1XARGS(1) General Commands Manual XARGS(1)
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6 xargs - build and execute command lines from standard input
7
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 [ini‐
16 tial-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
30 using this option you will need to ensure that the program which pro‐
31 duces the input for xargs also uses a null character as a separator.
32 If that program is GNU find for example, the `-print0' option does this
33 for you.
34 If any invocation of the command exits with a status of 255, xargs will
36 stop immediately without reading any further input. An error message
37 is issued on stderr when this happens.
38 OPTIONS
40 --arg-file=file, -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, -0
47 Input items are terminated by a null character instead of by
48 whitespace, and the quotes and backslash are not special (every
49 character is taken literally). Disables the end of file string,
50 which is treated like any other argument. Useful when input
51 items might contain white space, quote marks, or backslashes.
52 The GNU find -print0 option produces input suitable for this
53 mode.
54 --delimiter=delim, -d delim
56 Input items are terminated by the specified character. Quotes
57 and backslash are not special; every character in the input is
58 taken literally. Disables the end-of-file string, which is
59 treated like any other argument. This can be used when the
60 input consists of simply newline-separated items, although it is
61 almost always better to design your program to use `--null'
62 where this is possible. The specified delimiter may be a single
63 character, a C-style character escape such as \n, or an octal or
64 hexadecimal escape code. Octal and hexadecimal escape codes are
65 understood as for the printf command. Multibyte characters are
66 not supported.
67 -Eeof-str
70 Set the end of file string to eof-str. If the end of file
71 string occurs as a line of input, the rest of the input is
72 ignored. If neither -E nor -e is used, no end of file string is
73 used.
74 --eof[=eof-str], -e[eof-str]
76 This option is a synonym for the `-E' option. Use `-E' instead,
77 because it is POSIX compliant while this option is not. If eof-
78 str is omitted, there is no end of file string. If neither -E
79 nor -e is used, no end of file string is used.
80 --help Print a summary of the options to xargs and exit.
82 -I replace-str
84 Replace occurrences of replace-str in the initial-arguments with
85 names read from standard input. Also, unquoted blanks do not
86 terminate input items; instead the separator is the newline
87 character. Implies -x and -L 1.
88 --replace[=replace-str], -i[replace-str]
90 This option is a synonym for -Ireplace-str if replace-str is
91 specified, and for -I{} otherwise. This option is deprecated;
92 use -I instead.
93 -L max-lines
95 Use at most max-lines nonblank input lines per command line.
96 Trailing blanks cause an input line to be logically continued on
97 the next input line. Implies -x.
98 --max-lines[=max-lines], -l[max-lines]
100 Synonym for the -L option. Unlike -L, the max-lines argument is
101 optional. If max-args is not specified, it defaults to one.
102 The -l option is deprecated since the POSIX standard specifies
103 -L instead.
104 --max-args=max-args, -n max-args
106 Use at most max-args arguments per command line. Fewer than
107 max-args arguments will be used if the size (see the -s option)
108 is exceeded, unless the -x option is given, in which case xargs
109 will exit.
110 --interactive, -p
112 Prompt the user about whether to run each command line and read
113 a line from the terminal. Only run the command line if the
114 response starts with `y' or `Y'. Implies -t.
115 --no-run-if-empty, -r
117 If the standard input does not contain any nonblanks, do not run
118 the command. Normally, the command is run once even if there is
119 no input. This option is a GNU extension.
120 --max-chars=max-chars, -s max-chars
122 Use at most max-chars characters per command line, including the
123 command and initial-arguments and the terminating nulls at the
124 ends of the argument strings. The default is 131072 characters,
125 not including the size of the environment variables (which are
126 provided for separately so that it doesn't matter if your envi‐
127 ronment variables take up more than 131072 bytes). The operat‐
128 ing system places limits on the values that you can usefully
129 specify, and if you exceed these a warning message is printed
130 and the value actually used is set to the appropriate upper or
131 lower limit.
132 --verbose, -t
134 Print the command line on the standard error output before exe‐
135 cuting it.
136 --version
138 Print the version number of xargs and exit.
139 --show-limits
141 Display the limits on the command-line length which are imposed
142 by the operating system, xargs' choice of buffer size and the -s
143 option. Pipe the input from /dev/null (and perhaps specify
144 --no-run-if-empty) if you don't want xargs to do anything.
145 --exit, -x
147 Exit if the size (see the -s option) is exceeded.
148 --max-procs=max-procs, -P max-procs
150 Run up to max-procs processes at a time; the default is 1. If
151 max-procs is 0, xargs will run as many processes as possible at
152 a time. Use the -n option with -P; otherwise chances are that
153 only one exec will be done.
154
156 find /tmp -name core -type f -print | xargs /bin/rm -f
157 Find files named core in or below the directory /tmp and delete them.
159 Note that this will work incorrectly if there are any filenames con‐
160 taining newlines or spaces.
161 find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f
163 Find files named core in or below the directory /tmp and delete them,
165 processing filenames in such a way that file or directory names con‐
166 taining spaces or newlines are correctly handled.
167 cut -d: -f1 < /etc/passwd | sort | xargs echo
169 Generates a compact listing of all the users on the system.
171
173 xargs exits with the following status:
174 0 if it succeeds
175 123 if any invocation of the command exited with status 1-125
176 124 if the command exited with status 255
177 125 if the command is killed by a signal
178 126 if the command cannot be run
179 127 if the command is not found
180 1 if some other error occurred.
181 Exit codes greater than 128 are used by the shell to indicate that a
183 program died due to a fatal signal.
184
186 As of GNU xargs version 4.2.9, the default behaviour of xargs is not to
187 have a logical end-of-file marker. POSIX (IEEE Std 1003.1, 2004 Edi‐
188 tion) allows this.
189 The -l and -i options appear in the 1997 version of the POSIX standard,
191 but do not appear in the 2004 version of the standard. Therefore you
192 should use -L and -I instead, respectively.
193
196 find(1), locate(1), locatedb(5), updatedb(1), Finding Files (on-line in
197 Info, or printed)
198
200 The -L option is incompatible with the -I option, but perhaps should
201 not be.
202 It is not possible for xargs to be used securely, since there will
204 always be a time gap between the production of the list of input files
205 and their use in the commands that xargs issues. If other users have
206 access to the system, they can manipulate the filesystem during this
207 time window to force the action of the commands xargs runs to apply to
208 files that you didn't intend. For a more detailed discussion of this
209 and related problems, please refer to the ``Security Considerations''
210 chapter in the findutils Texinfo documentation. The -execdir option of
211 find can often be used as a more secure alternative.
212 When you use the -I option, each line read from the input is buffered
214 internally. This means that there is an upper limit on the length of
215 input line that xargs will accept when used with the -I option. To
216 work around this limitation, you can use the -s option to increase the
217 amount of buffer space that xargs uses, and you can also use an extra
218 invocation of xargs to ensure that very long lines do not occur. For
219 example:
220 somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}'
222 Here, the first invocation of xargs has no input line length limit
224 because it doesn't use the -i option. The second invocation of xargs
225 does have such a limit, but we have ensured that the it never encoun‐
226 ters a line which is longer than it can handle. This is not an ideal
227 solution. Instead, the -i option should not impose a line length
228 limit, which is why this discussion appears in the BUGS section. The
229 problem doesn't occur with the output of find(1) because it emits just
230 one filename per line.
231 The best way to report a bug is to use the form at http://savan‐
233 nah.gnu.org/bugs/?group=findutils. The reason for this is that you
234 will then be able to track progress in fixing the problem. Other com‐
235 ments about xargs(1) and about the findutils package in general can be
236 sent to the bug-findutils mailing list. To join the list, send email
237 to bug-findutils-request@gnu.org.
238 XARGS(1)