xargs



XARGS(1)                   OpenBSD Reference Manual                   XARGS(1)


NAME

     xargs - construct argument list(s) and execute utility


SYNOPSIS

     xargs [-0oprt] [-E eofstr] [-I replstr [-R replacements]] [-J replstr]
           [-L number] [-n number [-x]] [-P maxprocs] [-s size]
           [utility [argument ...]]


DESCRIPTION

     The xargs utility reads space, tab, newline, and end-of-file delimited
     strings from the standard input and executes the specified utility with
     the strings as arguments.

     Any arguments specified on the command line are given to the utility upon
     each invocation, followed by some number of the arguments read from
     standard input.  The utility is repeatedly executed one or more times
     until standard input is exhausted.

     Spaces, tabs and newlines may be embedded in arguments using single (`'')
     or double (`"') quotes or backslashes (`\').  Single quotes escape all
     non-single quote characters, excluding newlines, up to the matching
     single quote.  Double quotes escape all non-double quote characters,
     excluding newlines, up to the matching double quote.  Any single
     character, including newlines, may be escaped by a backslash.

     The options are as follows:

     -0      Change xargs to expect NUL (`\0') characters as separators,
             instead of spaces and newlines.  The quoting mechanisms described
             above are not performed.  This option is expected to be used in
             concert with the -print0 function in find(1).

     -E eofstr
             Use eofstr as a logical EOF marker.

     -I replstr
             Execute utility for each input line, replacing one or more
             occurrences of replstr in up to replacements (or 5 if no -R flag
             is specified) arguments to utility with the entire line of input.
             The resulting arguments, after replacement is done, will not be
             allowed to grow beyond 255 bytes; this is implemented by
             concatenating as much of the argument containing replstr as
             possible, to the constructed arguments to utility, up to 255
             bytes.  The 255 byte limit does not apply to arguments to utility
             which do not contain replstr, and furthermore, no replacement
             will be done on utility itself.  Implies -x.

     -J replstr
             If this option is specified, xargs will use the data read from
             standard input to replace the first occurrence of replstr instead
             of appending that data after all other arguments.  This option
             will not effect how many arguments will be read from input (-n),
             or the size of the command(s) xargs will generate (-s).  The
             option just moves where those arguments will be placed in the
             command(s) that are executed.  The replstr must show up as a
             distinct argument to xargs.  It will not be recognized if, for
             instance, it is in the middle of a quoted string.  Furthermore,
             only the first occurrence of the replstr will be replaced.  For
             example, the following command will copy the list of files and
             directories which start with an uppercase letter in the current
             directory to destdir:

                   /bin/ls -1d [A-Z]* | xargs -J % cp -Rp % destdir

     -L number
             Call utility for every number of non-empty lines read.  A line
             ending in unescaped white space and the next non-empty line are
             considered to form one single line.  If EOF is reached and fewer
             than number lines have been read then utility will be called with
             the available lines.

     -n number
             Set the maximum number of arguments taken from standard input for
             each invocation of utility.  An invocation of utility will use
             less than number standard input arguments if the number of bytes
             accumulated (see the -s option) exceeds the specified size or
             there are fewer than number arguments remaining for the last
             invocation of utility.  The current default value for number is
             5000.

     -o      Reopen stdin as /dev/tty in the child process before executing
             the command.  This is useful if you want xargs to run an
             interactive application.

     -P maxprocs
             Parallel mode: run at most maxprocs invocations of utility at
             once.

     -p      Echo each command to be executed and ask the user whether it
             should be executed.  An affirmative response, `y' in the POSIX
             locale, causes the command to be executed, any other response
             causes it to be skipped.  No commands are executed if the process
             is not attached to a terminal.

     -R replacements
             Specify the maximum number of arguments that -I will do
             replacement in.  If replacements is negative, the number of
             arguments in which to replace is unbounded.

     -r      Do not run the command if there are no arguments.  Normally the
             command is executed at least once even if there are no arguments.

     -s size
             Set the maximum number of bytes for the command line length
             provided to utility.  The sum of the length of the utility name,
             the arguments passed to utility (including NUL terminators) and
             the current environment will be less than or equal to this
             number.  The current default value for size is ARG_MAX - 4096.

     -t      Echo the command to be executed to standard error immediately
             before it is executed.

     -x      Force xargs to terminate immediately if a command line containing
             number arguments will not fit in the specified (or default)
             command line length.

     If no utility is specified, echo(1) is used.

     Undefined behavior may occur if utility reads from the standard input.

     The xargs utility exits immediately (without processing any further
     input) if a command line cannot be assembled, utility cannot be invoked,
     an invocation of utility is terminated by a signal, or an invocation of
     utility exits with a value of 255.


EXIT STATUS

     xargs exits with one of the following values:

           0       All invocations of utility returned a zero exit status.
           123     One or more invocations of utility returned a nonzero exit
                   status.
           124     The utility exited with a 255 exit status.
           125     The utility was killed or stopped by a signal.
           126     The utility was found but could not be executed.
           127     The utility could not be found.
           1       Some other error occurred.


SEE ALSO

     echo(1), find(1), execvp(3)


STANDARDS

     The xargs utility is compliant with the IEEE Std 1003.1-2008
     (``POSIX.1'') specification.

     The flags -I and -L are compliant with the X/Open Portability Guide
     Issue 4 (``XPG4'') specification.

     The flags [-0JoPRr] are extensions to those specifications.

     The meanings of the 123, 124, and 125 exit values were taken from GNU
     xargs.


HISTORY

     The xargs command appeared in PWB UNIX.


BUGS

     If utility attempts to invoke another command such that the number of
     arguments or the size of the environment is increased, it risks execvp(3)
     failing with E2BIG.

OpenBSD 5.4                    September 3, 2010                   OpenBSD 5.4

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