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] [-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] [--inter- active] [--verbose] [--exit] [--no-run-if-empty] [--arg-file=file] [--version] [--help] [command [ini- tial-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 stan- dard 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 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 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 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. --eof[=eof-str], -E[eof-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 eof-str is omitted, there is no end of file string. If this option is not given, no end of file string is used. -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. --help Print a summary of the options to xargs and exit. --replace[=replace-str], -i[replace-str] Replace occurences 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 char- acter. If replace-str is omitted, it defaults to "{}" (like for `find -exec'). Implies -x and -l 1. --max-lines[=max-lines], -L[max-lines] Use at most max-lines nonblank input lines per command line; max-lines defaults to 1 if omitted. Trailing blanks cause an input line to be logi- cally continued on the next input line. Implies -x. -l[max-lines] Deprecated; non-POSIX-compliant synonym for the -L option. --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 non- blanks, 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 charac- ters, not including the size of the environment variables (which are provided for separately so that it doesn't matter if your environment vari- ables take up more than 131072 bytes). The oper- ating 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 out- put 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 sys- tem. 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. SEE ALSO find(1), locate(1), locatedb(5), updatedb(1), Finding Files (on-line in Info, or printed) BUGS 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 alter- native. 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 rea- son 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@gnu.org. XARGS(1)