NAME
xargs - build and execute command lines from standard
input
SYNOPSIS
xargs [-0prtx] [-E eof-str] [-e[eof-str]]
[--eof[=eof-str]] [--null] [-d delimiter] [--delimiter delimiter]
[-I replace-str] [-i[replace-str]] [--replace[=replace-str]]
[-l[max-lines]] [-L max-lines] [--max-lines[=max-lines]] [-n
max-args] [--max-args=max-args] [-s max-chars]
[--max-chars=max-chars] [-P max-procs] [--max-procs=max-procs]
[--interactive] [--verbose] [--exit] [--no-run-if-empty]
[--arg-file=file] [--version] [--help] [command
[initial-arguments]]
DESCRIPTION
This manual page documents the GNU version of
xargs. xargs reads items from the standard input,
delimited by blanks (which can be protected with double or single
quotes or a backslash) or newlines, and executes the command
(default is /bin/echo) one or more times with any
initial-arguments followed by items read from standard
input. Blank lines on the standard input are ignored. Because Unix
filenames can contain blanks and newlines, this default behaviour
is often problematic; filenames containing blanks and/or newlines
are incorrectly processed by xargs. In these situations it
is better to use the `-0' option, which prevents such problems.
When using this option you will need to ensure that the program
which produces the input for xargs also uses a null
character as a separator. If that program is GNU find for
example, the `-print0' option does this for you. If any invocation
of the command exits with a status of 255, xargs will stop
immediately without reading any further input. An error message is
issued on stderr when this happens.
OPTIONS
- --arg-file=file, -a file
- Read items from file instead of standard input. If you
use this option, stdin remains unchanged when commands are run.
Otherwise, stdin is redirected from /dev/null.
- --null, -0
- Input items are terminated by a null character instead of by
whitespace, and the quotes and backslash are not special (every
character is taken literally). Disables the end of file string,
which is treated like any other argument. Useful when input items
might contain white space, quote marks, or backslashes. The GNU
find -print0 option produces input suitable for this mode.
- --delimiter=delim, -d delim
- Input items are terminated by the specified character. Quotes
and backslash are not special; every character in the input is
taken literally. Disables the end-of-file string, which is treated
like any other argument. This can be used when the input consists
of simply newline-separated items, although it is almost always
better to design your program to use `--null' where this is
possible. The specified delimiter may be a single character, a
C-style character escape such as \n, or an octal or
hexadecimal escape code. Octal and hexadecimal escape codes are
understood as for the printf command. Multibyte characters
are not supported.
- -Eeof-str
- Set the end of file string to eof-str. If the end of
file string occurs as a line of input, the rest of the input is
ignored. If neither -E nor -e is used, no end of file string is
used.
- --eof[=eof-str], -e[eof-str]
- This option is a synonym for the `-E' option. Use `-E' instead,
because it is POSIX compliant while this option is not. If
eof-str is omitted, there is no end of file string. If
neither -E nor -e is used, no end of file string is used.
- --help
- Print a summary of the options to xargs and exit.
- -I replace-str
- Replace occurrences of replace-str in the
initial-arguments with names read from standard input. Also,
unquoted blanks do not terminate input items; instead the separator
is the newline character. Implies -x and -L 1.
- --replace[=replace-str], -i[replace-str]
- This option is a synonym for -Ireplace-str if
replace-str is specified, and for -I{} otherwise. This
option is deprecated; use -I instead.
- -L max-lines
- Use at most max-lines nonblank input lines per command
line. Trailing blanks cause an input line to be logically continued
on the next input line. Implies -x.
- --max-lines[=max-lines], -l[max-lines]
- Synonym for the -L option. Unlike -L, the max-lines
argument is optional. If max-args is not specified, it
defaults to one. The -l option is deprecated since the POSIX
standard specifies -L instead.
- --max-args=max-args, -n max-args
- Use at most max-args arguments per command line. Fewer
than max-args arguments will be used if the size (see the -s
option) is exceeded, unless the -x option is given, in which case
xargs will exit.
- --interactive, -p
- Prompt the user about whether to run each command line and read
a line from the terminal. Only run the command line if the response
starts with `y' or `Y'. Implies -t.
- --no-run-if-empty, -r
- If the standard input does not contain any nonblanks, do not
run the command. Normally, the command is run once even if there is
no input. This option is a GNU extension.
- --max-chars=max-chars, -s max-chars
- Use at most max-chars characters per command line,
including the command and initial-arguments and the terminating
nulls at the ends of the argument strings. The default is 131072
characters, not including the size of the environment variables
(which are provided for separately so that it doesn't matter if
your environment variables take up more than 131072 bytes). The
operating system places limits on the values that you can usefully
specify, and if you exceed these a warning message is printed and
the value actually used is set to the appropriate upper or lower
limit.
- --verbose, -t
- Print the command line on the standard error output before
executing it.
- --version
- Print the version number of xargs and exit.
- --exit, -x
- Exit if the size (see the -s option) is exceeded.
- --max-procs=max-procs, -P max-procs
- Run up to max-procs processes at a time; the default is
1. If max-procs is 0, xargs will run as many
processes as possible at a time. Use the -n option with
-P; otherwise chances are that only one exec will be
done.
EXAMPLES
find /tmp -name core -type f -print | xargs /bin/rm -f
Find files named core in or below the directory /tmp
and delete them. Note that this will work incorrectly if there are
any filenames containing newlines or spaces. find /tmp -name
core -type f -print0 | xargs -0 /bin/rm -f
Find files named core in or below the directory
/tmp and delete them, processing filenames in such a way
that file or directory names containing spaces or newlines are
correctly handled.
cut -d: -f1 < /etc/passwd | sort | xargs echo
Generates a compact listing of all the users on the system.
EXIT STATUS
xargs exits with the following status:
0 if it succeeds
123 if any invocation of the command exited with status 1-125
124 if the command exited with status 255
125 if the command is killed by a signal
126 if the command cannot be run
127 if the command is not found
1 if some other error occurred.
Exit codes greater than 128 are used by the shell to indicate that
a program died due to a fatal signal.
STANDARDS CONFORMANCE
As of GNU xargs version 4.2.9, the
default behaviour of xargs is not to have a logical
end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edition) allows
this. The -l and -i options appear in the 1997 version of the POSIX
standard, but do not appear in the 2004 version of the standard.
Therefore you should use -L and -I instead, respectively.
SEE ALSO
find(1),
locate(1),
locatedb(5),
updatedb(1),
Finding Files (on-line in Info, or printed)
BUGS
The -L option is incompatible with the -I option, but
perhaps should not be. It is not possible for xargs to be
used securely, since there will always be a time gap between the
production of the list of input files and their use in the commands
that xargs issues. If other users have access to the system,
they can manipulate the filesystem during this time window to force
the action of the commands xargs runs to apply to files that
you didn't intend. For a more detailed discussion of this and
related problems, please refer to the ``Security Considerations''
chapter in the findutils Texinfo documentation. The -execdir option
of find can often be used as a more secure alternative.
When you use the -I option, each line read from the input is
buffered internally. This means that there is an upper limit on the
length of input line that xargs will accept when used with
the -I option. To work around this limitation, you can use the -s
option to increase the amount of buffer space that xargs
uses, and you can also use an extra invocation of xargs to
ensure that very long lines do not occur. For example:
somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm
'{}' Here, the first invocation of xargs has no input
line length limit because it doesn't use the -i option. The second
invocation of xargs does have such a limit, but we have
ensured that the it never encounters a line which is longer than it
can handle. This is not an ideal solution. Instead, the -i option
should not impose a line length limit, which is why this discussion
appears in the BUGS section. The problem doesn't occur with the
output of find(1)
because it emits just one filename per line. The best way to report
a bug is to use the form at http://savannah.gnu.org/bugs/?group=findutils.
The reason for this is that you will then be able to track progress
in fixing the problem. Other comments about xargs(1)
and about the findutils package in general can be sent to the
bug-findutils mailing list. To join the list, send email to
.