Provided by: sash_3.8-5_amd64 bug

NAME

       sash - stand-alone shell with built-in commands

SYNOPSYS

       sash [-c command] [-f fileName ] [-p prompt] [-q] [-a]

DESCRIPTION

       The  sash program is a stand-alone shell which is useful for recovering from certain types
       of system failures.  In particular, it was created in order to cope with  the  problem  of
       missing shared libraries or important executables.

       Sash  can  execute external programs, as in any shell.  There are no restrictions on these
       commands, as the standard shell is used to execute them  if  there  are  any  non-wildcard
       meta-characters in the command.

       More  importantly,  however,  is that many of the standard system commands are built-in to
       sash.  These built-in commands are:

            -ar, -chattr, -chgrp, -chmod, -chown, -chroot, -cmp,
            -cp, -dd, -echo, -ed, -grep, -file, -find, -gunzip,
            -gzip, -kill, -losetup, -ln, -ls, -lsattr, -mkdir,
            -mknod, -more, -mount, -mv, -pivot_root, -printenv, -pwd,
            -rm, -rmdir, -sum, -sync, -tar, -touch, -umount, -where

       These commands are  generally  similar  to  the  standard  programs  with  similar  names.
       However,  they  are  simpler  and  cruder  than  the external programs, and so many of the
       options are not implemented.  The restrictions for each  built-in  command  are  described
       later.

       The built-in commands which correspond to external programs begin with a dash character in
       order to distinguish them from the external programs.  So typing "ls", for  example,  will
       attempt  to  run  the real ls program.  If "-ls" is typed, then the built-in command which
       mimics ls is called.

       For the built-in commands, file names are expanded so that asterisks, question marks,  and
       characters  inside  of  square brackets are recognised and are expanded.  Arguments can be
       quoted using single quotes, double quotes, or backslashes.  However, no other command line
       processing is performed.  This includes specifying of file redirection, and the specifying
       of a pipeline.

       If an external program is non-existant or fails to run correctly, then the "alias"  built-
       in  command may be used to redefine the standard command so that it automatically runs the
       built-in command instead.  For example, the command "alias ls -ls" redefines "ls"  to  run
       the  built-in  command.  This saves you the pain of having to remember to type the leading
       dash all of the time.  If many external programs will not run, then the "aliasall" command
       may be useful to create multiple aliases.

       The  "help"  command  will  list all of the built-in commands in sash .  If an argument is
       given, it will list only those built-in commands which contain the  given  argument  as  a
       sub-string.  Each built-in command is described below in more detail.

       alias [name [command]]
              If  name  and  command  are  provided, this defines an alias for a command with the
              specified name which  executes  the  specified  command  with  possible  arguments.
              Arguments  containing  wildcards  can  be  quoted in order to defer their expansion
              until the alias is invoked.  If just name is provided, then the definition  of  the
              specified command alias is displayed.  If nothing is provided, then the definitions
              of all aliases are displayed.

       aliasall
              This defines aliases for all of the built-in commands that start with dashes to the
              corresponding  names  without the dashes.  This may be useful when the system is so
              corrupted that no external programs may be executed at all.

       -ar [txp][v] arfile [filename]...
              List or extract files from an ar archive.  The arfile  argument  specifies  a  file
              name  which  contains  the archive.  If no additional filenames are specified, then
              all files in the archive are operated on.  Otherwise, only  those  archive  members
              which  have  the  same  name  as  one  of the additional filenames are operated on.
              Filenames which do not appear in the  archive  are  ignored.   Archives  cannot  be
              created   or  modified.   The  archiver  correctly  handles  4.0BSD  archives,  and
              understands both the SysV and 4.4BSD extensions for long file names.  The  extended
              pseudo-BSD  formats  are not supported; nor are the two antediluvian binary formats
              derived from V7 and earlier.  (The GNU archiver normally creates  archives  in  the
              4.0BSD format with SysV extensions.)

       cd [dirName]
              If  dirName  is provided, then the current directory is changed to the dirName.  If
              dirName is absent, then the  current  directory  is  changed  to  the  user's  home
              directory (value of the $HOME environment variable).

       -chattr [+i] [-i] [+a] [-a] fileName ...
              Change the attributes of the specified files on an ext2 or ext3 file system.  Using
              a plus sign adds the specified attribute for the files.  Using a minus sign removes
              the  specified  attributes for the files.  The 'i' attribute makes a file immutable
              so that it cannot be changed.  The 'a' attribute makes a  file  append-only.   This
              command is only available on Linux.

       -chgrp gid fileName ...
              Change the group id for the specified list of files.  The gid can either be a group
              name, or a decimal value.

       -chmod mode fileName ...
              Change the mode of the specified list of files.  The mode argument can only  be  an
              octal value.

       -chown uid fileName ...
              Change  the owner id for the specified list of files.  The uid can either be a user
              name, or a decimal value.

       -chroot path
              Changes  the  root  directory to that specified in path.  This  directory  will  be
              used  for  path   names   beginning  with /. The root directory is inherited by all
              children of the current process.

       -cmp fileName1 fileName2
              Determines whether or not the specified file names have identical data.  This  says
              that the files are links to each other, are different sizes, differ at a particular
              byte number, or are identical.

       -cp srcName ... destName
              Copies one or more files from the srcName  to  the  destName.   If  more  than  one
              srcName  is  given, or if destName is a directory, then all the srcNames are copied
              into the destName directory with the same names as the srcNames.

       -dd if=name of=name [bs=n] [count=n] [skip=n] [seek=n]
              Copy data from one file to another with the specified parameters.  The  if  and  of
              arguments  must  be  provided,  so  stdin  and  stdout cannot be specified.  The bs
              argument is the block size, and is a numeric value (which defaults to  512  bytes).
              Count  is  the number of blocks to be copied (which defaults to end of file for the
              input file).  Skip is the number of blocks to ignore before copying (seek  is  used
              if  possible,  and  the default is 0).  Seek is the number of blocks to seek in the
              output file before writing (and defaults to 0).  Any of the numeric decimal  values
              can  have  one  or  more  trailing letters from the set 'kbw', which multiplies the
              value by 1024, 512, and 2 respectively.  The command reports  the  number  of  full
              blocks read and written, and whether or not any partial block was read or written.

       -echo [args] ...
              Echo  the  arguments  to  the  -echo command.  Wildcards are expanded, so this is a
              convenient way to get a quick list of file names in a  directory.   The  output  is
              always terminated with a newline.

       -ed [fileName]
              Edit  the  specified  file using line-mode commands.  The following ed commands are
              provided: = c r w i a d p l s f k z and q.  Line numbers  can  be  constants,  ".",
              "$",  "'x",  /string/  and simple arithmetic combinations of these.  The substitute
              command and the search expression can only use literal  strings.   There  are  some
              small differences in the way that some commands behave.

       exec fileName [args]
              Execute  the  specified  program  with the specified arguments.  This replaces sash
              completely by the executed program.

       exit   Quit from sash.

       -file fileName ...
              Examine the specified files and print out their file type.  This indicates  whether
              the  files  are  regular files or not, whether they contain printable text or shell
              scripts, are executables, or contain binary data.

       -find dirName [-xdev] [-type chars] [-name pattern] [-size minSize]
              Find all files contained within the specified directory tree which meet all of  the
              specified  conditions.   The  -xdev  option prevents crossing of mount points.  The
              -name option specifies a wildcard pattern to match the last component of  the  file
              names.   The  -type  option  specifies that the files must have a type matching the
              specified list from the set: f d c  b  p  s  l.   These  represent  regular  files,
              directories,  character  devices, block devices, named pipes, sockets, and symbolic
              links.  The -size option  specifies  that  the  files  must  be  regular  files  or
              directories which contain at least the specified number of bytes.

       -grep [-in] word fileName ...
              Display  lines  of  the  specified files which contain the given word.  If only one
              file name is given, then only the matching lines are  printed.   If  multiple  file
              names  are  given,  then  the file names are printed along with the matching lines.
              Word must be a single word, (ie, not a regular expression).  If -i is  given,  then
              case  is  ignored  when doing the search.  If -n is given, then the line numbers of
              the matching lines are also printed.

       -gunzip inputFileName ... [-o outputPath]
              Uncompress one or more files that had been compressed using the  gzip  or  compress
              algorithms.   If the -o option is not given, then each of the input file names must
              have one of the extensions ".gz", ".tgz", or ".Z", and those files will be replaced
              by  the  uncompressed  versions of those files.  The original files will be deleted
              after the output files have been successfully created.  The  uncompressed  versions
              of  the  files  have the same names as the original file names, except for a simple
              modification of their extensions.  If an extension is ".tgz", then the extension is
              replaced by ".tar".  Otherwise, the ".gz" or ".Z" extension is removed.

              If  the  -o  option  is  given,  then  the input files will not be deleted, and the
              uncompressed versions of the files will be created as specified by outputPath.   If
              the  output  path is a directory, then the uncompressed versions of the input files
              will be placed in that directory with their file names modified as described above,
              or  with  the  same  name  if  the input file name does not have one of the special
              extensions.  If the output path is a regular file, then  only  one  input  file  is
              allowed,  and  the uncompressed version of that input file is created as the output
              path exactly as specified.  If the output path is a block or character device, then
              the uncompressed versions of the input files are concatenated to the device.

              This command is only available if sash was compiled to use the gzip library.

       -gzip inputFileName ... [-o outputPath]
              Compresses  one  or  more  files using the gzip algorithm.  If the -o option is not
              given, then each of the input  file  names  will  be  replaced  by  the  compressed
              versions  of those files, The original files will be deleted after the output files
              have been successfully created.  The compressed versions of the files have the same
              names  as  the  original  file  names,  except  for  a  simple  modification of the
              extensions.  If an extension is ".tar", then the extension is replaced  by  ".tgz".
              Otherwise, the ".gz" extension is added.

              If  the  -o  option  is  given,  then  the input files will not be deleted, and the
              compressed versions of the files will be created as specified  by  outputPath.   If
              the  output  path  is  a directory, then the compressed versions of the input files
              will be placed in that directory with their file names modified as described above.
              If the output path is not a directory, then only one input file is allowed, and the
              compressed version of that input file is created as  the  output  path  exactly  as
              specified.

              This command is only available if sash was compiled to use the gzip library.

       help [word]
              Displays  a list of built-in commands along with their usage strings.  If a word is
              given, then just those commands whose name or usage contains the word is displayed.
              If  a word is specified which exactly matches a built-in command name, then a short
              description of the command and its usage is given.

       -kill [-signal] pid ...
              Sends the specified signal to the specified list of processes.  Signal is a numeric
              value, or one of the special values HUP, INT, QUIT, KILL, TERM, STOP, CONT, USR1 or
              USR2.  If no signal is specified then SIGTERM is used.

       -losetup [-d] loopDev [file]
              Associates loopback devices with files on the system.  If  -d  is  not  given,  the
              loopback  device  loopDev  is  associated  with  file.   If -d is given, loopDev is
              unassociated with the file it's currently configured for.

       -ln [-s] srcName ... destName
              Links one or more files from the srcName to the specified destName.  If  there  are
              multiple srcNames, or destName is a directory, then the link is put in the destName
              directory with the same name as the source name.  The default links are hard links.
              Using  -s  makes  symbolic  links.   For  symbolic  links,  only one srcName can be
              specified.

       -ls [-lidFC] fileName ...
              Display information about the specified list of file names.  The normal listing  is
              simply  a  list of file names, one per line.  The options available are -l, -n, -i,
              -d, and -F.  The  -l  option  produces  a  long  listing  giving  the  normal  'ls'
              information.   The  -n option is like -l except that numeric user and group ids are
              shown.  The -i option displays the inode numbers  of  the  files.   The  -d  option
              displays  information  about  a  directory, instead of the files within it.  The -F
              option appends a slash or asterisk to the file name if the file is a  directory  or
              is  executable.   The  -C  option displays the file names in a multi-column format.
              The width of the output is calculated using the COLS environment variable.

       -lsattr fileName ...
              Display attributes for the specified files on an ext2 or  ext3  file  system.   The
              letter  'i' indicates that the file is immutable and cannot change.  The letter 'a'
              indicates that the file is append-only.  Dashes are shown where the attributes  are
              not set.  This command is only available on Linux.

       -mkdir dirName ...
              Creates the specified directories.  They are created with the default permissions.

       -mknod fileName type major minor
              Creates  a  special device node, either a character file or a block file.  Filename
              is the name of the node.  Type is either 'c' or 'd'.  Major  is  the  major  device
              number.  Minor is the minor device number.  Both of these numbers are decimal.

       -more fileName ...
              Type  out  the  contents of the specified file names, one page at a time.  For each
              page displayed, you can type 'n' and a return to go to the next  file,  'q'  and  a
              return  to  quit  the  command completely, or just a return to go to the next page.
              The environment variables LINES and COLS can be used to set the page size.

       -mount [-t type] [-r] [-s] [-e] [-m] devName dirName
              Mount a filesystem on a directory name.   The  -t  option  specifies  the  type  of
              filesystem  being mounted, and defaults to "ext3" for Linux and "ffs" for BSD.  The
              -r option indicates to mount the filesystem read-only.  The -s option indicates  to
              mount  the filesystem no-suid.  The -e option indicates to mount the filesystem no-
              exec.  The -m option indicates to remount an already mounted  filesystem.   The  -m
              option is only available on Linux.

       -mv srcName ... destName
              Moves one or more files from the srcName to the destName.  If multiple srcNames are
              given, or if destName is a  directory,  then  the  srcNames  are  copied  into  the
              destination  directory  with the same names as the srcNames.  Renames are attempted
              first, but if this fails because of the files being on different filesystems,  then
              copies and deletes are done instead.

       -pivot_root newRoot putOld
              Moves the root file system of the current process to the directory putOld and makes
              newRoot the  new root file system of the current process.

       -printenv [name]
              If name is not given, this prints out the values of  all  the  current  environment
              variables.  If name is given, then only that environment variable value is printed.

       prompt [word] ...
              Sets  the  prompt string that is displayed before reading of a command.  A space is
              always added to the specified prompt.

       -pwd   Prints the current working directory.

       quit   Exits from sash.

       -rm fileName ...
              Removes one or more files.

       -rmdir dirName ...
              Removes one or more directories.  The directories must be  empty  for  this  to  be
              successful.

       setenv name value
              Set the value of an environment variable.

       source fileName
              Execute commands which are contained in the specified file name.

       -sum fileName ...
              Calculates checksums for one or more files.  This is the 16 bit checksum compatible
              with the BSD sum program.

       -sync  Do a "sync" system call to force dirty blocks out to the disk.

       -tar [ctxv]f tarFileName [fileName] ...
              Create, list or extract files from a tar archive.  The f option must be  specified,
              and  accepts  a  device or file name argument which contains the tar archive.  When
              creating, at least one file name must be specified to be stored.  If a file name is
              a  directory,  then  all the files and directories within the directory are stored.
              Linked files and other special file types are not handled properly.   When  listing
              or  extracting  files,  only those files starting with the specified file names are
              processed.  If no file names are specified, then  all  files  in  the  archive  are
              processed.   Leading  slashes  in  the tar archive file names are always removed so
              that you might need to cd to "/" to restore files which had absolute paths.

       -touch fileName ...
              Updates the modify times of the specifed files.  If a file does not exist, then  it
              will be created with the default protection.

       umask [mask]
              If  mask  is given, sets the "umask" value used for initializing the permissions of
              newly created files.  If mask is  not  given,  then  the  current  umask  value  is
              printed.  The mask is an octal value.

       -umount [-f] fileName
              Unmounts  a  file  system.   The  file  name can either be the device name which is
              mounted, or else the directory name which the file system is mounted onto.  The  -f
              option  unmounts  the  filesystem  even if it is being used.  The -f option is only
              available on BSD.

       unalias name
              Remove the definition for the specified alias.

       -where program
              Prints out all of  paths  defined  by  the  PATH  environment  variable  where  the
              specified  program  exists.  If the program exists but cannot be executed, then the
              reason is also printed.

OPTIONS

       There are several command line options to sash.

       The -c option executes the next argument  as  a  command  (including  embedded  spaces  to
       separate the arguments of the command), and then exits.

       The  -f  option  executes  the  commands  contained in the file name specified by the next
       argument, and then exits.  This feature can be used to create executable scripts for  sash
       by starting the script file with a line similar to:
            #! /bin/sash -f

       The  -p  option takes the next argument as the prompt string to be used when prompting for
       commands.

       The -q option makes sash quiet, which simply means that it doesn't print its  introduction
       line when it starts.  This option is also implied if the -c or -f options are used.

       The  -a  option  creates  aliases  for  the  built-in  commands  so  that they replace the
       corresponding standard commands.  This is the same result as if the 'aliasall' command was
       used.

SYSTEM RECOVERY

       This section contains some useful information about using sash with lilo to perform system
       recovery in some situations.  Similar concepts should exist for  other  boot  loaders  and
       operating systems.

       When  important  shared libraries are being upgraded, it might be a good idea to have sash
       already running on a console by itself.  Then if  there  is  a  problem  with  the  shared
       libraries sash will be unaffected and you may be able to use it to fix the problem.

       If  a  problem  with  the system shows up at boot time so that you cannot enter multi-user
       mode and log in, then you can first try booting into single-user mode by adding the single
       keyword  after  your kernel image name at the lilo prompt.  If you manage to reach a shell
       prompt, then you can run sash from that shell (if necessary).  One reason for  doing  this
       is  that  you  might need to use the -mount command with the -m option to remount the root
       file system so that it can be modified.

       If you cannot reach the shell in single-user mode, then you can try running sash  directly
       as  a replacement for the init process.  This is done by adding the init=/bin/sash keyword
       after your kernel image name at the lilo prompt.  When this is done, then the use  of  the
       aliasall  command  might  be useful to reduce attempts to access the root file system when
       running commands.

       If your root file system is so corrupted that you cannot get sash to run at all, then  you
       will have to resort to a system recovery floppy.

WARNINGS

       Sash should obviously be linked statically, otherwise its purpose is lost.  Note that even
       if the rest of the program is linked statically, the password and group lookup routines in
       the  C library can still be dynamic.  For that reason, if there are problems then it might
       be necessary to only use numeric ids for the -chown and -chgrp commands and to use the  -n
       option instead of -l for the -ls command.

       Several  other system commands might be necessary for system recovery, but aren't built-in
       to sash.

AUTHOR

       David I. Bell
       dbell@tip.net.au
       5 March 2014

                                                                                          SASH(1)