1XARGS(1) General Commands Manual XARGS(1)
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6 xargs - build and execute command lines from standard input
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9 xargs [-0prtx] [-E eof-str] [-e[eof-str]] [--eof[=eof-str]] [--null]
10 [-d delimiter] [--delimiter delimiter] [-I replace-str] [-i[replace-
11 str]] [--replace[=replace-str]] [-l[max-lines]] [-L max-lines]
12 [--max-lines[=max-lines]] [-n max-args] [--max-args=max-args] [-s max-
13 chars] [--max-chars=max-chars] [-P max-procs] [--max-procs=max-procs]
14 [--interactive] [--verbose] [--exit] [--no-run-if-empty]
15 [--arg-file=file] [--show-limits] [--version] [--help] [command
16 [initial-arguments]]
17
19 This manual page documents the GNU version of xargs. xargs reads items
20 from the standard input, delimited by blanks (which can be protected
21 with double or single quotes or a backslash) or newlines, and executes
22 the command (default is /bin/echo) one or more times with any initial-
23 arguments followed by items read from standard input. Blank lines on
24 the standard input are ignored.
25 Because Unix filenames can contain blanks and newlines, this default
27 behaviour is often problematic; filenames containing blanks and/or new‐
28 lines are incorrectly processed by xargs. In these situations it is
29 better to use the -0 option, which prevents such problems. When using
30 this option you will need to ensure that the program which produces the
31 input for xargs also uses a null character as a separator. If that
32 program is GNU find for example, the -print0 option does this for you.
33 If any invocation of the command exits with a status of 255, xargs will
35 stop immediately without reading any further input. An error message
36 is issued on stderr when this happens.
37
39 --arg-file=file
40 -a file
41 Read items from file instead of standard input. If you use this
42 option, stdin remains unchanged when commands are run. Other‐
43 wise, stdin is redirected from /dev/null.
44 --null
46 -0 Input items are terminated by a null character instead of by
47 whitespace, and the quotes and backslash are not special (every
48 character is taken literally). Disables the end of file string,
49 which is treated like any other argument. Useful when input
50 items might contain white space, quote marks, or backslashes.
51 The GNU find -print0 option produces input suitable for this
52 mode.
53 --delimiter=delim
56 -d delim
57 Input items are terminated by the specified character. Quotes
58 and backslash are not special; every character in the input is
59 taken literally. Disables the end-of-file string, which is
60 treated like any other argument. This can be used when the in‐
61 put consists of simply newline-separated items, although it is
62 almost always better to design your program to use --null where
63 this is possible. The specified delimiter may be a single char‐
64 acter, a C-style character escape such as \n, or an octal or
65 hexadecimal escape code. Octal and hexadecimal escape codes are
66 understood as for the printf command. Multibyte characters are
67 not supported.
68 -E eof-str
71 Set the end of file string to eof-str. If the end of file
72 string occurs as a line of input, the rest of the input is ig‐
73 nored. If neither -E nor -e is used, no end of file string is
74 used.
75 --eof[=eof-str]
77 -e[eof-str]
78 This option is a synonym for the -E option. Use -E instead, be‐
79 cause it is POSIX compliant while this option is not. If eof-
80 str is omitted, there is no end of file string. If neither -E
81 nor -e is used, no end of file string is used.
82 --help Print a summary of the options to xargs and exit.
84 -I replace-str
86 Replace occurrences of replace-str in the initial-arguments with
87 names read from standard input. Also, unquoted blanks do not
88 terminate input items; instead the separator is the newline
89 character. Implies -x and -L 1.
90 --replace[=replace-str]
92 -i[replace-str]
93 This option is a synonym for -Ireplace-str if replace-str is
94 specified, and for -I{} otherwise. This option is deprecated;
95 use -I instead.
96 -L max-lines
98 Use at most max-lines nonblank input lines per command line.
99 Trailing blanks cause an input line to be logically continued on
100 the next input line. Implies -x.
101 --max-lines[=max-lines]
103 -l[max-lines]
104 Synonym for the -L option. Unlike -L, the max-lines argument is
105 optional. If max-lines is not specified, it defaults to one.
106 The -l option is deprecated since the POSIX standard specifies
107 -L instead.
108 --max-args=max-args
110 -n max-args
111 Use at most max-args arguments per command line. Fewer than
112 max-args arguments will be used if the size (see the -s option)
113 is exceeded, unless the -x option is given, in which case xargs
114 will exit.
115 --interactive
117 -p Prompt the user about whether to run each command line and read
118 a line from the terminal. Only run the command line if the re‐
119 sponse starts with `y' or `Y'. Implies -t.
120 --no-run-if-empty
122 -r If the standard input does not contain any nonblanks, do not run
123 the command. Normally, the command is run once even if there is
124 no input. This option is a GNU extension.
125 --max-chars=max-chars
127 -s max-chars
128 Use at most max-chars characters per command line, including the
129 command and initial-arguments and the terminating nulls at the
130 ends of the argument strings. The largest allowed value is sys‐
131 tem-dependent, and is calculated as the argument length limit
132 for exec, less the size of your environment, less 2048 bytes of
133 headroom. If this value is more than 128KiB, 128Kib is used as
134 the default value; otherwise, the default value is the maximum.
135 1KiB is 1024 bytes.
136 --verbose
138 -t Print the command line on the standard error output before exe‐
139 cuting it.
140 --version
142 Print the version number of xargs and exit.
143 --show-limits
145 Display the limits on the command-line length which are imposed
146 by the operating system, xargs' choice of buffer size and the -s
147 option. Pipe the input from /dev/null (and perhaps specify
148 --no-run-if-empty) if you don't want xargs to do anything.
149 --exit
151 -x Exit if the size (see the -s option) is exceeded.
152 --max-procs=max-procs
154 -P max-procs
155 Run up to max-procs processes at a time; the default is 1. If
156 max-procs is 0, xargs will run as many processes as possible at
157 a time. Use the -n option with -P; otherwise chances are that
158 only one exec will be done.
159
161 find /tmp -name core -type f -print | xargs /bin/rm -f
162 Find files named core in or below the directory /tmp and delete them.
164 Note that this will work incorrectly if there are any filenames con‐
165 taining newlines or spaces.
166 find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f
168 Find files named core in or below the directory /tmp and delete them,
170 processing filenames in such a way that file or directory names con‐
171 taining spaces or newlines are correctly handled.
172 find /tmp -depth -name core -type f -delete
175 Find files named core in or below the directory /tmp and delete them,
177 but more efficiently than in the previous example (because we avoid the
178 need to use fork(2) and exec(2) to launch rm and we don't need the ex‐
179 tra xargs process).
180 cut -d: -f1 < /etc/passwd | sort | xargs echo
183 Generates a compact listing of all the users on the system.
185 xargs sh -c 'emacs "$@" < /dev/tty' emacs
188 Launches the minimum number of copies of Emacs needed, one after the
190 other, to edit the files listed on xargs' standard input. This example
191 achieves the same effect as BSD's -o option, but in a more flexible and
192 portable way.
193
198 xargs exits with the following status:
199 0 if it succeeds
200 123 if any invocation of the command exited with status 1-125
201 124 if the command exited with status 255
202 125 if the command is killed by a signal
203 126 if the command cannot be run
204 127 if the command is not found
205 1 if some other error occurred.
206 Exit codes greater than 128 are used by the shell to indicate that a
208 program died due to a fatal signal.
209
211 As of GNU xargs version 4.2.9, the default behaviour of xargs is not to
212 have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edi‐
213 tion) allows this.
214 The -l and -i options appear in the 1997 version of the POSIX standard,
216 but do not appear in the 2004 version of the standard. Therefore you
217 should use -L and -I instead, respectively.
218 The POSIX standard allows implementations to have a limit on the size
220 of arguments to the exec functions. This limit could be as low as 4096
221 bytes including the size of the environment. For scripts to be porta‐
222 ble, they must not rely on a larger value. However, I know of no im‐
223 plementation whose actual limit is that small. The --show-limits op‐
224 tion can be used to discover the actual limits in force on the current
225 system.
226
230 find(1), locate(1), locatedb(5), updatedb(1), fork(2), execvp(3), Find‐
231 ing Files (on-line in Info, or printed)
232
234 The -L option is incompatible with the -I option, but perhaps should
235 not be.
236 It is not possible for xargs to be used securely, since there will al‐
238 ways be a time gap between the production of the list of input files
239 and their use in the commands that xargs issues. If other users have
240 access to the system, they can manipulate the filesystem during this
241 time window to force the action of the commands xargs runs to apply to
242 files that you didn't intend. For a more detailed discussion of this
243 and related problems, please refer to the ``Security Considerations''
244 chapter in the findutils Texinfo documentation. The -execdir option of
245 find can often be used as a more secure alternative.
246 When you use the -I option, each line read from the input is buffered
248 internally. This means that there is an upper limit on the length of
249 input line that xargs will accept when used with the -I option. To
250 work around this limitation, you can use the -s option to increase the
251 amount of buffer space that xargs uses, and you can also use an extra
252 invocation of xargs to ensure that very long lines do not occur. For
253 example:
254 somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}'
256 Here, the first invocation of xargs has no input line length limit be‐
258 cause it doesn't use the -i option. The second invocation of xargs
259 does have such a limit, but we have ensured that the it never encoun‐
260 ters a line which is longer than it can handle. This is not an ideal
261 solution. Instead, the -i option should not impose a line length lim‐
262 it, which is why this discussion appears in the BUGS section. The
263 problem doesn't occur with the output of find(1) because it emits just
264 one filename per line.
265 The best way to report a bug is to use the form at http://savan‐
267 nah.gnu.org/bugs/?group=findutils. The reason for this is that you
268 will then be able to track progress in fixing the problem. Other com‐
269 ments about xargs(1) and about the findutils package in general can be
270 sent to the bug-findutils mailing list. To join the list, send email
271 to bug-findutils-request@gnu.org.
272 XARGS(1)