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XARGS(1) XARGS(1)
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 pro-
cessed 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 separa-
tor. 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 imme-
diately 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 redi-
rected 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 liter-
ally). 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 depre-
cated 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 argu-
ments 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 com-
mand. 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 log-
ical 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://savan-
nah.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 bug-findutils-request AT gnu.org.
XARGS(1)
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