Basename of input line.

           This replacement string will be replaced by the input with the directory part removed.

           See also: {} --basenamereplace

       {//}
           Dirname of input line.

           This replacement string will be replaced by the dir of the input line. See dirname(1).

           See also: {} --dirnamereplace

       {/.}
           Basename of input line without extension.

           This replacement string will be replaced by the input with the directory and extension
           part removed.  {/.} is a combination of {/} and {.}.

           See also: {} --basenameextensionreplace

       {#} Sequence number of the job to run.

           This replacement string will be replaced by the sequence number of the job being run.
           It contains the same number as $PARALLEL_SEQ.

           See also: {} --seqreplace

       {%} Job slot number.

           This replacement string will be replaced by the job's slot number between 1 and number
           of jobs to run in parallel. There will never be 2 jobs running at the same time with
           the same job slot number.

           If the job needs to be retried (e.g using --retries or --retry-failed) the job slot is
           not automatically updated. You should then instead use $PARALLEL_JOBSLOT:

             $ do_test() {
                 id="$3 {%}=$1 PARALLEL_JOBSLOT=$2"
                 echo run "$id";
                 sleep 1
                 # fail if {%} is odd
                 return `echo $1%2 | bc`
               }
             $ export -f do_test
             $ parallel -j3 --jl mylog do_test {%} \$PARALLEL_JOBSLOT {} ::: A B C D
             run A {%}=1 PARALLEL_JOBSLOT=1
             run B {%}=2 PARALLEL_JOBSLOT=2
             run C {%}=3 PARALLEL_JOBSLOT=3
             run D {%}=1 PARALLEL_JOBSLOT=1
             $ parallel --retry-failed -j3 --jl mylog do_test {%} \$PARALLEL_JOBSLOT {} ::: A B C D
             run A {%}=1 PARALLEL_JOBSLOT=1
             run C {%}=3 PARALLEL_JOBSLOT=2
             run D {%}=1 PARALLEL_JOBSLOT=3

           Notice how {%} and $PARALLEL_JOBSLOT differ in the retry run of C and D.

           See also: {} --jobs --slotreplace

       {n} Argument from input source n or the n'th argument.

           This positional replacement string will be replaced by the input from input source n
           (when used with --arg-file or ::::) or with the n'th argument (when used with -N). If
           n is negative it refers to the n'th last argument.

           See also: {} {n.} {n/} {n//} {n/.}

       {n.}
           Argument from input source n or the n'th argument without extension.

           {n.} is a combination of {n} and {.}.

           This positional replacement string will be replaced by the input from input source n
           (when used with --arg-file or ::::) or with the n'th argument (when used with -N). The
           input will have the extension removed.

           See also: {n} {.}

       {n/}
           Basename of argument from input source n or the n'th argument.

           {n/} is a combination of {n} and {/}.

           This positional replacement string will be replaced by the input from input source n
           (when used with --arg-file or ::::) or with the n'th argument (when used with -N). The
           input will have the directory (if any) removed.

           See also: {n} {/}

       {n//}
           Dirname of argument from input source n or the n'th argument.

           {n//} is a combination of {n} and {//}.

           This positional replacement string will be replaced by the dir of the input from input
           source n (when used with --arg-file or ::::) or with the n'th argument (when used with
           -N). See dirname(1).

           See also: {n} {//}

       {n/.}
           Basename of argument from input source n or the n'th argument without extension.

           {n/.} is a combination of {n}, {/}, and {.}.

           This positional replacement string will be replaced by the input from input source n
           (when used with --arg-file or ::::) or with the n'th argument (when used with -N). The
           input will have the directory (if any) and extension removed.

           See also: {n} {/.}

       {=perl expression=}
           Replace with calculated perl expression.

           $_ will contain the same as {}. After evaluating perl expression $_ will be used as
           the value. It is recommended to only change $_ but you have full access to all of GNU
           parallel's internal functions and data structures.

           The expression must give the same result if evaluated twice - otherwise the behaviour
           is undefined. E.g. in some versions of GNU parallel this will not work as expected:

               parallel echo '{= $_= ++$wrong_counter =}' ::: a b c

           A few convenience functions and data structures have been made:

            Q(string)
             Shell quote a string. Example:

               parallel echo {} is quoted as '{= $_=Q($_) =}' ::: \$PWD

            pQ(string)
             Perl quote a string. Example:

               parallel echo {} is quoted as '{= $_=pQ($_) =}' ::: \$PWD

            uq() (or uq)
             Do not quote current replacement string. Example:

               parallel echo {} has the value '{= uq =}' ::: \$PWD

            hash(val)
             Compute B::hash(val). Example:

               parallel echo Hash of {} is '{= $_=hash($_) =}' ::: a b c

            total_jobs()
             Number of jobs in total. Example:

               parallel echo Number of jobs: '{= $_=total_jobs() =}' ::: a b c

            slot()
             Slot number of job. Example:

               parallel echo Job slot of {} is '{= $_=slot() =}' ::: a b c

            seq()
             Sequence number of job. Example:

               parallel echo Seq number of {} is '{= $_=seq() =}' ::: a b c

            @arg
             The arguments counting from 1 ($arg[1] = {1} = first argument). Example:

               parallel echo {1}+{2}='{=1 $_=$arg[1]+$arg[2] =}' \
                 ::: 1 2 3 ::: 2 3 4

             ('{=1' forces this to be a positional replacement string, and therefore will not
             repeat the value for each arg.)

            skip()
             Skip this job (see also --filter). Example:

               parallel echo '{= $arg[1] >= $arg[2] and skip =}' \
                 ::: 1 2 3 ::: 2 3 4

            yyyy_mm_dd_hh_mm_ss(sec)
            yyyy_mm_dd_hh_mm(sec)
            yyyy_mm_dd(sec)
            hh_mm_ss(sec)
            hh_mm(sec)
            yyyymmddhhmmss(sec)
            yyyymmddhhmm(sec)
            yyyymmdd(sec)
            hhmmss(sec)
            hhmm(sec)
             Time functions. sec is number of seconds since epoch. If left out it will use
             current local time. Example:

               parallel echo 'Now: {= $_=yyyy_mm_dd_hh_mm_ss() =}' ::: Dummy
               parallel echo 'The end: {= $_=yyyy_mm_dd_hh_mm_ss($_) =}' \
                 ::: 2147483648

           Example:

             seq 10 | parallel echo {} + 1 is {= '$_++' =}
             parallel csh -c {= '$_="mkdir ".Q($_)' =} ::: '12" dir'
             seq 50 | parallel echo job {#} of {= '$_=total_jobs()' =}

           See also: --rpl --parens {} {=n perl expression=} --filter

       {=n perl expression=}
           Positional equivalent to {=perl expression=}.

           To understand positional replacement strings see {n}.

           See also: {=perl expression=} {n}

       ::: arguments
           Use arguments on the command line as input source.

           Unlike other options for GNU parallel ::: is placed after the command and before the
           arguments.

           The following are equivalent:

             (echo file1; echo file2) | parallel gzip
             parallel gzip ::: file1 file2
             parallel gzip {} ::: file1 file2
             parallel --arg-sep ,, gzip {} ,, file1 file2
             parallel --arg-sep ,, gzip ,, file1 file2
             parallel ::: "gzip file1" "gzip file2"

           To avoid treating ::: as special use --arg-sep to set the argument separator to
           something else.

           If multiple ::: are given, each group will be treated as an input source, and all
           combinations of input sources will be generated. E.g. ::: 1 2 ::: a b c will result in
           the combinations (1,a) (1,b) (1,c) (2,a) (2,b) (2,c). This is useful for replacing
           nested for-loops.

           :::, ::::, and --arg-file can be mixed. So these are equivalent:

             parallel echo {1} {2} {3} ::: 6 7 ::: 4 5 ::: 1 2 3
             parallel echo {1} {2} {3} :::: <(seq 6 7) <(seq 4 5) \
               :::: <(seq 1 3)
             parallel -a <(seq 6 7) echo {1} {2} {3} :::: <(seq 4 5) \
               :::: <(seq 1 3)
             parallel -a <(seq 6 7) -a <(seq 4 5) echo {1} {2} {3} \
               ::: 1 2 3
             seq 6 7 | parallel -a - -a <(seq 4 5) echo {1} {2} {3} \
               ::: 1 2 3
             seq 4 5 | parallel echo {1} {2} {3} :::: <(seq 6 7) - \
               ::: 1 2 3

           See also: --arg-sep --arg-file :::: :::+ ::::+ --link

       :::+ arguments
           Like ::: but linked like --link to the previous input source.

           Contrary to --link, values do not wrap: The shortest input source determines the
           length.

           Example:

             parallel echo ::: a b c :::+ 1 2 3 ::: X Y :::+ 11 22

           See also: ::::+ --link

       :::: argfiles
           Another way to write --arg-file argfile1 --arg-file argfile2 ...

           ::: and :::: can be mixed.

           See also: --arg-file ::: ::::+ --link

       ::::+ argfiles
           Like :::: but linked like --link to the previous input source.

           Contrary to --link, values do not wrap: The shortest input source determines the
           length.

           See also: --arg-file :::+ --link

       --null
       -0  Use NUL as delimiter.

           Normally input lines will end in \n (newline). If they end in \0 (NUL), then use this
           option. It is useful for processing arguments that may contain \n (newline).

           Shorthand for --delimiter '\0'.

           See also: --delimiter

       --arg-file input-file
       -a input-file
           Use input-file as input source.

           If multiple --arg-file are given, each input-file will be treated as an input source,
           and all combinations of input sources will be generated. E.g. The file foo contains 1
           2, the file bar contains a b c.  -a foo -a bar will result in the combinations (1,a)
           (1,b) (1,c) (2,a) (2,b) (2,c). This is useful for replacing nested for-loops.

           If input-file starts with + the file will be linked to the previous --arg-file E.g.
           The file foo contains 1 2, the file bar contains a b.  -a foo -a +bar will result in
           the combinations (1,a) (2,b) like --link instead of generating all combinations.

           See also: --link {n} :::: ::::+ :::

       --arg-file-sep sep-str
           Use sep-str instead of :::: as separator string between command and argument files.

           Useful if :::: is used for something else by the command.

           See also: ::::

       --arg-sep sep-str
           Use sep-str instead of ::: as separator string.

           Useful if ::: is used for something else by the command.

           Also useful if you command uses ::: but you still want to read arguments from stdin
           (standard input): Simply change --arg-sep to a string that is not in the command line.

           See also: :::

       --bar
           Show progress as a progress bar.

           In the bar is shown: % of jobs completed, estimated seconds left, and number of jobs
           started.

           It is compatible with zenity:

             seq 1000 | parallel -j30 --bar '(echo {};sleep 0.1)' \
               2> >(perl -pe 'BEGIN{$/="\r";$|=1};s/\r/\n/g' |
                    zenity --progress --auto-kill) | wc

           See also: --eta --progress --total-jobs

       --basefile file
       --bf file
           file will be transferred to each sshlogin before first job is started.

           It will be removed if --cleanup is active. The file may be a script to run or some
           common base data needed for the job.  Multiple --bf can be specified to transfer more
           basefiles. The file will be transferred the same way as --transferfile.

           See also: --sshlogin --transfer --return --cleanup --workdir

       --basenamereplace replace-str
       --bnr replace-str
           Use the replacement string replace-str instead of {/} for basename of input line.

           See also: {/}

       --basenameextensionreplace replace-str
       --bner replace-str
           Use the replacement string replace-str instead of {/.} for basename of input line
           without extension.

           See also: {/.}

       --bin binexpr
           Use binexpr as binning key and bin input to the jobs.

           binexpr is [column number|column name] [perlexpression] e.g.:

             3
             Address
             3 $_%=100
             Address s/\D//g

           Each input line is split using --colsep. The value of the column is put into $_, the
           perl expression is executed, the resulting value is is the job slot that will be given
           the line. If the value is bigger than the number of jobslots the value will be modulo
           number of jobslots.

           This is similar to --shard but the hashing algorithm is a simple modulo, which makes
           it predictible which jobslot will receive which value.

           The performance is in the order of 100K rows per second. Faster if the bincol is small
           (<10), slower if it is big (>100).

           --bin requires --pipe and a fixed numeric value for --jobs.

           See also: SPREADING BLOCKS OF DATA --group-by --round-robin --shard

       --bg
           Run command in background.

           GNU parallel will normally wait for the completion of a job. With --bg GNU parallel
           will not wait for completion of the command before exiting.

           This is the default if --semaphore is set.

           Implies --semaphore.

           See also: --fg man sem

       --block size
       --block-size size
           Size of block in bytes to read at a time.

           The size can be postfixed with K, M, G, T, P, k, m, g, t, or p.

           GNU parallel tries to meet the block size but can be off by the length of one record.
           For performance reasons size should be bigger than a two records. GNU parallel will
           warn you and automatically increase the size if you choose a size that is too small.

           If you use -N, --block should be bigger than N+1 records.

           size defaults to 1M.

           When using --pipe-part a negative block size is not interpreted as a blocksize but as
           the number of blocks each jobslot should have. So this will run 10*5 = 50 jobs in
           total:

             parallel --pipe-part -a myfile --block -10 -j5 wc

           This is an efficient alternative to --round-robin because data is never read by GNU
           parallel, but you can still have very few jobslots process large amounts of data.

           See also: UNIT PREFIX -N --pipe --pipe-part --round-robin --block-timeout

       --block-timeout duration
       --bt duration
           Timeout for reading block when using --pipe.

           If it takes longer than duration to read a full block, use the partial block read so
           far.

           duration is in seconds, but can be postfixed with s, m, h, or d.

           See also: TIME POSTFIXES --pipe --block

       --cat
           Create a temporary file with content.

           Normally --pipe/--pipe-part will give data to the program on stdin (standard input).
           With --cat GNU parallel will create a temporary file with the name in {}, so you can
           do: parallel --pipe --cat wc {}.

           Implies --pipe unless --pipe-part is used.

           See also: --pipe --pipe-part --fifo

       --cleanup
           Remove transferred files.

           --cleanup will remove the transferred files on the remote computer after processing is
           done.

             find log -name '*gz' | parallel \
               --sshlogin server.example.com --transferfile {} \
               --return {.}.bz2 --cleanup "zcat {} | bzip -9 >{.}.bz2"

           With --transferfile {} the file transferred to the remote computer will be removed on
           the remote computer. Directories on the remote computer containing the file will be
           removed if they are empty.

           With --return the file transferred from the remote computer will be removed on the
           remote computer. Directories on the remote computer containing the file will be
           removed if they are empty.

           --cleanup is ignored when not used with --basefile, --transfer, --transferfile or
           --return.

           See also: --basefile --transfer --transferfile --sshlogin --return

       --color
           Colour output.

           Colour the output. Each job gets its own colour combination (background+foreground).

           --color is ignored when using -u.

           See also: --color-failed

       --color-failed
       --cf
           Colour the output from failing jobs white on red.

           Useful if you have a lot of jobs and want to focus on the failing jobs.

           --color-failed is ignored when using -u, --line-buffer and unreliable when using
           --latest-line.

           See also: --color

       --colsep regexp
       -C regexp
           Column separator.

           The input will be treated as a table with regexp separating the columns. The n'th
           column can be accessed using {n} or {n.}. E.g. {3} is the 3rd column.

           If there are more input sources, each input source will be separated, but the columns
           from each input source will be linked.

             parallel --colsep '-' echo {4} {3} {2} {1} \
               ::: A-B C-D ::: e-f g-h

           --colsep implies --trim rl, which can be overridden with --trim n.

           regexp is a Perl Regular Expression: https://perldoc.perl.org/perlre.html

           See also: --csv {n} --trim --link

       --combineexec name (beta testing)
       --combine-executable name (beta testing)
           Combine GNU parallel with another program into a single executable.

           Let us say you have developed myprg which takes a single argument. You do not want to
           parallelize it yourself.

           You could write a wrapper that uses GNU parallel called myparprg:

              #!/bin/sh

              parallel myprg ::: "$@"

           But for others to use this, they need to install: GNU parallel, myprg, and myparprg.

           It would be easier to install if all could be packed into a single executable.

           If myprg is written in shell, you can use --embed.

           If myprg is a binary you can use --combineexec.

           Here we use gzip as example:

              parallel --combineexec pargzip gzip -9 :::

           You can now do:

              ./pargzip foo bar baz

           If you want to pass options to gzip you can do:

              parallel --combineexec pargzip gzip

           Followed by:

              ./pargzip -1 ::: foo bar baz

           See also: --embed --shebang --shebang-wrap

       --compress
           Compress temporary files.

           If the output is big and very compressible this will take up less disk space in
           $TMPDIR and possibly be faster due to less disk I/O.

           GNU parallel will try pzstd, lbzip2, pbzip2, zstd, pigz, lz4, lzop, plzip, lzip, lrz,
           gzip, pxz, lzma, bzip2, xz, clzip, in that order, and use the first available.

           GNU parallel will use up to 8 processes per job waiting to be printed. See man
           parallel_design for details.

           See also: --compress-program

       --compress-program prg
       --decompress-program prg
           Use prg for (de)compressing temporary files.

           It is assumed that prg -dc will decompress stdin (standard input) to stdout (standard
           output) unless --decompress-program is given.

           See also: --compress

       --csv
           Treat input as CSV-format.

           --colsep sets the field delimiter. It works very much like --colsep except it deals
           correctly with quoting. Compare:

              echo '"1 big, 2 small","2""x4"" plank",12.34' |
                parallel --csv echo {1} of {2} at {3}

              echo '"1 big, 2 small","2""x4"" plank",12.34' |
                parallel --colsep ',' echo {1} of {2} at {3}

           Even quoted newlines are parsed correctly:

              (echo '"Start of field 1 with newline'
               echo 'Line 2 in field 1";value 2') |
                parallel --csv --colsep ';' echo Field 1: {1} Field 2: {2}

           When used with --pipe only pass full CSV-records.

           See also: --pipe --link {n} --colsep --header

       --ctag (obsolete: use --color --tag)
           Color tag.

           If the values look very similar looking at the output it can be hard to tell when a
           new value is used. --ctag gives each value a random color.

           See also: --color --tag

       --ctagstring str (obsolete: use --color --tagstring)
           Color tagstring.

           See also: --color --ctag --tagstring

       --delay duration
           Delay starting next job by duration.

           GNU parallel will not start another job for the next duration.

           duration is in seconds, but can be postfixed with s, m, h, or d.

           If you append 'auto' to duration (e.g. 13m3sauto) GNU parallel will automatically try
           to find the optimal value: If a job fails, duration is increased by 30%. If a job
           succeeds, duration is decreased by 10%.

           See also: TIME POSTFIXES --retries --ssh-delay

       --delimiter delim
       -d delim
           Input items are terminated by delim.

           The specified delimiter may be characters, C-style character escapes such as \n, or
           octal or hexadecimal escape codes.  Octal and hexadecimal escape codes are understood
           as for the printf command.

           See also: --colsep

       --dirnamereplace replace-str
       --dnr replace-str
           Use the replacement string replace-str instead of {//} for dirname of input line.

           See also: {//}

       --dry-run
           Print the job to run on stdout (standard output), but do not run the job.

           Use -v -v to include the wrapping that GNU parallel generates (for remote jobs,
           --tmux, --nice, --pipe, --pipe-part, --fifo and --cat). Do not count on this
           literally, though, as the job may be scheduled on another computer or the local
           computer if : is in the list.

           See also: -v

       -E eof-str
           Set the end of file string to eof-str.

           If the end of file string occurs as a line of input, the rest of the input is not
           read.  If neither -E nor -e is used, no end of file string is used.

       --eof[=eof-str]
       -e[eof-str]
           This option is a synonym for the -E option.

           Use -E instead, because it is POSIX compliant for xargs while this option is not.  If
           eof-str is omitted, there is no end of file string.  If neither -E nor -e is used, no
           end of file string is used.

       --embed
           Embed GNU parallel in a shell script.

           If you need to distribute your script to someone who does not want to install GNU
           parallel you can embed GNU parallel in your own shell script:

             parallel --embed > new_script

           After which you add your code at the end of new_script. This is tested on ash, bash,
           dash, ksh, sh, and zsh.

       --env var
           Copy exported environment variable var.

           This will copy var to the environment that the command is run in. This is especially
           useful for remote execution.

           In Bash var can also be a Bash function - just remember to export -f the function.

           The variable '_' is special. It will copy all exported environment variables except
           for the ones mentioned in ~/.parallel/ignored_vars.

           To copy the full environment (both exported and not exported variables, arrays, and
           functions) use env_parallel.

           See also: --record-env --session --sshlogin command env_parallel

       --eta
           Show the estimated number of seconds before finishing.

           This forces GNU parallel to read all jobs before starting to find the number of jobs
           (unless you use --total-jobs). GNU parallel normally only reads the next job to run.

           The estimate is based on the runtime of finished jobs, so the first estimate will only
           be shown when the first job has finished.

           Implies --progress.

           See also: --bar --progress --total-jobs

       --fg
           Run command in foreground.

           With --tmux and --tmuxpane GNU parallel will start tmux in the foreground.

           With --semaphore GNU parallel will run the command in the foreground (opposite --bg),
           and wait for completion of the command before exiting. Exit code will be that of the
           command.

           See also: --bg man sem

       --fifo
           Create a temporary fifo with content.

           Normally --pipe and --pipe-part will give data to the program on stdin (standard
           input). With --fifo GNU parallel will create a temporary fifo with the name in {}, so
           you can do:

             parallel --pipe --fifo wc {}

           Beware: If the fifo is never opened for reading, the job will block forever:

             seq 1000000 | parallel --fifo echo This will block forever
             seq 1000000 | parallel --fifo 'echo This will not block < {}'

           By using --fifo instead of --cat you may save I/O as --cat will write to a temporary
           file, whereas --fifo will not.

           Implies --pipe unless --pipe-part is used.

           See also: --cat --pipe --pipe-part

       --filter filter
           Only run jobs where filter is true.

           filter can contain replacement strings and Perl code. Example:

             parallel --filter '{1}+{2}+{3} < 10' echo {1},{2},{3} \
               ::: {1..10} ::: {3..8} ::: {3..10}

           Outputs: 1,3,3 1,3,4 1,3,5 1,4,3 1,4,4 1,5,3 2,3,3 2,3,4 2,4,3 3,3,3

             parallel --filter '{1} < {2}*{2}' echo {1},{2} \
               ::: {1..10} ::: {1..3}

           Outputs: 1,2 1,3 2,2 2,3 3,2 3,3 4,3 5,3 6,3 7,3 8,3

             parallel --filter '{choose_k}' --plus echo {1},{2},{3} \
               ::: {1..5} ::: {1..5} ::: {1..5}

           Outputs: 1,2,3 1,2,4 1,2,5 1,3,4 1,3,5 1,4,5 2,3,4 2,3,5 2,4,5 3,4,5

           See also: skip() --no-run-if-empty {choose_k}

       --filter-hosts
           Remove down hosts.

           For each remote host: check that login through ssh works. If not: do not use this
           host.

           For performance reasons, this check is performed only at the start and every time
           --sshloginfile is changed. If an host goes down after the first check, it will go
           undetected until --sshloginfile is changed; --retries can be used to mitigate this.

           Currently you can not put --filter-hosts in a profile, $PARALLEL, /etc/parallel/config
           or similar. This is because GNU parallel uses GNU parallel to compute this, so you
           will get an infinite loop. This will likely be fixed in a later release.

           See also: --sshloginfile --sshlogin --retries

       --gnu
           Behave like GNU parallel.

           This option historically took precedence over --tollef. The --tollef option is now
           retired, and therefore may not be used. --gnu is kept for compatibility, but does
           nothing.

       --group
           Group output.

           Output from each job is grouped together and is only printed when the command is
           finished. Stdout (standard output) first followed by stderr (standard error).

           This takes in the order of 0.5ms CPU time per job and depends on the speed of your
           disk for larger output.

           --group is the default.

           See also: --line-buffer --ungroup --tag

       --group-by val
           Group input by value.

           Combined with --pipe/--pipe-part --group-by groups lines with the same value into a
           record.

           The value can be computed from the full line or from a single column.

           val can be:

            column number Use the value in the column numbered.

            column name   Treat the first line as a header and use the value in the column named.

                          (Not supported with --pipe-part).

            perl expression
                          Run the perl expression and use $_ as the value.

            column number perl expression
                          Put the value of the column put in $_, run the perl expression, and use
                          $_ as the value.

            column name perl expression
                          Put the value of the column put in $_, run the perl expression, and use
                          $_ as the value.

                          (Not supported with --pipe-part).

           Example:

             UserID, Consumption
             123,    1
             123,    2
             12-3,   1
             221,    3
             221,    1
             2/21,   5

           If you want to group 123, 12-3, 221, and 2/21 into 4 records and pass one record at a
           time to wc:

             tail -n +2 table.csv | \
               parallel --pipe --colsep , --group-by 1 -kN1 wc

           Make GNU parallel treat the first line as a header:

             cat table.csv | \
               parallel --pipe --colsep , --header : --group-by 1 -kN1 wc

           Address column by column name:

             cat table.csv | \
               parallel --pipe --colsep , --header : --group-by UserID -kN1 wc

           If 12-3 and 123 are really the same UserID, remove non-digits in UserID when grouping:

             cat table.csv | parallel --pipe --colsep , --header : \
               --group-by 'UserID s/\D//g' -kN1 wc

           See also: SPREADING BLOCKS OF DATA --pipe --pipe-part --bin --shard --round-robin

       --help
       -h  Print a summary of the options to GNU parallel and exit.

       --halt-on-error val
       --halt val
           When should GNU parallel terminate?

           In some situations it makes no sense to run all jobs. GNU parallel should simply stop
           as soon as a condition is met.

           val defaults to never, which runs all jobs no matter what.

           val can also take on the form of when,why.

           when can be 'now' which means kill all running jobs and halt immediately, or it can be
           'soon' which means wait for all running jobs to complete, but start no new jobs.

           why can be 'fail=X', 'fail=Y%', 'success=X', 'success=Y%', 'done=X', or 'done=Y%'
           where X is the number of jobs that has to fail, succeed, or be done before halting,
           and Y is the percentage of jobs that has to fail, succeed, or be done before halting.

           Example:

            --halt now,fail=1     exit when a job has failed. Kill running jobs.

            --halt soon,fail=3    exit when 3 jobs have failed, but wait for running jobs to
                                  complete.

            --halt soon,fail=3%   exit when 3% of the jobs have failed, but wait for running jobs
                                  to complete.

            --halt now,success=1  exit when a job has succeeded. Kill running jobs.

            --halt soon,success=3 exit when 3 jobs have succeeded, but wait for running jobs to
                                  complete.

            --halt now,success=3% exit when 3% of the jobs have succeeded. Kill running jobs.

            --halt now,done=1     exit when a job has finished. Kill running jobs.

            --halt soon,done=3    exit when 3 jobs have finished, but wait for running jobs to
                                  complete.

            --halt now,done=3%    exit when 3% of the jobs have finished. Kill running jobs.

           For backwards compatibility these also work:

           0           never

           1           soon,fail=1

           2           now,fail=1

           -1          soon,success=1

           -2          now,success=1

           1-99%       soon,fail=1-99%

       --header regexp
           Use regexp as header.

           For normal usage the matched header (typically the first line: --header '.*\n') will
           be split using --colsep (which will default to '\t') and column names can be used as
           replacement variables: {column name}, {column name/}, {column name//}, {column
           name/.}, {column name.}, {=column name perl expression =}, ..

           For --pipe the matched header will be prepended to each output.

           --header : is an alias for --header '.*\n'.

           If regexp is a number, it is a fixed number of lines.

           --header 0 is special: It will make replacement strings for files given with
           --arg-file or ::::. It will make {foo/bar} for the file foo/bar.

           See also: --colsep --pipe --pipe-part --arg-file

       --hostgroups
       --hgrp
           Enable hostgroups on arguments.

           If an argument contains '@' the string after '@' will be removed and treated as a list
           of hostgroups on which this job is allowed to run. If there is no --sshlogin with a
           corresponding group, the job will run on any hostgroup.

           Example:

             parallel --hostgroups \
               --sshlogin @grp1/myserver1 -S @grp1+grp2/myserver2 \
               --sshlogin @grp3/myserver3 \
               echo ::: my_grp1_arg@grp1 arg_for_grp2@grp2 third@grp1+grp3

           my_grp1_arg may be run on either myserver1 or myserver2, third may be run on either
           myserver1 or myserver3, but arg_for_grp2 will only be run on myserver2.

           See also: --sshlogin $PARALLEL_HOSTGROUPS $PARALLEL_ARGHOSTGROUPS

       -I replace-str
           Use the replacement string replace-str instead of {}.

           See also: {}

       --replace [replace-str]
       -i [replace-str]
           This option is deprecated; use -I instead.

           This option is a synonym for -Ireplace-str if replace-str is specified, and for -I {}
           otherwise.

           See also: {}

       --joblog logfile
       --jl logfile
           Logfile for executed jobs.

           Save a list of the executed jobs to logfile in the following TAB separated format:
           sequence number, sshlogin, start time as seconds since epoch, run time in seconds,
           bytes in files transferred, bytes in files returned, exit status, signal, and command
           run.

           For --pipe bytes transferred and bytes returned are number of input and output of
           bytes.

           If logfile is prepended with '+' log lines will be appended to the logfile.

           To convert the times into ISO-8601 strict do:

             cat logfile | perl -a -F"\t" -ne \
               'chomp($F[2]=`date -d \@$F[2] +%FT%T`); print join("\t",@F)'

           If the host is long, you can use column -t to pretty print it:

             cat joblog | column -t

           See also: --resume --resume-failed

       --jobs num
       -j num
       --max-procs num
       -P num
           Number of jobslots on each machine.

           Run up to num jobs in parallel. Default is 100%.

           num    Run up to num jobs in parallel.

           0      Run as many as possible (this can take a while to determine).

                  Due to a bug -j 0 will also evaluate replacement strings twice up to the number
                  of joblots:

                    # This will not count from 1 but from number-of-jobslots
                    seq 10000 | parallel -j0   echo '{= $_ = $foo++; =}' | head
                    # This will count from 1
                    seq 10000 | parallel -j100 echo '{= $_ = $foo++; =}' | head

           num%   Multiply the number of CPU threads by num percent. E.g. 100% means one job per
                  CPU thread on each machine.

           +num   Add num to the number of CPU threads.

           -num   Subtract num from the number of CPU threads.

           expr   Evaluate expr. E.g. '12/2' to get 6, '+25%' gives the same as '125%', or
                  complex expressions like '+3*log(55)%' which means: multiply 3 by log(55),
                  multiply that by the number of CPU threads and divide by 100, add this to the
                  number of CPU threads.

                  An expression that evalutates to less that 1 is replaced with 1.

           procfile
                  Read parameter from file.

                  Use the content of procfile as parameter for -j. E.g. procfile could contain
                  the string 100% or +2 or 10.

                  If procfile is changed when a job completes, procfile is read again and the new
                  number of jobs is computed. If the number is lower than before, running jobs
                  will be allowed to finish but new jobs will not be started until the wanted
                  number of jobs has been reached.  This makes it possible to change the number
                  of simultaneous running jobs while GNU parallel is running.

           If the evaluated number is less than 1 then 1 will be used.

           If --semaphore is set, the default is 1 thus making a mutex.

           See also: --use-cores-instead-of-threads --use-sockets-instead-of-threads

       --keep-order
       -k  Keep sequence of output same as the order of input.

           Normally the output of a job will be printed as soon as the job completes. Try this to
           see the difference:

             parallel -j4 sleep {}\; echo {} ::: 2 1 4 3
             parallel -j4 -k sleep {}\; echo {} ::: 2 1 4 3

           If used with --onall or --nonall the output will grouped by sshlogin in sorted order.

           --keep-order cannot keep the output order when used with --pipe --round-robin. Here it
           instead means, that the jobslots will get the same blocks as input in the same order
           in every run if the input is kept the same. Run each of these twice and compare:

             seq 10000000 | parallel --pipe --round-robin 'sleep 0.$RANDOM; wc'
             seq 10000000 | parallel --pipe -k --round-robin 'sleep 0.$RANDOM; wc'

           -k only affects the order in which the output is printed - not the order in which jobs
           are run.

           See also: --group --line-buffer

       -L recsize
           When used with --pipe: Read records of recsize.

           When used otherwise: Use at most recsize nonblank input lines per command line.
           Trailing blanks cause an input line to be logically continued on the next input line.

           -L 0 means read one line, but insert 0 arguments on the command line.

           recsize can be postfixed with K, M, G, T, P, k, m, g, t, or p.

           Implies -X unless -m, --xargs, or --pipe is set.

           See also: UNIT PREFIX -N --max-lines --block -X -m --xargs --pipe

       --max-lines [recsize]
       -l[recsize]
           When used with --pipe: Read records of recsize lines.

           When used otherwise: Synonym for the -L option.  Unlike -L, the recsize argument is
           optional.  If recsize is not specified, it defaults to one.  The -l option is
           deprecated since the POSIX standard specifies -L instead.

           -l 0 is an alias for -l 1.

           Implies -X unless -m, --xargs, or --pipe is set.

           See also: UNIT PREFIX -N --block -X -m --xargs --pipe

       --limit "command args"
           Dynamic job limit.

           Before starting a new job run command with args. The exit value of command determines
           what GNU parallel will do:

           0   Below limit. Start another job.

           1   Over limit. Start no jobs.

           2   Way over limit. Kill the youngest job.

           You can use any shell command. There are 3 predefined commands:

           "io n"    Limit for I/O. The amount of disk I/O will be computed as a value 0-100,
                     where 0 is no I/O and 100 is at least one disk is 100% saturated.

           "load n"  Similar to --load.

           "mem n"   Similar to --memfree.

           See also: --memfree --load

       --latest-line
       --ll
           Print the lastest line. Each job gets a single line that is updated with the lastest
           output from the job.

           Example:

             slow_seq() {
               seq "$@" |
                 perl -ne '$|=1; for(split//){ print; select($a,$a,$a,0.03);}'
             }
             export -f slow_seq
             parallel --shuf -j99 --ll --tag --bar --color slow_seq {} ::: {1..300}

           See also: --line-buffer

       --line-buffer
       --lb
           Buffer output on line basis.

           --group will keep the output together for a whole job. --ungroup allows output to
           mixup with half a line coming from one job and half a line coming from another job.
           --line-buffer fits between these two: GNU parallel will print a full line, but will
           allow for mixing lines of different jobs.

           --line-buffer takes more CPU power than both --group and --ungroup, but can be much
           faster than --group if the CPU is not the limiting factor.

           Normally --line-buffer does not buffer on disk, and can thus process an infinite
           amount of data, but it will buffer on disk when combined with: --keep-order,
           --results, --compress, and --files. This will make it as slow as --group and will
           limit output to the available disk space.

           With --keep-order --line-buffer will output lines from the first job continuously
           while it is running, then lines from the second job while that is running. It will
           buffer full lines, but jobs will not mix. Compare:

             parallel -j0 'echo [{};sleep {};echo {}]' ::: 1 3 2 4
             parallel -j0 --lb 'echo [{};sleep {};echo {}]' ::: 1 3 2 4
             parallel -j0 -k --lb 'echo [{};sleep {};echo {}]' ::: 1 3 2 4

           See also: --group --ungroup --keep-order --tag

       --link
       --xapply
           Link input sources.

           Read multiple input sources like the command xapply. If multiple input sources are
           given, one argument will be read from each of the input sources. The arguments can be
           accessed in the command as {1} .. {n}, so {1} will be a line from the first input
           source, and {6} will refer to the line with the same line number from the 6th input
           source.

           Compare these two:

             parallel echo {1} {2} ::: 1 2 3 ::: a b c
             parallel --link echo {1} {2} ::: 1 2 3 ::: a b c

           Arguments will be recycled if one input source has more arguments than the others:

             parallel --link echo {1} {2} {3} \
               ::: 1 2 ::: I II III ::: a b c d e f g

           See also: --header :::+ ::::+

       --load max-load
           Only start jobs if load is less than max-load.

           Do not start new jobs on a given computer unless the number of running processes on
           the computer is less than max-load. max-load uses the same syntax as --jobs, so 100%
           for one per CPU is a valid setting. Only difference is 0 which is interpreted as 0.01.

           See also: --limit --jobs

       --controlmaster
       -M  Use ssh's ControlMaster to make ssh connections faster.

           Useful if jobs run remote and are very fast to run. This is disabled for sshlogins
           that specify their own ssh command.

           See also: --ssh --sshlogin

       -m  Multiple arguments.

           Insert as many arguments as the command line length permits. If multiple jobs are
           being run in parallel: distribute the arguments evenly among the jobs. Use -j1 or
           --xargs to avoid this.

           If {} is not used the arguments will be appended to the line.  If {} is used multiple
           times each {} will be replaced with all the arguments.

           Support for -m with --sshlogin is limited and may fail.

           If in doubt use -X as that will most likely do what is needed.

           See also: -X --xargs

       --memfree size
           Minimum memory free when starting another job.

           The size can be postfixed with K, M, G, T, P, k, m, g, t, or p.

           If the jobs take up very different amount of RAM, GNU parallel will only start as many
           as there is memory for. If less than size bytes are free, no more jobs will be
           started. If less than 50% size bytes are free, the youngest job will be killed (as per
           --term-seq), and put back on the queue to be run later.

           --retries must be set to determine how many times GNU parallel should retry a given
           job.

           See also: UNIT PREFIX --term-seq --retries --memsuspend

       --memsuspend size
           Suspend jobs when there is less memory available.

           If the available memory falls below 2 * size, GNU parallel will suspend some of the
           running jobs. If the available memory falls below size, only one job will be running.

           If a single job fits in the given size, all jobs will complete without running out of
           memory. If you have swap available, you can usually lower size to around half the size
           of a single job - with the slight risk of swapping a little.

           Jobs will be resumed when more RAM is available - typically when the oldest job
           completes.

           --memsuspend only works on local jobs because there is no obvious way to suspend
           remote jobs.

           size can be postfixed with K, M, G, T, P, k, m, g, t, or p.

           See also: UNIT PREFIX --memfree

       --minversion version
           Print the version GNU parallel and exit.

           If the current version of GNU parallel is less than version the exit code is 255.
           Otherwise it is 0.

           This is useful for scripts that depend on features only available from a certain
           version of GNU parallel:

              parallel --minversion 20170422 &&
                echo halt done=50% supported from version 20170422 &&
                parallel --halt now,done=50% echo ::: {1..100}

           See also: --version

       --max-args max-args
       -n max-args
           Use at most max-args arguments per command line.

           Fewer than max-args arguments will be used if the size (see the -s option) is
           exceeded, unless the -x option is given, in which case GNU parallel will exit.

           -n 0 means read one argument, but insert 0 arguments on the command line.

           max-args can be postfixed with K, M, G, T, P, k, m, g, t, or p (see UNIT PREFIX).

           Implies -X unless -m is set.

           See also: -X -m --xargs --max-replace-args

       --max-replace-args max-args
       -N max-args
           Use at most max-args arguments per command line.

           Like -n but also makes replacement strings {1} .. {max-args} that represents argument
           1 .. max-args. If too few args the {n} will be empty.

           -N 0 means read one argument, but insert 0 arguments on the command line.

           This will set the owner of the homedir to the user:

             tr ':' '\n' < /etc/passwd | parallel -N7 chown {1} {6}

           Implies -X unless -m or --pipe is set.

           max-args can be postfixed with K, M, G, T, P, k, m, g, t, or p.

           When used with --pipe -N is the number of records to read. This is somewhat slower
           than --block.

           See also: UNIT PREFIX --pipe --block -m -X --max-args

       --nonall
           --onall with no arguments.

           Run the command on all computers given with --sshlogin but take no arguments. GNU
           parallel will log into --jobs number of computers in parallel and run the job on the
           computer. -j adjusts how many computers to log into in parallel.

           This is useful for running the same command (e.g. uptime) on a list of servers.

           See also: --onall --sshlogin

       --onall
           Run all the jobs on all computers given with --sshlogin.

           GNU parallel will log into --jobs number of computers in parallel and run one job at a
           time on the computer. The order of the jobs will not be changed, but some computers
           may finish before others.

           When using --group the output will be grouped by each server, so all the output from
           one server will be grouped together.

           --joblog will contain an entry for each job on each server, so there will be several
           job sequence 1.

           See also: --nonall --sshlogin

       --open-tty
       -o  Open terminal tty.

           Similar to --tty but does not set --jobs or --ungroup.

           See also: --tty

       --output-as-files
       --outputasfiles
       --files
       --files0
           Save output to files.

           Instead of printing the output to stdout (standard output) the output of each job is
           saved in a file and the filename is then printed.

           --files0 uses NUL (\0) instead of newline (\n) as separator.

           See also: --results

       --pipe
       --spreadstdin
           Spread input to jobs on stdin (standard input).

           Read a block of data from stdin (standard input) and give one block of data as input
           to one job.

           The block size is determined by --block (default: 1M).

           Except for the first and last record GNU parallel only passes full records to the job.
           The strings --recstart and --recend determine where a record starts and ends: The
           border between two records is defined as --recend immediately followed by --recstart.
           GNU parallel splits exactly after --recend and before --recstart. The block will have
           the last partial record removed before the block is passed on to the job. The partial
           record will be prepended to next block.

           You can limit the number of records to be passed with -N, and set the record size with
           -L.

           --pipe maxes out at around 1 GB/s input, and 100 MB/s output. If performance is
           important use --pipe-part.

           --fifo and --cat will give stdin (standard input) on a fifo or a temporary file.

           If data is arriving slowly, you can use --block-timeout to finish reading a block
           early.

           The data can be spread between the jobs in specific ways using --round-robin, --bin,
           --shard, --group-by. See the section: SPREADING BLOCKS OF DATA

           See also: --block --block-timeout --recstart --recend --fifo --cat --pipe-part -N -L
           --round-robin

       --pipe-part
           Pipe parts of a physical file.

           --pipe-part works similar to --pipe, but is much faster. 5 GB/s can easily be
           delivered.

           --pipe-part has a few limitations:

           •  The file must be a normal file or a block device (technically it must be seekable)
              and must be given using --arg-file or ::::. The file cannot be a pipe, a fifo, or a
              stream as they are not seekable.

              If using a block device with lot of NUL bytes, remember to set --recend ''.

           •  Record counting (-N) and line counting (-L/-l) do not work. Instead use --recstart
              and --recend to determine where records end.

           See also: --pipe --recstart --recend --arg-file ::::

       --plain
           Ignore --profile, $PARALLEL, and ~/.parallel/config.

           Ignore any --profile, $PARALLEL, and ~/.parallel/config to get full control on the
           command line (used by GNU parallel internally when called with --sshlogin).

           See also: --profile

       --plus
           Add more replacement strings.

           Activate additional replacement strings: {+/} {+.} {+..} {+...} {..} {...} {/..}
           {/...} {##}. The idea being that '{+foo}' matches the opposite of '{foo}' so that:

           {} = {+/}/{/} = {.}.{+.} = {+/}/{/.}.{+.}  = {..}.{+..} = {+/}/{/..}.{+..} =
           {...}.{+...} = {+/}/{/...}.{+...}

           {##} is the total number of jobs to be run. It is incompatible with -X/-m/--xargs.

           {0%} zero-padded jobslot.

           {0#} zero-padded sequence number.

           {slot-1} jobslot - 1 (i.e. counting from 0). -1 can be any perl expression:
           {slot**2-1} = slot*slot-1.

           {seq-1} sequence number - 1 (i.e. counting from 0). -1 can be any perl expression.

           {choose_k} is inspired by n choose k: Given a list of n elements, choose k. k is the
           number of input sources and n is the number of arguments in an input source.  The
           content of the input sources must be the same and the arguments must be unique.

           {uniq} skips jobs where values from two input sources are the same.

           Shorthands for variables:

             {slot}         $PARALLEL_JOBSLOT (see {%})
             {sshlogin}     $PARALLEL_SSHLOGIN
             {host}         $PARALLEL_SSHHOST
             {agrp}         $PARALLEL_ARGHOSTGROUPS
             {hgrp}         $PARALLEL_HOSTGROUPS

           The following dynamic replacement strings are also activated. They are inspired by
           bash's parameter expansion:

             {:-str}        str if the value is empty
             {:num}         remove the first num characters
             {:pos:len}     substring from position pos length len
             {#regexp}      remove prefix regexp (non-greedy)
             {##regexp}     remove prefix regexp (greedy)
             {%regexp}      remove postfix regexp (non-greedy)
             {%%regexp}     remove postfix regexp (greedy)
             {/regexp/str}  replace one regexp with str
             {//regexp/str} replace every regexp with str
             {^str}         uppercase str if found at the start
             {^^str}        uppercase str
             {,str}         lowercase str if found at the start
             {,,str}        lowercase str

           See also: --rpl {}

       --process-slot-var varname
           Set the environment variable varname to the jobslot number-1.

             seq 10 | parallel --process-slot-var=name echo '$name' {}

       --progress
           Show progress of computations.

           List the computers involved in the task with number of CPUs detected and the max
           number of jobs to run. After that show progress for each computer: number of running
           jobs, number of completed jobs, and percentage of all jobs done by this computer. The
           percentage will only be available after all jobs have been scheduled as GNU parallel
           only read the next job when ready to schedule it - this is to avoid wasting time and
           memory by reading everything at startup.

           By sending GNU parallel SIGUSR2 you can toggle turning on/off --progress on a running
           GNU parallel process.

           See also: --eta --bar

       --max-line-length-allowed
           Print maximal command line length.

           Print the maximal number of characters allowed on the command line and exit (used by
           GNU parallel itself to determine the line length on remote computers).

           See also: --show-limits

       --number-of-cpus (obsolete)
           Print the number of physical CPU cores and exit.

       --number-of-cores
           Print the number of physical CPU cores and exit (used by GNU parallel itself to
           determine the number of physical CPU cores on remote computers).

           See also: --number-of-sockets --number-of-threads --use-cores-instead-of-threads
           --jobs

       --number-of-sockets
           Print the number of filled CPU sockets and exit (used by GNU parallel itself to
           determine the number of filled CPU sockets on remote computers).

           See also: --number-of-cores --number-of-threads --use-sockets-instead-of-threads
           --jobs

       --number-of-threads
           Print the number of hyperthreaded CPU cores and exit (used by GNU parallel itself to
           determine the number of hyperthreaded CPU cores on remote computers).

           See also: --number-of-cores --number-of-sockets --jobs

       --no-keep-order
           Overrides an earlier --keep-order (e.g. if set in ~/.parallel/config).

       --nice niceness
           Run the command at this niceness.

           By default GNU parallel will run jobs at the same nice level as GNU parallel is
           started - both on the local machine and remote servers, so you are unlikely to ever
           use this option.

           Setting --nice will override this nice level. If the nice level is smaller than the
           current nice level, it will only affect remote jobs (e.g. if current level is 10 then
           --nice 5 will cause local jobs to be run at level 10, but remote jobs run at nice
           level 5).

       --interactive
       -p  Ask user before running a job.

           Prompt the user about whether to run each command line and read a line from the
           terminal.  Only run the command line if the response starts with 'y' or 'Y'.  Implies
           -t.

       --_parset type,varname
           Used internally by parset.

           Generate shell code to be eval'ed which will set the variable(s) varname. type can be
           'assoc' for associative array or 'var' for normal variables.

           The only supported use is as part of parset.

       --parens parensstring
           Use parensstring instead of {==}.

           Define start and end parenthesis for {=perl expression=}. The left and the right
           parenthesis can be multiple characters and are assumed to be the same length. The
           default is {==} giving {= as the start parenthesis and =} as the end parenthesis.

           Another useful setting is ,,,, which would make both parenthesis ,,:

             parallel --parens ,,,, echo foo is ,,s/I/O/g,, ::: FII

           See also: --rpl {=perl expression=}

       --profile profilename
       -J profilename
           Use profile profilename for options.

           This is useful if you want to have multiple profiles. You could have one profile for
           running jobs in parallel on the local computer and a different profile for running
           jobs on remote computers.

           profilename corresponds to the file ~/.parallel/profilename.

           You can give multiple profiles by repeating --profile. If parts of the profiles
           conflict, the later ones will be used.

           Default: ~/.parallel/config

           See also: PROFILE FILES

       --quote
       -q  Quote command.

           If your command contains special characters that should not be interpreted by the
           shell (e.g. ; \ | *), use --quote to escape these. The command must be a simple
           command (see man bash) without redirections and without variable assignments.

           Most people will not need this. Quoting is disabled by default.

           See also: QUOTING command --shell-quote uq() Q()

       --no-run-if-empty
       -r  Do not run empty input.

           If the stdin (standard input) only contains whitespace, do not run the command.

           If used with --pipe this is slow.

           See also: command --pipe --interactive

       --noswap
           Do not start job is computer is swapping.

           Do not start new jobs on a given computer if there is both swap-in and swap-out
           activity.

           The swap activity is only sampled every 10 seconds as the sampling takes 1 second to
           do.

           Swap activity is computed as (swap-in)*(swap-out) which in practice is a good value:
           swapping out is not a problem, swapping in is not a problem, but both swapping in and
           out usually indicates a problem.

           --memfree and --memsuspend may give better results, so try using those first.

           See also: --memfree --memsuspend

       --record-env
           Record exported environment.

           Record current exported environment variables in ~/.parallel/ignored_vars.  This will
           ignore variables currently set when using --env _. So you should set the
           variables/fuctions, you want to use after running --record-env.

           See also: --env --session env_parallel

       --recstart startstring
       --recend endstring
           Split record between endstring and startstring.

           If --recstart is given startstring will be used to split at record start.

           If --recend is given endstring will be used to split at record end.

           If both --recstart and --recend are given the combined string endstringstartstring
           will have to match to find a split position. This is useful if either startstring or
           endstring match in the middle of a record.

           If neither --recstart nor --recend are given, then --recend defaults to '\n'. To have
           no record separator (e.g. for binary files) use --recend "".

           --recstart and --recend are used with --pipe.

           Use --regexp to interpret --recstart and --recend as regular expressions. This is
           slow, however.

           Use --remove-rec-sep to remove --recstart and --recend before passing the block to the
           job.

           See also: --pipe --regexp --remove-rec-sep

       --regexp
           Use --regexp to interpret --recstart and --recend as regular expressions. This is
           slow, however.

           See also: --pipe --regexp --remove-rec-sep --recstart --recend

       --remove-rec-sep
       --removerecsep
       --rrs
           Remove record separator.

           Remove the text matched by --recstart and --recend before piping it to the command.

           Only used with --pipe/--pipe-part.

           See also: --pipe --regexp --pipe-part --recstart --recend

       --results name
       --res name
           Save the output into files.

           Simple string output dir

           If name does not contain replacement strings and does not end in .csv/.tsv, the output
           will be stored in a directory tree rooted at name.  Within this directory tree, each
           command will result in three files: name/<ARGS>/stdout and name/<ARGS>/stderr,
           name/<ARGS>/seq, where <ARGS> is a sequence of directories representing the header of
           the input source (if using --header :) or the number of the input source and
           corresponding values.

           E.g:

             parallel --header : --results foo echo {a} {b} \
               ::: a I II ::: b III IIII

           will generate the files:

             foo/a/II/b/III/seq
             foo/a/II/b/III/stderr
             foo/a/II/b/III/stdout
             foo/a/II/b/IIII/seq
             foo/a/II/b/IIII/stderr
             foo/a/II/b/IIII/stdout
             foo/a/I/b/III/seq
             foo/a/I/b/III/stderr
             foo/a/I/b/III/stdout
             foo/a/I/b/IIII/seq
             foo/a/I/b/IIII/stderr
             foo/a/I/b/IIII/stdout

           and

             parallel --results foo echo {1} {2} ::: I II ::: III IIII

           will generate the files:

             foo/1/II/2/III/seq
             foo/1/II/2/III/stderr
             foo/1/II/2/III/stdout
             foo/1/II/2/IIII/seq
             foo/1/II/2/IIII/stderr
             foo/1/II/2/IIII/stdout
             foo/1/I/2/III/seq
             foo/1/I/2/III/stderr
             foo/1/I/2/III/stdout
             foo/1/I/2/IIII/seq
             foo/1/I/2/IIII/stderr
             foo/1/I/2/IIII/stdout

           CSV file output

           If name ends in .csv/.tsv the output will be a CSV-file named name.

           .csv gives a comma separated value file. .tsv gives a TAB separated value file.

           -.csv/-.tsv are special: It will give the file on stdout (standard output).

           JSON file output

           If name ends in .json the output will be a JSON-file named name.

           -.json is special: It will give the file on stdout (standard output).

           Replacement string output file

           If name contains a replacement string and the replaced result does not end in /, then
           the standard output will be stored in a file named by this result. Standard error will
           be stored in the same file name with '.err' added, and the sequence number will be
           stored in the same file name with '.seq' added.

           E.g.

             parallel --results my_{} echo ::: foo bar baz

           will generate the files:

             my_bar
             my_bar.err
             my_bar.seq
             my_baz
             my_baz.err
             my_baz.seq
             my_foo
             my_foo.err
             my_foo.seq

           Replacement string output dir

           If name contains a replacement string and the replaced result ends in /, then output
           files will be stored in the resulting dir.

           E.g.

             parallel --results my_{}/ echo ::: foo bar baz

           will generate the files:

             my_bar/seq
             my_bar/stderr
             my_bar/stdout
             my_baz/seq
             my_baz/stderr
             my_baz/stdout
             my_foo/seq
             my_foo/stderr
             my_foo/stdout

           See also: --output-as-files --tag --header --joblog

       --resume
           Resumes from the last unfinished job.

           By reading --joblog or the --results dir GNU parallel will figure out the last
           unfinished job and continue from there. As GNU parallel only looks at the sequence
           numbers in --joblog then the input, the command, and --joblog all have to remain
           unchanged; otherwise GNU parallel may run wrong commands.

           See also: --joblog --results --resume-failed --retries

       --resume-failed
           Retry all failed and resume from the last unfinished job.

           By reading --joblog GNU parallel will figure out the failed jobs and run those again.
           After that it will resume last unfinished job and continue from there. As GNU parallel
           only looks at the sequence numbers in --joblog then the input, the command, and
           --joblog all have to remain unchanged; otherwise GNU parallel may run wrong commands.

           See also: --joblog --resume --retry-failed --retries

       --retry-failed
           Retry all failed jobs in joblog.

           By reading --joblog GNU parallel will figure out the failed jobs and run those again.

           --retry-failed ignores the command and arguments on the command line: It only looks at
           the joblog.

           Differences between --resume, --resume-failed, --retry-failed

           In this example exit {= $_%=2 =} will cause every other job to fail.

             timeout -k 1 4 parallel --joblog log -j10 \
               'sleep {}; exit {= $_%=2 =}' ::: {10..1}

           4 jobs completed. 2 failed:

             Seq   [...]   Exitval Signal  Command
             10    [...]   1       0       sleep 1; exit 1
             9     [...]   0       0       sleep 2; exit 0
             8     [...]   1       0       sleep 3; exit 1
             7     [...]   0       0       sleep 4; exit 0

           --resume does not care about the Exitval, but only looks at Seq. If the Seq is run, it
           will not be run again. So if needed, you can change the command for the seqs not run
           yet:

             parallel --resume --joblog log -j10 \
               'sleep .{}; exit {= $_%=2 =}' ::: {10..1}

             Seq   [...]   Exitval Signal  Command
             [... as above ...]
             1     [...]   0       0       sleep .10; exit 0
             6     [...]   1       0       sleep .5; exit 1
             5     [...]   0       0       sleep .6; exit 0
             4     [...]   1       0       sleep .7; exit 1
             3     [...]   0       0       sleep .8; exit 0
             2     [...]   1       0       sleep .9; exit 1

           --resume-failed cares about the Exitval, but also only looks at Seq to figure out
           which commands to run. Again this means you can change the command, but not the
           arguments. It will run the failed seqs and the seqs not yet run:

             parallel --resume-failed --joblog log -j10 \
               'echo {};sleep .{}; exit {= $_%=3 =}' ::: {10..1}

             Seq   [...]   Exitval Signal  Command
             [... as above ...]
             10    [...]   1       0       echo 1;sleep .1; exit 1
             8     [...]   0       0       echo 3;sleep .3; exit 0
             6     [...]   2       0       echo 5;sleep .5; exit 2
             4     [...]   1       0       echo 7;sleep .7; exit 1
             2     [...]   0       0       echo 9;sleep .9; exit 0

           --retry-failed cares about the Exitval, but takes the command from the joblog. It
           ignores any arguments or commands given on the command line:

             parallel --retry-failed --joblog log -j10 this part is ignored

             Seq   [...]   Exitval Signal  Command
             [... as above ...]
             10    [...]   1       0       echo 1;sleep .1; exit 1
             6     [...]   2       0       echo 5;sleep .5; exit 2
             4     [...]   1       0       echo 7;sleep .7; exit 1

           See also: --joblog --resume --resume-failed --retries

       --retries n
           Try failing jobs n times.

           If a job fails, retry it on another computer on which it has not failed. Do this n
           times. If there are fewer than n computers in --sshlogin GNU parallel will re-use all
           the computers. This is useful if some jobs fail for no apparent reason (such as
           network failure).

           n=0 means infinite.

           See also: --term-seq --sshlogin

       --return filename
           Transfer files from remote computers.

           --return is used with --sshlogin when the arguments are files on the remote computers.
           When processing is done the file filename will be transferred from the remote computer
           using rsync and will be put relative to the default login dir. E.g.

             echo foo/bar.txt | parallel --return {.}.out \
               --sshlogin server.example.com touch {.}.out

           This will transfer the file $HOME/foo/bar.out from the computer server.example.com to
           the file foo/bar.out after running touch foo/bar.out on server.example.com.

             parallel -S server --trc out/./{}.out touch {}.out ::: in/file

           This will transfer the file in/file.out from the computer server.example.com to the
           files out/in/file.out after running touch in/file.out on server.

             echo /tmp/foo/bar.txt | parallel --return {.}.out \
               --sshlogin server.example.com touch {.}.out

           This will transfer the file /tmp/foo/bar.out from the computer server.example.com to
           the file /tmp/foo/bar.out after running touch /tmp/foo/bar.out on server.example.com.

           Multiple files can be transferred by repeating the option multiple times:

             echo /tmp/foo/bar.txt | parallel \
               --sshlogin server.example.com \
               --return {.}.out --return {.}.out2 touch {.}.out {.}.out2

           --return is ignored when used with --sshlogin : or when not used with --sshlogin.

           For details on transferring see --transferfile.

           See also: --transfer --transferfile --sshlogin --cleanup --workdir

       --round-robin
       --round
           Distribute chunks of standard input in a round robin fashion.

           Normally --pipe will give a single block to each instance of the command. With
           --round-robin all blocks will at random be written to commands already running. This
           is useful if the command takes a long time to initialize.

           With --keep-order and --round-robin the jobslots will get the same blocks as input in
           the same order in every run if the input is kept the same. See details under
           --keep-order.

           --round-robin implies --pipe, except if --pipe-part is given.

           See the section: SPREADING BLOCKS OF DATA.

           See also: --bin --group-by --shard

       --rpl 'tag perl expression'
           Define replacement string.

           Use tag as a replacement string for perl expression. This makes it possible to define
           your own replacement strings. GNU parallel's 7 replacement strings are implemented as:

             --rpl '{} '
             --rpl '{#} 1 $_=$job->seq()'
             --rpl '{%} 1 $_=$job->slot()'
             --rpl '{/} s:.*/::'
             --rpl '{//} $Global::use{"File::Basename"} ||=
                         eval "use File::Basename; 1;"; $_ = dirname($_);'
             --rpl '{/.} s:.*/::; s:\.[^/.]+$::;'
             --rpl '{.} s:\.[^/.]+$::'

           The --plus replacement strings are implemented as:

             --rpl '{+/} s:/[^/]*$:: || s:.*$::'
             --rpl '{+.} s:.*\.:: || s:.*$::'
             --rpl '{+..} s:.*\.([^/.]+\.[^/.]+)$:$1: || s:.*$::'
             --rpl '{+...} s:.*\.([^/.]+\.[^/.]+\.[^/.]+)$:$1: || s:.*$::'
             --rpl '{..} s:\.[^/.]+\.[^/.]+$::'
             --rpl '{...} s:\.[^/.]+\.[^/.]+\.[^/.]+$::'
             --rpl '{/..} s:.*/::; s:\.[^/.]+\.[^/.]+$::'
             --rpl '{/...} s:.*/::; s:\.[^/.]+\.[^/.]+\.[^/.]+$::'
             --rpl '{choose_k}
                    for $t (2..$#arg){ if($arg[$t-1] ge $arg[$t]) { skip() } }'
             --rpl '{##} 1 $_=total_jobs()'
             --rpl '{0%} 1 $f=1+int((log($Global::max_jobs_running||1)/
                                     log(10))); $_=sprintf("%0${f}d",slot())'
             --rpl '{0#} 1 $f=1+int((log(total_jobs())/log(10)));
                         $_=sprintf("%0${f}d",seq())'
             --rpl '{seq(.*?)} $_=eval q{$job->seq()}.qq{$$1}'
             --rpl '{slot(.*?)} $_=eval q{$job->slot()}.qq{$$1}'

             --rpl '{:-([^}]+?)} $_ ||= $$1'
             --rpl '{:(\d+?)} substr($_,0,$$1) = ""'
             --rpl '{:(\d+?):(\d+?)} $_ = substr($_,$$1,$$2);'
             --rpl '{#([^#}][^}]*?)} $nongreedy=::make_regexp_ungreedy($$1);
                                     s/^$nongreedy(.*)/$1/;'
             --rpl '{##([^#}][^}]*?)} s/^$$1//;'
             --rpl '{%([^}]+?)} $nongreedy=::make_regexp_ungreedy($$1);
                                s/(.*)$nongreedy$/$1/;'
             --rpl '{%%([^}]+?)} s/$$1$//;'
             --rpl '{/([^}]+?)/([^}]*?)} s/$$1/$$2/;'
             --rpl '{^([^}]+?)} s/^($$1)/uc($1)/e;'
             --rpl '{^^([^}]+?)} s/($$1)/uc($1)/eg;'
             --rpl '{,([^}]+?)} s/^($$1)/lc($1)/e;'
             --rpl '{,,([^}]+?)} s/($$1)/lc($1)/eg;'

             --rpl '{slot} 1 $_="\${PARALLEL_JOBSLOT}";uq()'
             --rpl '{host} 1 $_="\${PARALLEL_SSHHOST}";uq()'
             --rpl '{sshlogin} 1 $_="\${PARALLEL_SSHLOGIN}";uq()'
             --rpl '{hgrp} 1 $_="\${PARALLEL_HOSTGROUPS}";uq()'
             --rpl '{agrp} 1 $_="\${PARALLEL_ARGHOSTGROUPS}";uq()'

           If the user defined replacement string starts with '{' it can also be used as a
           positional replacement string (like {2.}).

           It is recommended to only change $_ but you have full access to all of GNU parallel's
           internal functions and data structures.

           Here are a few examples:

             Is the job sequence even or odd?
             --rpl '{odd} $_ = seq() % 2 ? "odd" : "even"'
             Pad job sequence with leading zeros to get equal width
             --rpl '{0#} $f=1+int("".(log(total_jobs())/log(10)));
               $_=sprintf("%0${f}d",seq())'
             Job sequence counting from 0
             --rpl '{#0} $_ = seq() - 1'
             Job slot counting from 2
             --rpl '{%1} $_ = slot() + 1'
             Remove all extensions
             --rpl '{:} s:(\.[^/]+)*$::'

           You can have dynamic replacement strings by including parenthesis in the replacement
           string and adding a regular expression between the parenthesis. The matching string
           will be inserted as $$1:

             parallel --rpl '{%(.*?)} s/$$1//' echo {%.tar.gz} ::: my.tar.gz
             parallel --rpl '{:%(.+?)} s:$$1(\.[^/]+)*$::' \
               echo {:%_file} ::: my_file.tar.gz
             parallel -n3 --rpl '{/:%(.*?)} s:.*/(.*)$$1(\.[^/]+)*$:$1:' \
               echo job {#}: {2} {2.} {3/:%_1} ::: a/b.c c/d.e f/g_1.h.i

           You can even use multiple matches:

             parallel --rpl '{/(.+?)/(.*?)} s/$$1/$$2/;'
               echo {/replacethis/withthis} {/b/C} ::: a_replacethis_b

             parallel --rpl '{(.*?)/(.*?)} $_="$$2$_$$1"' \

               echo {swap/these} ::: -middle-
           See also: {=perl expression=} --parens

       --rsync-opts options
           Options to pass on to rsync.

           Setting --rsync-opts takes precedence over setting the environment variable
           $PARALLEL_RSYNC_OPTS.

       --max-chars max-chars
       -s max-chars
           Limit length of command.

           Use at most max-chars characters per command line, including the command and initial-
           arguments and the terminating nulls at the ends of the argument strings.  The largest
           allowed value is system-dependent, and is calculated as the argument length limit for
           exec, less the size of your environment.  The default value is the maximum.

           max-chars can be postfixed with K, M, G, T, P, k, m, g, t, or p (see UNIT PREFIX).

           Implies -X unless -m or --xargs is set.

           See also: -X -m --xargs --max-line-length-allowed --show-limits

       --show-limits
           Display limits given by the operating system.

           Display the limits on the command-line length which are imposed by the operating
           system and the -s option.  Pipe the input from /dev/null (and perhaps specify
           --no-run-if-empty) if you don't want GNU parallel to do anything.

           See also: --max-chars --max-line-length-allowed --version

       --semaphore
           Work as a counting semaphore.

           --semaphore will cause GNU parallel to start command in the background. When the
           number of jobs given by --jobs is reached, GNU parallel will wait for one of these to
           complete before starting another command.

           --semaphore implies --bg unless --fg is specified.

           The command sem is an alias for parallel --semaphore.

           See also: man sem --bg --fg --semaphore-name --semaphore-timeout --wait

       --semaphore-name name
       --id name
           Use name as the name of the semaphore.

           The default is the name of the controlling tty (output from tty).

           The default normally works as expected when used interactively, but when used in a
           script name should be set. $$ or my_task_name are often a good value.

           The semaphore is stored in ~/.parallel/semaphores/

           Implies --semaphore.

           See also: man sem --semaphore

       --semaphore-timeout secs
       --st secs
           If secs > 0: If the semaphore is not released within secs seconds, take it anyway.

           If secs < 0: If the semaphore is not released within secs seconds, exit.

           secs is in seconds, but can be postfixed with s, m, h, or d (see the section TIME
           POSTFIXES).

           Implies --semaphore.

           See also: man sem

       --seqreplace replace-str
           Use the replacement string replace-str instead of {#} for job sequence number.

           See also: {#}

       --session
           Record names in current environment in $PARALLEL_IGNORED_NAMES and exit.

           Only used with env_parallel. Aliases, functions, and variables with names in
           $PARALLEL_IGNORED_NAMES will not be copied.  So you should set variables/function you
           want copied after running --session.

           It is similar to --record-env, but only for this session.

           Only supported in Ash, Bash, Dash, Ksh, Sh, and Zsh.

           See also: --env --record-env env_parallel

       --shard shardexpr
           Use shardexpr as shard key and shard input to the jobs.

           shardexpr is [column number|column name] [perlexpression] e.g.:

             3
             Address
             3 $_%=100
             Address s/\d//g

           Each input line is split using --colsep. The string of the column is put into $_, the
           perl expression is executed, the resulting string is hashed so that all lines of a
           given value is given to the same job slot.

           This is similar to sharding in databases.

           The performance is in the order of 100K rows per second. Faster if the shardcol is
           small (<10), slower if it is big (>100).

           --shard requires --pipe and a fixed numeric value for --jobs.

           See the section: SPREADING BLOCKS OF DATA.

           See also: --bin --group-by --round-robin

       --shebang
       --hashbang
           GNU parallel can be called as a shebang (#!) command as the first line of a script.
           The content of the file will be treated as inputsource.

           Like this:

             #!/usr/bin/parallel --shebang -r wget

             https://ftpmirror.gnu.org/parallel/parallel-20120822.tar.bz2
             https://ftpmirror.gnu.org/parallel/parallel-20130822.tar.bz2
             https://ftpmirror.gnu.org/parallel/parallel-20140822.tar.bz2

           --shebang must be set as the first option.

           On FreeBSD env is needed:

             #!/usr/bin/env -S parallel --shebang -r wget

             https://ftpmirror.gnu.org/parallel/parallel-20120822.tar.bz2
             https://ftpmirror.gnu.org/parallel/parallel-20130822.tar.bz2
             https://ftpmirror.gnu.org/parallel/parallel-20140822.tar.bz2

           There are many limitations of shebang (#!) depending on your operating system. See
           details on https://www.in-ulm.de/~mascheck/various/shebang/

           See also: --shebang-wrap

       --shebang-wrap
           GNU parallel can parallelize scripts by wrapping the shebang line. If the program can
           be run like this:

             cat arguments | parallel the_program

           then the script can be changed to:

             #!/usr/bin/parallel --shebang-wrap /original/parser --options

           E.g.

             #!/usr/bin/parallel --shebang-wrap /usr/bin/python

           If the program can be run like this:

             cat data | parallel --pipe the_program

           then the script can be changed to:

             #!/usr/bin/parallel --shebang-wrap --pipe /orig/parser --opts

           E.g.

             #!/usr/bin/parallel --shebang-wrap --pipe /usr/bin/perl -w

           --shebang-wrap must be set as the first option.

           See also: --shebang

       --shell-completion shell
           Generate shell completion code for interactive shells.

           Supported shells: bash zsh.

           Use auto as shell to automatically detect running shell.

           Activate the completion code with:

             zsh% eval "$(parallel --shell-completion auto)"
             bash$ eval "$(parallel --shell-completion auto)"

           Or put this `/usr/share/zsh/site-functions/_parallel`, then `compinit` to generate
           `~/.zcompdump`:

             #compdef parallel

             (( $+functions[_comp_parallel] )) ||
               eval "$(parallel --shell-completion auto)" &&
               _comp_parallel

       --shell-quote
           Does not run the command but quotes it. Useful for making quoted composed commands for
           GNU parallel.

           Multiple --shell-quote with quote the string multiple times, so parallel --shell-quote
           | parallel --shell-quote can be written as parallel --shell-quote --shell-quote.

           See also: --quote

       --shuf
           Shuffle jobs.

           When having multiple input sources it is hard to randomize jobs. --shuf will generate
           all jobs, and shuffle them before running them. This is useful to get a quick preview
           of the results before running the full batch.

           Combined with --halt soon,done=1% you can run a random 1% sample of all jobs:

             parallel --shuf --halt soon,done=1% echo ::: {1..100} ::: {1..100}

           See also: --halt

       --skip-first-line
           Do not use the first line of input (used by GNU parallel itself when called with
           --shebang).

       --sql DBURL (obsolete)
           Use --sql-master instead.

       --sql-master DBURL
           Submit jobs via SQL server. DBURL must point to a table, which will contain the same
           information as --joblog, the values from the input sources (stored in columns V1 ..
           Vn), and the output (stored in columns Stdout and Stderr).

           If DBURL is prepended with '+' GNU parallel assumes the table is already made with the
           correct columns and appends the jobs to it.

           If DBURL is not prepended with '+' the table will be dropped and created with the
           correct amount of V-columns unless

           --sqlmaster does not run any jobs, but it creates the values for the jobs to be run.
           One or more --sqlworker must be run to actually execute the jobs.

           If --wait is set, GNU parallel will wait for the jobs to complete.

           The format of a DBURL is:

             [sql:]vendor://[[user][:pwd]@][host][:port]/[db]/table

           E.g.

             sql:mysql://hr:hr@localhost:3306/hrdb/jobs
             mysql://scott:tiger@my.example.com/pardb/paralleljobs
             sql:oracle://scott:tiger@ora.example.com/xe/parjob
             postgresql://scott:tiger@pg.example.com/pgdb/parjob
             pg:///parjob
             sqlite3:///%2Ftmp%2Fpardb.sqlite/parjob
             csv:///%2Ftmp%2Fpardb/parjob

           Notice how / in the path of sqlite and CVS must be encoded as %2F. Except the last /
           in CSV which must be a /.

           It can also be an alias from ~/.sql/aliases:

             :myalias mysql:///mydb/paralleljobs

           See also: --sql-and-worker --sql-worker --joblog

       --sql-and-worker DBURL
           Shorthand for: --sql-master DBURL --sql-worker DBURL.

           See also: --sql-master --sql-worker

       --sql-worker DBURL
           Execute jobs via SQL server. Read the input sources variables from the table pointed
           to by DBURL. The command on the command line should be the same as given by
           --sqlmaster.

           If you have more than one --sqlworker jobs may be run more than once.

           If --sqlworker runs on the local machine, the hostname in the SQL table will not be
           ':' but instead the hostname of the machine.

           See also: --sql-master --sql-and-worker

       --ssh sshcommand
           GNU parallel defaults to using ssh for remote access. This can be overridden with
           --ssh. It can also be set on a per server basis with --sshlogin.

           See also: --sshlogin

       --ssh-delay duration
           Delay starting next ssh by duration.

           GNU parallel will not start another ssh for the next duration.

           duration is in seconds, but can be postfixed with s, m, h, or d.

           See also: TIME POSTFIXES --sshlogin --delay

       --sshlogin [@hostgroups/][ncpus/]sshlogin[,[@hostgroups/][ncpus/]sshlogin[,...]]
       --sshlogin @hostgroup
       -S [@hostgroups/][ncpus/]sshlogin[,[@hostgroups/][ncpus/]sshlogin[,...]]
       -S @hostgroup
           Distribute jobs to remote computers.

           The jobs will be run on a list of remote computers.

           If hostgroups is given, the sshlogin will be added to that hostgroup. Multiple
           hostgroups are separated by '+'. The sshlogin will always be added to a hostgroup
           named the same as sshlogin.

           If only the @hostgroup is given, only the sshlogins in that hostgroup will be used.
           Multiple @hostgroup can be given.

           GNU parallel will determine the number of CPUs on the remote computers and run the
           number of jobs as specified by -j.  If the number ncpus is given GNU parallel will use
           this number for number of CPUs on the host. Normally ncpus will not be needed.

           An sshlogin is of the form:

             [sshcommand [options]] [username[:password]@]hostname

           If password is given, sshpass will be used. Otherwise the sshlogin must not require a
           password (ssh-agent and ssh-copy-id may help with that).

           If the hostname is an IPv6 address, the port can be given separated with p or #. If
           the address is enclosed in [] you can also use :.  E.g. ::1p2222 ::1#2222 [::1]:2222

           Ranges of hostnames can be given in [] like this: server[1,3,8-10] (for server1,
           server3, server8, server9, server10) or server[001,003,008-010] (for server001,
           server003, server008, server009, server010). With Bash's brace expansion you can do:
           -S{dev,prod}[001-100] to get -Sdev[001-100] -Sprod[001-100] More [] are allowed:
           server[1-10].cluster[1-5].example.net

           The sshlogin ':' is special, it means 'no ssh' and will therefore run on the local
           computer.

           The sshlogin '..' is special, it read sshlogins from ~/.parallel/sshloginfile or
           $XDG_CONFIG_HOME/parallel/sshloginfile

           The sshlogin '-' is special, too, it read sshlogins from stdin (standard input).

           To specify more sshlogins separate the sshlogins by comma, newline (in the same
           string), or repeat the options multiple times.

           GNU parallel splits on , (comma) so if your sshlogin contains , (comma) you need to
           replace it with \, or ,,

           For examples: see --sshloginfile.

           The remote host must have GNU parallel installed.

           --sshlogin is known to cause problems with -m and -X.

           See also: --basefile --transferfile --return --cleanup --trc --sshloginfile --workdir
           --filter-hosts --ssh

       --sshloginfile filename
       --slf filename
           File with sshlogins. The file consists of sshlogins on separate lines. Empty lines and
           lines starting with '#' are ignored. Example:

             server.example.com
             username@server2.example.com
             8/my-8-cpu-server.example.com
             2/my_other_username@my-dualcore.example.net
             # This server has SSH running on port 2222
             ssh -p 2222 server.example.net
             4/ssh -p 2222 quadserver.example.net
             # Use a different ssh program
             myssh -p 2222 -l myusername hexacpu.example.net
             # Use a different ssh program with default number of CPUs
             //usr/local/bin/myssh -p 2222 -l myusername hexacpu
             # Use a different ssh program with 6 CPUs
             6//usr/local/bin/myssh -p 2222 -l myusername hexacpu
             # Assume 16 CPUs on the local computer
             16/:
             # Put server1 in hostgroup1
             @hostgroup1/server1
             # Put myusername@server2 in hostgroup1+hostgroup2
             @hostgroup1+hostgroup2/myusername@server2
             # Force 4 CPUs and put 'ssh -p 2222 server3' in hostgroup1
             @hostgroup1/4/ssh -p 2222 server3

           When using a different ssh program the last argument must be the hostname.

           Multiple --sshloginfile are allowed.

           GNU parallel will first look for the file in current dir; if that fails it look for
           the file in ~/.parallel.

           The sshloginfile '..' is special, it read sshlogins from ~/.parallel/sshloginfile

           The sshloginfile '.' is special, it read sshlogins from /etc/parallel/sshloginfile

           The sshloginfile '-' is special, too, it read sshlogins from stdin (standard input).

           If the sshloginfile is changed it will be re-read when a job finishes though at most
           once per second. This makes it possible to add and remove hosts while running.

           This can be used to have a daemon that updates the sshloginfile to only contain
           servers that are up:

               cp original.slf tmp2.slf
               while [ 1 ] ; do
                 nice parallel --nonall -j0 -k --slf original.slf \
                   --tag echo | perl 's/\t$//' > tmp.slf
                 if diff tmp.slf tmp2.slf; then
                   mv tmp.slf tmp2.slf
                 fi
                 sleep 10
               done &
               parallel --slf tmp2.slf ...

           See also: --filter-hosts

       --slotreplace replace-str
           Use the replacement string replace-str instead of {%} for job slot number.

           See also: {%}

       --silent
           Silent.

           The job to be run will not be printed. This is the default.  Can be reversed with -v.

           See also: -v

       --template file=repl
       --tmpl file=repl
           Replace replacement strings in file and save it in repl.

           All replacement strings in the contents of file will be replaced. All replacement
           strings in the name repl will be replaced.

           With --cleanup the new file will be removed when the job is done.

           If my.tmpl contains this:

             Xval: {x}
             Yval: {y}
             FixedValue: 9
             # x with 2 decimals
             DecimalX: {=x $_=sprintf("%.2f",$_) =}
             TenX: {=x $_=$_*10 =}
             RandomVal: {=1 $_=rand() =}

           it can be used like this:

             myprog() { echo Using "$@"; cat "$@"; }
             export -f myprog
             parallel --cleanup --header : --tmpl my.tmpl={#}.t myprog {#}.t \
               ::: x 1.234 2.345 3.45678 ::: y 1 2 3

           See also: {} --cleanup

       --tty
           Open terminal tty.

           If GNU parallel is used for starting a program that accesses the tty (such as an
           interactive program) then this option may be needed. It will default to starting only
           one job at a time (i.e. -j1), not buffer the output (i.e. -u), and it will open a tty
           for the job.

           You can of course override -j1 and -u.

           Using --tty unfortunately means that GNU parallel cannot kill the jobs (with
           --timeout, --memfree, or --halt). This is due to GNU parallel giving each child its
           own process group, which is then killed. Process groups are dependant on the tty.

           See also: --ungroup --open-tty

       --tag
           Tag lines with arguments.

           Each output line will be prepended with the arguments and TAB (\t). When combined with
           --onall or --nonall the lines will be prepended with the sshlogin instead.

           --tag is ignored when using -u.

           See also: --tagstring --ctag

       --tagstring str
           Tag lines with a string.

           Each output line will be prepended with str and TAB (\t). str can contain replacement
           strings such as {}.

           --tagstring is ignored when using -u, --onall, and --nonall.

           See also: --tag --ctagstring

       --tee
           Pipe all data to all jobs.

           Used with --pipe/--pipe-part and :::.

             seq 1000 | parallel --pipe --tee -v wc {} ::: -w -l -c

           How many numbers in 1..1000 contain 0..9, and how many bytes do they fill:

             seq 1000 | parallel --pipe --tee --tag \
               'grep {1} | wc {2}' ::: {0..9} ::: -l -c

           How many words contain a..z and how many bytes do they fill?

             parallel -a /usr/share/dict/words --pipe-part --tee --tag \
               'grep {1} | wc {2}' ::: {a..z} ::: -l -c

           See also: ::: --pipe --pipe-part

       --term-seq sequence
           Termination sequence.

           When a job is killed due to --timeout, --memfree, --halt, or abnormal termination of
           GNU parallel, sequence determines how the job is killed. The default is:

               TERM,200,TERM,100,TERM,50,KILL,25

           which sends a TERM signal, waits 200 ms, sends another TERM signal, waits 100 ms,
           sends another TERM signal, waits 50 ms, sends a KILL signal, waits 25 ms, and exits.
           GNU parallel detects if a process dies before the waiting time is up.

           See also: --halt --timeout --memfree

       --total-jobs jobs
       --total jobs
           Provide the total number of jobs for computing ETA which is also used for --bar.

           Without --total-jobs GNU Parallel will read all jobs before starting a job.
           --total-jobs is useful if the input is generated slowly.

           See also: --bar --eta

       --tmpdir dirname
           Directory for temporary files.

           GNU parallel normally buffers output into temporary files in /tmp. By setting --tmpdir
           you can use a different dir for the files. Setting --tmpdir is equivalent to setting
           $TMPDIR.

           See also: --compress $TMPDIR $PARALLEL_REMOTE_TMPDIR

       --tmux (Long beta testing)
           Use tmux for output. Start a tmux session and run each job in a window in that
           session. No other output will be produced.

           See also: --tmuxpane

       --tmuxpane (Long beta testing)
           Use tmux for output but put output into panes in the first window.  Useful if you want
           to monitor the progress of less than 100 concurrent jobs.

           See also: --tmux

       --timeout duration
           Time out for command. If the command runs for longer than duration seconds it will get
           killed as per --term-seq.

           If duration is followed by a % then the timeout will dynamically be computed as a
           percentage of the median average runtime of successful jobs. Only values > 100% will
           make sense.

           duration is in seconds, but can be postfixed with s, m, h, or d.

           See also: TIME POSTFIXES --term-seq --retries

       --verbose
       -t  Print the job to be run on stderr (standard error).

           See also: -v --interactive

       --transfer
           Transfer files to remote computers.

           Shorthand for: --transferfile {}.

           See also: --transferfile.

       --transferfile filename
       --tf filename
           Transfer filename to remote computers.

           --transferfile is used with --sshlogin to transfer files to the remote computers. The
           files will be transferred using rsync and will be put relative to the work dir.

           The filename will normally contain a replacement string.

           If the path contains /./ the remaining path will be relative to the work dir (for
           details: see rsync). If the work dir is /home/user, the transferring will be as
           follows:

             /tmp/foo/bar   => /tmp/foo/bar
             tmp/foo/bar    => /home/user/tmp/foo/bar
             /tmp/./foo/bar => /home/user/foo/bar
             tmp/./foo/bar  => /home/user/foo/bar

           Examples

           This will transfer the file foo/bar.txt to the computer server.example.com to the file
           $HOME/foo/bar.txt before running wc foo/bar.txt on server.example.com:

             echo foo/bar.txt | parallel --transferfile {} \
               --sshlogin server.example.com wc

           This will transfer the file /tmp/foo/bar.txt to the computer server.example.com to the
           file /tmp/foo/bar.txt before running wc /tmp/foo/bar.txt on server.example.com:

             echo /tmp/foo/bar.txt | parallel --transferfile {} \
               --sshlogin server.example.com wc

           This will transfer the file /tmp/foo/bar.txt to the computer server.example.com to the
           file foo/bar.txt before running wc ./foo/bar.txt on server.example.com:

             echo /tmp/./foo/bar.txt | parallel --transferfile {} \
               --sshlogin server.example.com wc {= s:.*/\./:./: =}

           --transferfile is often used with --return and --cleanup. A shorthand for
           --transferfile {} is --transfer.

           --transferfile is ignored when used with --sshlogin : or when not used with
           --sshlogin.

           See also: --workdir --sshlogin --basefile --return --cleanup

       --trc filename
           Transfer, Return, Cleanup. Shorthand for: --transfer --return filename --cleanup

           See also: --transfer --return --cleanup

       --trim <n|l|r|lr|rl>
           Trim white space in input.

           n   No trim. Input is not modified. This is the default.

           l   Left trim. Remove white space from start of input. E.g. " a bc " -> "a bc ".

           r   Right trim. Remove white space from end of input. E.g. " a bc " -> " a bc".

           lr
           rl  Both trim. Remove white space from both start and end of input. E.g. " a bc " ->
               "a bc". This is the default if --colsep is used.

           See also: --no-run-if-empty {} --colsep

       --ungroup
       -u  Ungroup output.

           Output is printed as soon as possible and bypasses GNU parallel internal processing.
           This may cause output from different commands to be mixed thus should only be used if
           you do not care about the output. Compare these:

             seq 4 | parallel -j0 \
               'sleep {};echo -n start{};sleep {};echo {}end'
             seq 4 | parallel -u -j0 \
               'sleep {};echo -n start{};sleep {};echo {}end'

           It also disables --tag. GNU parallel outputs faster with -u. Compare the speeds of
           these:

             parallel seq ::: 300000000 >/dev/null
             parallel -u seq ::: 300000000 >/dev/null
             parallel --line-buffer seq ::: 300000000 >/dev/null

           Can be reversed with --group.

           See also: --line-buffer --group

       --extensionreplace replace-str
       --er replace-str
           Use the replacement string replace-str instead of {.} for input line without
           extension.

           See also: {.}

       --use-sockets-instead-of-threads
           See also: --use-cores-instead-of-threads

       --use-cores-instead-of-threads
       --use-cpus-instead-of-cores (obsolete)
           Determine how GNU parallel counts the number of CPUs.

           GNU parallel uses this number when the number of jobslots (--jobs) is computed
           relative to the number of CPUs (e.g. 100% or +1).

           CPUs can be counted in three different ways:

           sockets The number of filled CPU sockets (i.e. the number of physical chips).

           cores   The number of physical cores (i.e. the number of physical compute cores).

           threads The number of hyperthreaded cores (i.e. the number of virtual cores - with
                   some of them possibly being hyperthreaded)

           Normally the number of CPUs is computed as the number of CPU threads. With
           --use-sockets-instead-of-threads or --use-cores-instead-of-threads you can force it to
           be computed as the number of filled sockets or number of cores instead.

           Most users will not need these options.

           --use-cpus-instead-of-cores is a (misleading) alias for
           --use-sockets-instead-of-threads and is kept for backwards compatibility.

           See also: --number-of-threads --number-of-cores --number-of-sockets

       -v  Verbose.

           Print the job to be run on stdout (standard output). Can be reversed with --silent.

           Use -v -v to print the wrapping ssh command when running remotely.

           See also: -t

       --version
       -V  Print the version GNU parallel and exit.

       --workdir mydir
       --wd mydir
           Jobs will be run in the dir mydir. The default is the current dir for the local
           machine, and the login dir for remote computers.

           Files transferred using --transferfile and --return will be relative to mydir on
           remote computers.

           The special mydir value ... will create working dirs under ~/.parallel/tmp/. If
           --cleanup is given these dirs will be removed.

           The special mydir value . uses the current working dir.  If the current working dir is
           beneath your home dir, the value . is treated as the relative path to your home dir.
           This means that if your home dir is different on remote computers (e.g. if your login
           is different) the relative path will still be relative to your home dir.

           To see the difference try:

             parallel -S server pwd ::: ""
             parallel --wd . -S server pwd ::: ""
             parallel --wd ... -S server pwd ::: ""

           mydir can contain GNU parallel's replacement strings.

       --wait
           Wait for all commands to complete.

           Used with --semaphore or --sqlmaster.

           See also: man sem

       -X  Multiple arguments with context replace. Insert as many arguments as the command line
           length permits. If multiple jobs are being run in parallel: distribute the arguments
           evenly among the jobs. Use -j1 to avoid this.

           If {} is not used the arguments will be appended to the line.  If {} is used as part
           of a word (like pic{}.jpg) then the whole word will be repeated. If {} is used
           multiple times each {} will be replaced with the arguments.

           Normally -X will do the right thing, whereas -m can give unexpected results if {} is
           used as part of a word.

           Support for -X with --sshlogin is limited and may fail.

           See also: -m

       --exit
       -x  Exit if the size (see the -s option) is exceeded.

       --xargs
           Multiple arguments. Insert as many arguments as the command line length permits.

           If {} is not used the arguments will be appended to the line.  If {} is used multiple
           times each {} will be replaced with all the arguments.

           Support for --xargs with --sshlogin is limited and may fail.

           See also: -X

EXAMPLES

       See: man parallel_examples

SPREADING BLOCKS OF DATA

       --round-robin, --pipe-part, --shard, --bin and --group-by are all specialized versions of
       --pipe.

       In the following n is the number of jobslots given by --jobs. A record starts with
       --recstart and ends with --recend. It is typically a full line. A chunk is a number of
       full records that is approximately the size of a block. A block can contain half records,
       a chunk cannot.

       --pipe starts one job per chunk. It reads blocks from stdin (standard input). It finds a
       record end near a block border and passes a chunk to the program.

       --pipe-part starts one job per chunk - just like normal --pipe. It first finds record
       endings near all block borders in the file and then starts the jobs. By using --block -1
       it will set the block size to size-of-file/n. Used this way it will start n jobs in total.

       --round-robin starts n jobs in total. It reads a block and passes a chunk to whichever job
       is ready to read. It does not parse the content except for identifying where a record ends
       to make sure it only passes full records.

       --shard starts n jobs in total. It parses each line to read the string in the given
       column. Based on this string the line is passed to one of the n jobs. All lines having
       this string will be given to the same jobslot.

       --bin works like --shard but the value of the column must be numeric and is the jobslot
       number it will be passed to. If the value is bigger than n, then n will be subtracted from
       the value until the value is smaller than or equal to n.

       --group-by starts one job per chunk. Record borders are not given by --recend/--recstart.
       Instead a record is defined by a group of lines having the same string in a given column.
       So the string of a given column changes at a chunk border. With --pipe every line is
       parsed, with --pipe-part only a few lines are parsed to find the chunk border.

       --group-by can be combined with --round-robin or --pipe-part.

TIME POSTFIXES

       Arguments that give a duration are given in seconds, but can be expressed as floats
       postfixed with s, m, h, or d which would multiply the float by 1, 60, 60*60, or 60*60*24.
       Thus these are equivalent: 100000 and 1d3.5h16.6m4s.

UNIT PREFIX

       Many numerical arguments in GNU parallel can be postfixed with K, M, G, T, P, k, m, g, t,
       or p which would multiply the number with 1024, 1048576, 1073741824, 1099511627776,
       1125899906842624, 1000, 1000000, 1000000000, 1000000000000, or 1000000000000000,
       respectively.

       You can even give it as a math expression. E.g. 1000000 can be written as 1M-12*2.024*2k.

QUOTING

       GNU parallel is very liberal in quoting. You only need to quote characters that have
       special meaning in shell:

         ( ) $ ` ' " < > ; | \

       and depending on context these needs to be quoted, too:

         ~ & # ! ? space * {

       Therefore most people will never need more quoting than putting '\' in front of the
       special characters.

       Often you can simply put \' around every ':

         perl -ne '/^\S+\s+\S+$/ and print $ARGV,"\n"' file

       can be quoted:

         parallel perl -ne \''/^\S+\s+\S+$/ and print $ARGV,"\n"'\' ::: file

       However, when you want to use a shell variable you need to quote the $-sign. Here is an
       example using $PARALLEL_SEQ. This variable is set by GNU parallel itself, so the
       evaluation of the $ must be done by the sub shell started by GNU parallel:

         seq 10 | parallel -N2 echo seq:\$PARALLEL_SEQ arg1:{1} arg2:{2}

       If the variable is set before GNU parallel starts you can do this:

         VAR=this_is_set_before_starting
         echo test | parallel echo {} $VAR

       Prints: test this_is_set_before_starting

       It is a little more tricky if the variable contains more than one space in a row:

         VAR="two  spaces  between  each  word"
         echo test | parallel echo {} \'"$VAR"\'

       Prints: test two  spaces  between  each  word

       If the variable should not be evaluated by the shell starting GNU parallel but be
       evaluated by the sub shell started by GNU parallel, then you need to quote it:

         echo test | parallel VAR=this_is_set_after_starting \; echo {} \$VAR

       Prints: test this_is_set_after_starting

       It is a little more tricky if the variable contains space:

         echo test |\
           parallel VAR='"two  spaces  between  each  word"' echo {} \'"$VAR"\'

       Prints: test two  spaces  between  each  word

       $$ is the shell variable containing the process id of the shell. This will print the
       process id of the shell running GNU parallel:

         seq 10 | parallel echo $$

       And this will print the process ids of the sub shells started by GNU parallel.

         seq 10 | parallel echo \$\$

       If the special characters should not be evaluated by the sub shell then you need to
       protect it against evaluation from both the shell starting GNU parallel and the sub shell:

         echo test | parallel echo {} \\\$VAR

       Prints: test $VAR

       GNU parallel can protect against evaluation by the sub shell by using -q:

         echo test | parallel -q echo {} \$VAR

       Prints: test $VAR

       This is particularly useful if you have lots of quoting. If you want to run a perl script
       like this:

         perl -ne '/^\S+\s+\S+$/ and print $ARGV,"\n"' file

       It needs to be quoted like one of these:

         ls | parallel perl -ne '/^\\S+\\s+\\S+\$/\ and\ print\ \$ARGV,\"\\n\"'
         ls | parallel perl -ne \''/^\S+\s+\S+$/ and print $ARGV,"\n"'\'

       Notice how spaces, \'s, "'s, and $'s need to be quoted. GNU parallel can do the quoting by
       using option -q:

         ls | parallel -q  perl -ne '/^\S+\s+\S+$/ and print $ARGV,"\n"'

       However, this means you cannot make the sub shell interpret special characters. For
       example because of -q this WILL NOT WORK:

         ls *.gz | parallel -q "zcat {} >{.}"
         ls *.gz | parallel -q "zcat {} | bzip2 >{.}.bz2"

       because > and | need to be interpreted by the sub shell.

       If you get errors like:

         sh: -c: line 0: syntax error near unexpected token
         sh: Syntax error: Unterminated quoted string
         sh: -c: line 0: unexpected EOF while looking for matching `''
         sh: -c: line 1: syntax error: unexpected end of file
         zsh:1: no matches found:

       then you might try using -q.

       If you are using bash process substitution like <(cat foo) then you may try -q and
       prepending command with bash -c:

         ls | parallel -q bash -c 'wc -c <(echo {})'

       Or for substituting output:

         ls | parallel -q bash -c \
           'tar c {} | tee >(gzip >{}.tar.gz) | bzip2 >{}.tar.bz2'

       Conclusion: If this is confusing consider avoiding having to deal with quoting by writing
       a small script or a function (remember to export -f the function) and have GNU parallel
       call that.

LIST RUNNING JOBS

       If you want a list of the jobs currently running you can run:

         killall -USR1 parallel

       GNU parallel will then print the currently running jobs on stderr (standard error).

COMPLETE RUNNING JOBS BUT DO NOT START NEW JOBS

       If you regret starting a lot of jobs you can simply break GNU parallel, but if you want to
       make sure you do not have half-completed jobs you should send the signal SIGHUP to GNU
       parallel:

         killall -HUP parallel

       This will tell GNU parallel to not start any new jobs, but wait until the currently
       running jobs are finished before exiting.

ENVIRONMENT VARIABLES

       $PARALLEL_HOME
                Dir where GNU parallel stores config files, semaphores, and caches information
                between invocations. If set to a non-existent dir, the dir will be created.

                Default: $HOME/.parallel.

       $PARALLEL_ARGHOSTGROUPS
                When using --hostgroups GNU parallel sets this to the hostgroups of the job.

                Remember to quote the $, so it gets evaluated by the correct shell. Or use --plus
                and {agrp}.

       $PARALLEL_HOSTGROUPS
                When using --hostgroups GNU parallel sets this to the hostgroups of the sshlogin
                that the job is run on.

                Remember to quote the $, so it gets evaluated by the correct shell. Or use --plus
                and {hgrp}.

       $PARALLEL_JOBSLOT
                Set by GNU parallel and can be used in jobs run by GNU parallel.  Remember to
                quote the $, so it gets evaluated by the correct shell. Or use --plus and {slot}.

                $PARALLEL_JOBSLOT is the jobslot of the job. It is equal to {%} unless the job is
                being retried. See {%} for details.

       $PARALLEL_PID
                Set by GNU parallel and can be used in jobs run by GNU parallel.  Remember to
                quote the $, so it gets evaluated by the correct shell.

                This makes it possible for the jobs to communicate directly to GNU parallel.

                Example: If each of the jobs tests a solution and one of jobs finds the solution
                the job can tell GNU parallel not to start more jobs by: kill -HUP $PARALLEL_PID.
                This only works on the local computer.

       $PARALLEL_RSYNC_OPTS
                Options to pass on to rsync. Defaults to: -rlDzR.

       $PARALLEL_SHELL
                Use this shell for the commands run by GNU parallel:

                • $PARALLEL_SHELL. If undefined use:

                • The shell that started GNU parallel. If that cannot be determined:

                • $SHELL. If undefined use:

                • /bin/sh

       $PARALLEL_SSH
                GNU parallel defaults to using the ssh command for remote access. This can be
                overridden with $PARALLEL_SSH, which again can be overridden with --ssh. It can
                also be set on a per server basis (see --sshlogin).

       $PARALLEL_SSHHOST
                Set by GNU parallel and can be used in jobs run by GNU parallel.  Remember to
                quote the $, so it gets evaluated by the correct shell. Or use --plus and {host}.

                $PARALLEL_SSHHOST is the host part of an sshlogin line. E.g.

                  4//usr/bin/specialssh user@host

                becomes:

                  host

       $PARALLEL_SSHLOGIN
                Set by GNU parallel and can be used in jobs run by GNU parallel.  Remember to
                quote the $, so it gets evaluated by the correct shell. Or use --plus and
                {sshlogin}.

                The value is the sshlogin line with number of threads removed. E.g.

                  4//usr/bin/specialssh user@host

                becomes:

                  /usr/bin/specialssh user@host

       $PARALLEL_SEQ
                Set by GNU parallel and can be used in jobs run by GNU parallel.  Remember to
                quote the $, so it gets evaluated by the correct shell.

                $PARALLEL_SEQ is the sequence number of the job running.

                Example:

                  seq 10 | parallel -N2 \
                    echo seq:'$'PARALLEL_SEQ arg1:{1} arg2:{2}

                {#} is a shorthand for $PARALLEL_SEQ.

       $PARALLEL_TMUX
                Path to tmux. If unset the tmux in $PATH is used.

       $TMPDIR  Directory for temporary files.

                See also: --tmpdir

       $PARALLEL_REMOTE_TMPDIR
                Directory for temporary files on remote servers.

                See also: --tmpdir

       $PARALLEL
                The environment variable $PARALLEL will be used as default options for GNU
                parallel. If the variable contains special shell characters (e.g. $, *, or space)
                then these need to be to be escaped with \.

                Example:

                  cat list | parallel -j1 -k -v ls
                  cat list | parallel -j1 -k -v -S"myssh user@server" ls

                can be written as:

                  cat list | PARALLEL="-kvj1" parallel ls
                  cat list | PARALLEL='-kvj1 -S myssh\ user@server' \
                    parallel echo

                Notice the \ after 'myssh' is needed because 'myssh' and 'user@server' must be
                one argument.

                See also: --profile

DEFAULT PROFILE (CONFIG FILE)

       The global configuration file /etc/parallel/config, followed by user configuration file
       ~/.parallel/config (formerly known as .parallelrc) will be read in turn if they exist.
       Lines starting with '#' will be ignored. The format can follow that of the environment
       variable $PARALLEL, but it is often easier to simply put each option on its own line.

       Options on the command line take precedence, followed by the environment variable
       $PARALLEL, user configuration file ~/.parallel/config, and finally the global
       configuration file /etc/parallel/config.

       Note that no file that is read for options, nor the environment variable $PARALLEL, may
       contain retired options such as --tollef.

PROFILE FILES

       If --profile set, GNU parallel will read the profile from that file rather than the global
       or user configuration files. You can have multiple --profiles.

       Profiles are searched for in ~/.parallel. If the name starts with / it is seen as an
       absolute path. If the name starts with ./ it is seen as a relative path from current dir.

       Example: Profile for running a command on every sshlogin in ~/.ssh/sshlogins and prepend
       the output with the sshlogin:

         echo --tag -S .. --nonall > ~/.parallel/nonall_profile
         parallel -J nonall_profile uptime

       Example: Profile for running every command with -j-1 and nice

         echo -j-1 nice > ~/.parallel/nice_profile
         parallel -J nice_profile bzip2 -9 ::: *

       Example: Profile for running a perl script before every command:

         echo "perl -e '\$a=\$\$; print \$a,\" \",'\$PARALLEL_SEQ',\" \";';" \
           > ~/.parallel/pre_perl
         parallel -J pre_perl echo ::: *

       Note how the $ and " need to be quoted using \.

       Example: Profile for running distributed jobs with nice on the remote computers:

         echo -S .. nice > ~/.parallel/dist
         parallel -J dist --trc {.}.bz2 bzip2 -9 ::: *

EXIT STATUS

       Exit status depends on --halt-on-error if one of these is used: success=X, success=Y%,
       fail=Y%.

       0     All jobs ran without error. If success=X is used: X jobs ran without error. If
             success=Y% is used: Y% of the jobs ran without error.

       1-100 Some of the jobs failed. The exit status gives the number of failed jobs. If Y% is
             used the exit status is the percentage of jobs that failed.

       101   More than 100 jobs failed.

       255   Other error.

       -1 (In joblog and SQL table)
             Killed by Ctrl-C, timeout, not enough memory or similar.

       -2 (In joblog and SQL table)
             skip() was called in {= =}.

       -1000 (In SQL table)
             Job is ready to run (set by --sqlmaster).

       -1220 (In SQL table)
             Job is taken by worker (set by --sqlworker).

       If fail=1 is used, the exit status will be the exit status of the failing job.

DIFFERENCES BETWEEN GNU Parallel AND ALTERNATIVES

       See: man parallel_alternatives

BUGS

   Quoting of newline
       Because of the way newline is quoted this will not work:

         echo 1,2,3 | parallel -vkd, "echo 'a{}b'"

       However, these will all work:

         echo 1,2,3 | parallel -vkd, echo a{}b
         echo 1,2,3 | parallel -vkd, "echo 'a'{}'b'"
         echo 1,2,3 | parallel -vkd, "echo 'a'"{}"'b'"

   Speed
       Startup

       GNU parallel is slow at starting up - around 250 ms the first time and 150 ms after that.

       Job startup

       Starting a job on the local machine takes around 3-10 ms. This can be a big overhead if
       the job takes very few ms to run. Often you can group small jobs together using -X which
       will make the overhead less significant. Or you can run multiple GNU parallels as
       described in EXAMPLE: Speeding up fast jobs.

       SSH

       When using multiple computers GNU parallel opens ssh connections to them to figure out how
       many connections can be used reliably simultaneously (Namely SSHD's MaxStartups). This
       test is done for each host in serial, so if your --sshloginfile contains many hosts it may
       be slow.

       If your jobs are short you may see that there are fewer jobs running on the remote systems
       than expected. This is due to time spent logging in and out. -M may help here.

       Disk access

       A single disk can normally read data faster if it reads one file at a time instead of
       reading a lot of files in parallel, as this will avoid disk seeks. However, newer disk
       systems with multiple drives can read faster if reading from multiple files in parallel.

       If the jobs are of the form read-all-compute-all-write-all, so everything is read before
       anything is written, it may be faster to force only one disk access at the time:

         sem --id diskio cat file | compute | sem --id diskio cat > file

       If the jobs are of the form read-compute-write, so writing starts before all reading is
       done, it may be faster to force only one reader and writer at the time:

         sem --id read cat file | compute | sem --id write cat > file

       If the jobs are of the form read-compute-read-compute, it may be faster to run more jobs
       in parallel than the system has CPUs, as some of the jobs will be stuck waiting for disk
       access.

   --nice limits command length
       The current implementation of --nice is too pessimistic in the max allowed command length.
       It only uses a little more than half of what it could. This affects -X and -m. If this
       becomes a real problem for you, file a bug-report.

   Aliases and functions do not work
       If you get:

         Can't exec "command": No such file or directory

       or:

         open3: exec of by command failed

       or:

         /bin/bash: command: command not found

       it may be because command is not known, but it could also be because command is an alias
       or a function. If it is a function you need to export -f the function first or use
       env_parallel. An alias will only work if you use env_parallel.

   Database with MySQL fails randomly
       The --sql* options may fail randomly with MySQL. This problem does not exist with
       PostgreSQL.

REPORTING BUGS

       Report bugs to <parallel@gnu.org> or
       https://savannah.gnu.org/bugs/?func=additem&group=parallel

       When you write your report, please keep in mind, that you must give the reader enough
       information to be able to run exactly what you run. So you need to include all data and
       programs that you use to show the problem.

       See a perfect bug report on
       https://lists.gnu.org/archive/html/bug-parallel/2015-01/msg00000.html

       Your bug report should always include:

       • The error message you get (if any). If the error message is not from GNU parallel you
         need to show why you think GNU parallel caused this.

       • The complete output of parallel --version. If you are not running the latest released
         version (see https://ftp.gnu.org/gnu/parallel/) you should specify why you believe the
         problem is not fixed in that version.

       • A minimal, complete, and verifiable example (See description on
         https://stackoverflow.com/help/mcve).

         It should be a complete example that others can run which shows the problem including
         all files needed to run the example. This should preferably be small and simple, so try
         to remove as many options as possible.

         A combination of yes, seq, cat, echo, wc, and sleep can reproduce most errors.

         If your example requires large files, see if you can make them with something like seq
         100000000 > bigfile or yes | head -n 1000000000 > file. If you need multiple columns:
         paste <(seq 1000) <(seq 1000 1999)

         If your example requires remote execution, see if you can use localhost - maybe using
         another login.

         If you have access to a different system (maybe a VirtualBox on your own machine), test
         if your MCVE shows the problem on that system. If it does not, read below.

       • The output of your example. If your problem is not easily reproduced by others, the
         output might help them figure out the problem.

       • Whether you have watched the intro videos
         (https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1), walked through the tutorial
         (man parallel_tutorial), and read the examples (man parallel_examples).

   Bug dependent on environment
       If you suspect the error is dependent on your environment or distribution, please see if
       you can reproduce the error on one of these VirtualBox images:
       https://sourceforge.net/projects/virtualboximage/files/
       https://www.osboxes.org/virtualbox-images/

       Specifying the name of your distribution is not enough as you may have installed software
       that is not in the VirtualBox images.

       If you cannot reproduce the error on any of the VirtualBox images above, see if you can
       build a VirtualBox image on which you can reproduce the error. If not you should assume
       the debugging will be done through you. That will put a lot more burden on you and it is
       extra important you give any information that help. In general the problem will be fixed
       faster and with much less work for you if you can reproduce the error on a VirtualBox -
       even if you have to build a VirtualBox image.

   In summary
       Your report must include:

       • parallel --version

       • output + error message

       • full example including all files

       • VirtualBox image, if you cannot reproduce it on other systems

AUTHOR

       When using GNU parallel for a publication please cite:

       O. Tange (2011): GNU Parallel - The Command-Line Power Tool, ;login: The USENIX Magazine,
       February 2011:42-47.

       Copyright (C) 2007-10-18 Ole Tange, http://ole.tange.dk

       Copyright (C) 2008-2010 Ole Tange, http://ole.tange.dk

       Copyright (C) 2010-2024 Ole Tange, http://ole.tange.dk and Free Software Foundation, Inc.

       Parts of the manual concerning xargs compatibility is inspired by the manual of xargs from
       GNU findutils 4.4.2.

LICENSE

       This program is free software; you can redistribute it and/or modify it under the terms of
       the GNU General Public License as published by the Free Software Foundation; either
       version 3 of the License, or at your option any later version.

       This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
       without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
       See the GNU General Public License for more details.

       You should have received a copy of the GNU General Public License along with this program.
       If not, see <https://www.gnu.org/licenses/>.

   Documentation license I
       Permission is granted to copy, distribute and/or modify this documentation under the terms
       of the GNU Free Documentation License, Version 1.3 or any later version published by the
       Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with
       no Back-Cover Texts.  A copy of the license is included in the file
       LICENSES/GFDL-1.3-or-later.txt.

   Documentation license II
       You are free:

       to Share to copy, distribute and transmit the work

       to Remix to adapt the work

       Under the following conditions:

       Attribution
                You must attribute the work in the manner specified by the author or licensor
                (but not in any way that suggests that they endorse you or your use of the work).

       Share Alike
                If you alter, transform, or build upon this work, you may distribute the
                resulting work only under the same, similar or a compatible license.

       With the understanding that:

       Waiver   Any of the above conditions can be waived if you get permission from the
                copyright holder.

       Public Domain
                Where the work or any of its elements is in the public domain under applicable
                law, that status is in no way affected by the license.

       Other Rights
                In no way are any of the following rights affected by the license:

                • Your fair dealing or fair use rights, or other applicable copyright exceptions
                  and limitations;

                • The author's moral rights;

                • Rights other persons may have either in the work itself or in how the work is
                  used, such as publicity or privacy rights.

       Notice   For any reuse or distribution, you must make clear to others the license terms of
                this work.

       A copy of the full license is included in the file as LICENCES/CC-BY-SA-4.0.txt

DEPENDENCIES

       GNU parallel uses Perl, and the Perl modules Getopt::Long, IPC::Open3, Symbol, IO::File,
       POSIX, and File::Temp.

       For --csv it uses the Perl module Text::CSV.

       For remote usage it uses rsync with ssh.

SEE ALSO

       parallel_tutorial(1), env_parallel(1), parset(1), parsort(1), parallel_alternatives(1),
       parallel_design(7), niceload(1), sql(1), ssh(1), ssh-agent(1), sshpass(1), ssh-copy-id(1),
       rsync(1)