XE(1)                       General Commands Manual                      XE(1)

NAME
     xe – execute a command for every argument

SYNOPSIS
     xe [-0FLRnqv] [-I replace-arg] [-N maxargs] [-j maxjobs] command ...
     xe [flags ...] -p pattern command ... [+ pattern command ...]...
     xe [flags ...] -f argfile command ...
     xe [flags ...] -s shellscript
     xe [flags ...] -a command ... -- args ...
     xe [flags ...] -A argsep command ... argsep args ...

DESCRIPTION
     The xe utility constructs command lines from specified arguments,
     combining some of the best features of xargs(1) and apply(1).

     xe means “execute for every ...”.

     xe supports different methods to specify arguments to commands:

     command ...
             By default, arguments - separated by newlines - are read from the
             standard input.  The resulting command is constructed from the
             command line parameters, replacing replace-arg with the read
             argument, and is executed with execvp(3).

             In this mode, no shell is involved and replace-arg must appear as
             a word on its own, i.e.  ‘foo {} bar’ will work, but ‘foo{} bar’
             will not, where {} is the default value for replace-arg.

             If no argument is specified, the default is ‘printf %s\n’.

     -f argfile
             Read arguments from argfile, instead of the standard input.

             This does not close the standard input for execution, it is
             passed to the forked process.

     -s shellscript
             In this mode, the single parameter shellscript is executed using
             sh -c.  In the script, the specified arguments can be accessed
             using $1, $2, ...

             For example:
                   echo 'a\nb' | xe -N2 -s 'echo $2 $1'

     -a command ... -- args ...
             In this mode, everything after -- is passed as args to command.

     -A argsep command ... argsep args ...
             Same as -a, but the custom argument separator argsep is used to
             distinguish between command and its args.

     The options are as follows:

     -0      Input filenames are separated by NUL bytes (instead of newlines,
             which is the default)

     -F      Fatal: stop and exit when a command execution fails.

     -L      Run the resulting commands with line-buffered output; lines from
             two jobs will not interleave.  When used twice, or with -vv, also
             prefix each line with the number of the job (see ENVIRONMENT) in
             such a manner that the output can be piped to ‘sort -snk1’ to
             group it.

     -R      Return with status 122 when no arguments have been specified
             (instead of 0, the default).  xe never executes a command when no
             arguments are specified.

     -n      Dry run: don't run the resulting commands, just print them.

     -q      Quiet mode: redirect standard output and standard error of
             commands to /dev/null.

     -v      Verbose: print commands to standard error before running them.
             When used twice, also print job id and exit status for each
             command.

     -p      Enable make(1)-style percent rules.  The first argument of
             command ... is regarded as a pattern, see PERCENT RULES below.
             Patterns without a slash (or ‘**’) are matched against the
             basenames only.

             Multiple runs of patterns and commands are separated by ‘+’.
             Only the first matching percent rule is executed; in case no
             pattern matches, no command is run.

     -I replace-arg
             Replace first occurrence of replace-arg (default: {}) in the
             resulting command with the argument(s).  Pass an empty
             replace-arg to disable the replace function.  Contrary to
             xargs(1) this will expand into multiple arguments when needed.

     -N maxargs
             Pass up to maxargs arguments to each command (default: 1).
             Using -N0 will pass as many arguments as possible.

     -j maxjobs
             Run up to maxjobs processes concurrently.  Using -j0 will run as
             many processes as there are CPU cores running.  If maxjobs ends
             with an ‘x’, it is regarded as a multiplier of the number of
             running CPU cores (rounded down, but using at least one core).

PERCENT RULES
     The percent rules of xe are similar to the globs of sh(1) or fnmatch(3):
     ‘?’ matches a single character that is not ‘/’.  ‘/’ matches one or
     multiple ‘/’ in the string.  ‘*’ matches zero or more characters, but
     never ‘/’.  ‘**’ matches zero or more characters, including ‘/’.  Note
     that all of these also match leading dots in file names.

     ‘{a,b,c}’ matches either a, b or c.  ‘[abc]’ matches one of the
     characters abc (but never ‘/’).  ‘[!abc]’ matches all characters but abc.
     Alternatively, ‘[^abc]’ can be used too.  ‘[a-c]’ matches any character
     in the range between a and c inclusive.  In character ranges, characters
     can be escaped using a backslash.

     In the pattern, a single occurrence of ‘%’ matches one or more
     characters, and replaces the first occurrence of ‘%’ with the matched
     string in the remaining arguments, which are then used as the command to
     be executed.

ENVIRONMENT
     The environment variable ITER is passed to the child process and
     incremented on each command execution.

EXIT STATUS
     xe follows the convention of GNU and OpenBSD xargs:
     0       on success
     123     if any invocation of the command exited with status 1 to 125.
     124     if the command exited with status 255
     125     if the command was killed by a signal
     126     if the command cannot be run
     127     if the command was not found
     1       if some other error occurred

     Additionally, 122 is returned when -R was passed and the command was
     never executed.

EXAMPLES
     Compress all .c files in the current directory, using all CPU cores:
           xe -a -j0 gzip -- *.c
     Remove all empty files, using lr(1):
           lr -U -t 'size == 0' | xe -N0 rm
     Convert .mp3 to .ogg, using all CPU cores:
           xe -a -j0 -s 'ffmpeg -i "${1}" "${1%.mp3}.ogg"' -- *.mp3
     Same, using percent rules:
           xe -a -j0 -p %.mp3 ffmpeg -i %.mp3 %.ogg -- *.mp3
     Similar, but hiding output of ffmpeg, instead showing spawned jobs:
           xe -ap -j0 -vvq '%.{m4a,ogg,opus}' ffmpeg -y -i {} out/%.mp3 -- *

SEE ALSO
     apply(1), parallel(1), xapply(1), xargs(1)

AUTHORS
     Leah Neukirchen <leah@vuxu.org>

LICENSE
     xe is in the public domain.

     To the extent possible under law, the creator of this work has waived all
     copyright and related or neighboring rights to this work.

           http://creativecommons.org/publicdomain/zero/1.0/

Void Linux                     November 3, 2017                     Void Linux
