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       sort - sort, merge, or sequence check text files


       sort [-m][-o output][-bdfinru][-t char][-k keydef]... [file...]

       sort -c [-bdfinru][-t char][-k keydef][file]


       The sort utility shall perform one of the following functions:

        1. Sort  lines  of  all  the  named  files together and write the result to the specified

        2. Merge lines of all the named (presorted) files together and write the  result  to  the
           specified output.

        3. Check that a single input file is correctly presorted.

       Comparisons shall be based on one or more sort keys extracted from each line of input (or,
       if no sort keys are specified, the entire line up to, but not including,  the  terminating
       <newline>), and shall be performed using the collating sequence of the current locale.


       The  sort  utility  shall  conform to the Base Definitions volume of IEEE Std 1003.1-2001,
       Section 12.2, Utility Syntax Guidelines, and the -k keydef option should  follow  the  -b,
       -d, -f, -i, -n, and -r options.

       The following options shall be supported:

       -c     Check  that  the single input file is ordered as specified by the arguments and the
              collating sequence of the current locale. No output shall  be  produced;  only  the
              exit code shall be affected.

       -m     Merge only; the input file shall be assumed to be already sorted.

       -o  output
              Specify  the name of an output file to be used instead of the standard output. This
              file can be the same as one of the input files.

       -u     Unique: suppress all but one in each set of lines having equal keys.  If used  with
              the  -c  option,  check that there are no lines with duplicate keys, in addition to
              checking that the input file is sorted.

       The following options shall override the default ordering  rules.  When  ordering  options
       appear  independent  of  any  key field specifications, the requested field ordering rules
       shall be applied globally to all sort keys. When attached to a specific key (see -k),  the
       specified ordering options shall override all global ordering options for that key.

       -d     Specify  that  only  <blank>s and alphanumeric characters, according to the current
              setting of LC_CTYPE  ,  shall  be  significant  in  comparisons.  The  behavior  is
              undefined for a sort key to which -i or -n also applies.

       -f     Consider all lowercase characters that have uppercase equivalents, according to the
              current setting of LC_CTYPE , to be the uppercase equivalent for  the  purposes  of

       -i     Ignore  all  characters that are non-printable, according to the current setting of
              LC_CTYPE .

       -n     Restrict the sort  key  to  an  initial  numeric  string,  consisting  of  optional
              <blank>s,  optional  minus  sign,  and  zero  or more digits with an optional radix
              character and thousands separators (as defined in the current locale), which  shall
              be  sorted  by  arithmetic  value.  An empty digit string shall be treated as zero.
              Leading zeros and signs on zeros shall not affect ordering.

       -r     Reverse the sense of comparisons.

       The treatment of field separators can be altered using the options:

       -b     Ignore leading <blank>s when determining the starting and  ending  positions  of  a
              restricted  sort  key. If the -b option is specified before the first -k option, it
              shall be applied to all -k options.  Otherwise,  the  -b  option  can  be  attached
              independently to each -k field_start or field_end option-argument (see below).

       -t  char
              Use  char as the field separator character; char shall not be considered to be part
              of a field (although it can be included in a sort key).  Each  occurrence  of  char
              shall  be significant (for example, <char><char> delimits an empty field). If -t is
              not specified, <blank>s shall be used as default  field  separators;  each  maximal
              non-empty  sequence  of  <blank>s  that  follows  a  non-  <blank> shall be a field

       Sort keys can be specified using the options:

       -k  keydef
              The keydef argument is a restricted sort key field definition.  The format of  this
              definition is:


       where  field_start  and  field_end  define a key field restricted to a portion of the line
       (see the EXTENDED DESCRIPTION section), and type is a modifier from the list of characters
       'b'  , 'd' , 'f' , 'i' , 'n' , 'r' . The 'b' modifier shall behave like the -b option, but
       shall apply only to the field_start or field_end to  which  it  is  attached.   The  other
       modifiers  shall  behave  like  the corresponding options, but shall apply only to the key
       field to which  they  are  attached;  they  shall  have  this  effect  if  specified  with
       field_start,  field_end,  or  both.  If  any modifier is attached to a field_start or to a
       field_end, no option shall apply to either. Implementations shall support  at  least  nine
       occurrences  of  the -k option, which shall be significant in command line order. If no -k
       option is specified, a default sort key of the entire line shall be used.

       When there are multiple key fields, later keys shall be compared only  after  all  earlier
       keys  compare  equal. Except when the -u option is specified, lines that otherwise compare
       equal shall be ordered as if none of the options -d, -f, -i, -n, or -k were  present  (but
       with  -r still in effect, if it was specified) and with all bytes in the lines significant
       to the comparison. The order in which lines  that  still  compare  equal  are  written  is


       The following operand shall be supported:

       file   A  pathname  of  a  file  to be sorted, merged, or checked. If no file operands are
              specified, or if a file operand is '-' , the standard input shall be used.


       The standard input shall be used only if no file operands are  specified,  or  if  a  file
       operand is '-' .  See the INPUT FILES section.


       The input files shall be text files, except that the sort utility shall add a <newline> to
       the end of a file ending with an incomplete last line.


       The following environment variables shall affect the execution of sort:

       LANG   Provide a default value for the internationalization variables that  are  unset  or
              null.  (See  the  Base  Definitions  volume  of  IEEE Std 1003.1-2001, Section 8.2,
              Internationalization Variables for the precedence of internationalization variables
              used to determine the values of locale categories.)

       LC_ALL If  set  to  a  non-empty  string  value,  override  the  values  of  all the other
              internationalization variables.


              Determine the locale for ordering rules.

              Determine the locale for the interpretation of sequences of bytes of text  data  as
              characters  (for  example,  single-byte  as  opposed  to  multi-byte  characters in
              arguments and input files) and the behavior of character classification for the -b,
              -d, -f, -i, and -n options.

              Determine  the  locale  that  should  be  used to affect the format and contents of
              diagnostic messages written to standard error.


              Determine the locale for the  definition  of  the  radix  character  and  thousands
              separator for the -n option.

              Determine the location of message catalogs for the processing of LC_MESSAGES .




       Unless  the  -o  or -c options are in effect, the standard output shall contain the sorted


       The standard error shall  be  used  for  diagnostic  messages.  A  warning  message  about
       correcting  an incomplete last line of an input file may be generated, but need not affect
       the final exit status.


       If the -o option is in effect, the sorted input shall be written to the file output.


       The notation:

              -k field_start[type][,field_end[type]]

       shall define a key field that begins at  field_start  and  ends  at  field_end  inclusive,
       unless  field_start falls beyond the end of the line or after field_end, in which case the
       key field is empty. A missing field_end shall mean the last character of the line.

       A field comprises a maximal sequence of non-separating characters and, in the  absence  of
       option -t, any preceding field separator.

       The field_start portion of the keydef option-argument shall have the form:


       Fields  and  characters  within fields shall be numbered starting with 1. The field_number
       and first_character pieces, interpreted as positive decimal integers,  shall  specify  the
       first character to be used as part of a sort key. If .first_character is omitted, it shall
       refer to the first character of the field.

       The field_end portion of the keydef option-argument shall have the form:


       The field_number shall be as described above for field_start.  The  last_character  piece,
       interpreted as a non-negative decimal integer, shall specify the last character to be used
       as part of the sort key.  If  last_character  evaluates  to  zero  or  .last_character  is
       omitted, it shall refer to the last character of the field specified by field_number.

       If  the  -b  option  or  b  type modifier is in effect, characters within a field shall be
       counted from the first non-  <blank>  in  the  field.  (This  shall  apply  separately  to
       first_character and last_character.)


       The following exit values shall be returned:

        0     All  input  files  were output successfully, or -c was specified and the input file
              was correctly sorted.

        1     Under the -c option, the file was not ordered as specified, or if  the  -c  and  -u
              options were both specified, two input lines were found with equal keys.

       >1     An error occurred.



       The following sections are informative.


       The  default  value  for  -t,  <blank>,  has  different  properties  from, for example, -t
       "<space>". If a line contains:


       the following treatment would occur with default separation  as  opposed  to  specifically
       selecting a <space>:

                                Field   Default             -t "<space>"
                                1       <space><space>foo   empty
                                2       empty               empty
                                3       empty               foo

       The  leading  field  separator  itself  is  included  in  a field when -t is not used. For
       example, this command returns an exit status  of  zero,  meaning  the  input  was  already

              sort -c -k 2 <<eof

       (assuming  that a <tab> precedes the <space> in the current collating sequence). The field
       separator is not included in a field when it is explicitly set via -t. This is  historical
       practice and allows usage such as:

              sort -t "|" -k 2n <<eof
              Columbia|100385|South Carolina

       where  the  second  field  can  be correctly sorted numerically without regard to the non-
       numeric field separator.

       The wording in the OPTIONS section clarifies that the -b, -d, -f, -i, -n, and  -r  options
       have  to  come  before  the  first sort key specified if they are intended to apply to all
       specified keys. The way it is described in this  volume  of  IEEE Std 1003.1-2001  matches
       historical  practice,  not  historical documentation. The results are unspecified if these
       options are specified after a -k option.

       The -f option might not work as expected in  locales  where  there  is  not  a  one-to-one
       mapping between an uppercase and a lowercase letter.


        1. The  following  command sorts the contents of infile with the second field as the sort

           sort -k 2,2 infile

        2. The following command sorts, in reverse order, the contents of  infile1  and  infile2,
           placing  the  output  in outfile and using the second character of the second field as
           the sort key (assuming that the first character of  the  second  field  is  the  field

           sort -r -o outfile -k 2.2,2.2 infile1 infile2

        3. The  following command sorts the contents of infile1 and infile2 using the second non-
           <blank> of the second field as the sort key:

           sort -k 2.2b,2.2b infile1 infile2

        4. The following command prints the System V password file (user database) sorted by  the
           numeric user ID (the third colon-separated field):

           sort -t : -k 3,3n /etc/passwd

        5. The  following command prints the lines of the already sorted file infile, suppressing
           all but one occurrence of lines having the same third field:

           sort -um -k 3.1,3.0 infile


       Examples in some historical documentation state that options -um with one input file  keep
       the  first  in  each  set  of  lines  with  equal  keys. This behavior was deemed to be an
       implementation artifact and was not standardized.

       The -z option was omitted; it is not standard practice on most systems and is inconsistent
       with  using sort to sort several files individually and then merge them together. The text
       concerning -z in historical documentation appeared to require implementations to determine
       the proper buffer length during the sort phase of operation, but not during the merge.

       The  -y option was omitted because of non-portability. The -M option, present in System V,
       was omitted because of non-portability in international usage.

       An undocumented -T option exists  in  some  implementations.  It  is  used  to  specify  a
       directory  for  intermediate  files.  Implementations are encouraged to support the use of
       the TMPDIR environment variable instead of adding an option to support this functionality.

       The -k option was added to satisfy two objections. First, the zero-based counting used  by
       sort  is  not  consistent  with  other utility conventions. Second, it did not meet syntax
       guideline requirements.

       Historical documentation indicates that "setting -n implies -b".  The  description  of  -n
       already  states  that optional leading <blank>s are tolerated in doing the comparison.  If
       -b is enabled, rather than implied, by -n, this has unusual side effects. When a character
       offset  is  used  in a column of numbers (for example, to sort modulo 100), that offset is
       measured relative to the  most  significant  digit,  not  to  the  column.  Based  upon  a
       recommendation  from  the author of the original sort utility, the -b implication has been
       omitted from this volume of IEEE Std 1003.1-2001, and an application  wishing  to  achieve
       the previously mentioned side effects has to code the -b flag explicitly.




       comm , join , uniq , the System Interfaces volume of IEEE Std 1003.1-2001, toupper()


       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2003 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
       the Institute of Electrical and Electronics Engineers, Inc and  The  Open  Group.  In  the
       event  of  any  discrepancy  between this version and the original IEEE and The Open Group
       Standard, the original IEEE and The Open Group  Standard  is  the  referee  document.  The
       original Standard can be obtained online at .