xargs(1) - NetBSD Manual Pages

XARGS(1)                NetBSD General Commands Manual                XARGS(1)


NAME

     xargs -- construct argument list(s) and execute utility


SYNOPSIS

     xargs [-0oprt] [-E eofstr] [-I replstr [-R replacements] [-S replsize]]
           [-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 utility with the strings as
     arguments.

     Any arguments specified on the command line are given to utility upon
     each invocation, followed by some number of the arguments read from the
     standard input of xargs.  This is repeated 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 charac-
     ters, 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.  This 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 occur-
             rences 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 replsize (or 255 if no -S flag is speci-
             fied) bytes; this is implemented by concatenating as much of the
             argument containing replstr as possible, to the constructed argu-
             ments to utility, up to replsize bytes.  The size 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 affect 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 dis-
             tinct 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 lines read.  If EOF is reached and
             fewer lines have been read than number 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 interac-
             tive 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      Compatibility with GNU xargs.  The GNU version of xargs runs the
             utility argument at least once, even if xargs input is empty, and
             it supports a -r option to inhibit this behavior.  The NetBSD
             version of xargs does not run the utility argument on empty
             input, but it supports the -r option for command-line compatibil-
             ity with GNU xargs; but the -r option does nothing in the NetBSD
             version of xargs.

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

     -S replsize
             Specify the amount of space (in bytes) that -I can use for
             replacements.  The default for replsize is 255.

     -s size
             Set the maximum number of bytes for the command line length pro-
             vided to utility.  The sum of the length of the utility name, the
             arguments passed to utility (including NULL 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) com-
             mand line length.

     If utility is omitted, 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.


FILES

     /dev/tty  used to read responses in prompt mode


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 sta-
             tus.
     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 invoked.
     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 expected to be IEEE Std 1003.2 (``POSIX.2'') compli-
     ant.  The -J, -o, -P, -R, and -S options are non-standard FreeBSD exten-
     sions which may not be available on other operating systems.


HISTORY

     The xargs utility appeared in PWB UNIX 1.0.  It made its first BSD
     appearance in the 4.3 Reno release.

     The meaning of 123, 124, and 125 exit values and the -0 option were taken
     from GNU xargs.


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.

     The xargs utility does not take multibyte characters into account when
     performing string comparisons for the -I and -J options, which may lead
     to incorrect results in some locales.

NetBSD 10.99                   December 21, 2010                  NetBSD 10.99