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1 .TH XARGS L \" -*- nroff -*-
2 .SH NAME
3 xargs \- build and execute command lines from standard input
4 .SH SYNOPSIS
5 .B xargs
6 [\-0prtx] [\-e[eof-str]] [\-i[replace-str]] [\-l[max-lines]]
7 [\-n max-args] [\-s max-chars] [\-P max-procs] [\-\-null] [\-\-eof[=eof-str]]
8 [\-\-replace[=replace-str]] [\-\-max-lines[=max-lines]] [\-\-interactive]
9 [\-\-max-chars=max-chars] [\-\-verbose] [\-\-exit] [\-\-max-procs=max-procs]
10 [\-\-max-args=max-args] [\-\-no-run-if-empty] [\-\-version] [\-\-help]
11 [command [initial-arguments]]
12 .SH DESCRIPTION
13 This manual page
14 documents the GNU version of
15 .BR xargs .
16 .B xargs
17 reads items from the standard input, delimited by blanks (which can be
18 protected with double or single quotes or a backslash) or newlines,
19 and executes the
20 .I command
21 (default is /bin/echo) one or more times with any
22 .I initial-arguments
23 followed by items read from standard input. Blank lines on the
24 standard input are ignored.
25 .P
26 Because Unix filenames can contain blanks and newlines, this default
27 behaviour is often problematic; filenames containing blanks
28 and/or newlines are incorrectly processed by
29 .BR xargs .
30 In these situations it is better to use the `-0' option, which
31 prevents such problems. When using this option you will need to
32 ensure that the program which produces the input for
33 .B xargs
34 also uses a null character as a separator. If that program is
35 GNU
36 .B find
37 for example, the `-print0' option does this for you.
38 .P
39 If any invocation of the command exits with a status of 255,
40 .B xargs
41 will stop immediately without reading any firther input. An error
42 message is issued on stderr when this happens.
43 .SS OPTIONS
44 .TP
45 .I "\-\-null, \-0"
46 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, which
49 is treated like any other argument. Useful when input items might
50 contain white space, quote marks, or backslashes. The GNU find
51 \-print0 option produces input suitable for this mode.
52 .TP
53 .I "\-\-eof[=eof-str], \-e[eof-str]"
54 Set the end of file string to \fIeof-str\fR. If the end of file
55 string occurs as a line of input, the rest of the input is ignored.
56 If \fIeof-str\fR is omitted, there is no end of file string. If this
57 option is not given, the end of file string defaults to "_".
58 .TP
59 .I "\-\-help"
60 Print a summary of the options to
61 .B xargs
62 and exit.
63 .TP
64 .I "\-\-replace[=replace-str], \-i[replace-str]"
65 Replace occurences of \fIreplace-str\fR in the initial-arguments with
66 names read from standard input.
67 Also, unquoted blanks do not terminate input items.
68 If \fIreplace-str\fR is omitted, it
69 defaults to "{}" (like for `find \-exec'). Implies \fI\-x\fP and
70 \fI\-l 1\fP.
71 .TP
72 .I "\-\-max-lines[=max-lines], -l[max-lines]"
73 Use at most \fImax-lines\fR nonblank input lines per command line;
74 \fImax-lines\fR defaults to 1 if omitted. Trailing blanks cause an
75 input line to be logically continued on the next input line. Implies
76 \fI\-x\fR.
77 .TP
78 .I "\-\-max-args=max-args, \-n max-args"
79 Use at most \fImax-args\fR arguments per command line. Fewer than
80 \fImax-args\fR arguments will be used if the size (see the \-s option)
81 is exceeded, unless the \-x option is given, in which case \fBxargs\fR
82 will exit.
83 .TP
84 .I "\-\-interactive, \-p"
85 Prompt the user about whether to run each command line and read a line
86 from the terminal. Only run the command line if the response starts
87 with `y' or `Y'. Implies \fI\-t\fR.
88 .TP
89 .I "\-\-no-run-if-empty, \-r"
90 If the standard input does not contain any nonblanks, do not run the
91 command. Normally, the command is run once even if there is no input.
92 .TP
93 .I "\-\-max-chars=max-chars, \-s max-chars"
94 Use at most \fImax-chars\fR characters per command line, including the
95 command and initial-arguments and the terminating nulls at the ends of
96 the argument strings. The default is 20480 characters, not including
97 the size of the environment variables (which are provided for
98 separately so that it doesn't matter if your environment variables
99 take up more than 20480 bytes).
100 .TP
101 .I "\-\-verbose, \-t"
102 Print the command line on the standard error output before executing
103 it.
104 .TP
105 .I "\-\-version"
106 Print the version number of
107 .B xargs
108 and exit.
109 .TP
110 .I "\-\-exit, \-x"
111 Exit if the size (see the \fI\-s\fR option) is exceeded.
112 .TP
113 .I "\-\-max-procs=max-procs, \-P max-procs"
114 Run up to \fImax-procs\fR processes at a time; the default is 1. If
115 \fImax-procs\fR is 0, \fBxargs\fR will run as many processes as
116 possible at a time. Use the \fI\-n\fR option with \fI\-P\fR;
117 otherwise chances are that only one exec will be done.
118 .SH "EXAMPLES"
119 .nf
120 .B find /tmp -name core -type f -print | xargs /bin/rm -f
122 .fi
123 Find files named
124 .B core
125 in or below the directory
126 .B /tmp
127 and delete them. Note that this will work incorrectly if there are
128 any filenames containing newlines or spaces.
129 .P
130 .B find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f
132 .fi
133 Find files named
134 .B core
135 in or below the directory
136 .B /tmp
137 and delete them, processing filenames in such a way that file or
138 directory names containing spaces or newlines are correctly handled.
139 .P
140 .nf
141 .B cut -d: -f1 < /etc/passwd | sort | xargs echo
143 .fi
144 Generates a compact listing of all the users on the system.
145 .SH "EXIT STATUS"
146 .B xargs
147 exits with the following status:
148 .nf
149 0 if it succeeds
150 123 if any invocation of the command exited with status 1-125
151 124 if the command exited with status 255
152 125 if the command is killed by a signal
153 126 if the command cannot be run
154 127 if the command is not found
155 1 if some other error occurred.
156 .fi
157 .P
158 Exit codes greater than 128 are used by the shell to indicate that
159 a program died due to a fatal signal.
160 .SH "SEE ALSO"
161 \fBfind\fP(1), \fBlocate\fP(1), \fBlocatedb\fP(5), \fBupdatedb\fP(1),
162 \fBFinding Files\fP (on-line in Info, or printed)
163 .SH "BUGS"
164 .P
165 Some options exist in POSIX but are not yet implemented.
166 .P
167 When you use the \-i option, each line read from the input is buffered
168 internally. This means that there is an upper limit on the length
169 of input line that
170 .B xargs
171 will accept when used with the \-i option. To work around this
172 limitation, you can use the \-s option to increase the amount of
173 buffer space that
174 .B xargs
175 uses, and you can also use an extra invocation of
176 .B xargs
177 to ensure that very long lines do not occur.
178 For example:
179 .P
180 .B echo * | xargs -s 50000 echo | xargs -i -s 100000 rm '{}'
181 .P
182 Here, the first invocation of
183 .B xargs
184 has no input line length limit
185 because it doesn't use the \-i option. The second invocation of
186 .B xargs
187 does have such a limit, but we have ensured that the it never encounters
188 a line which is longer than it can handle. This is not an ideal
189 solution. Instead, the \-i option should not impose a line length
190 limit, which is why this discussion is listed in the BUGS section.
191 The problem doesn't occur with the output of
192 .BR find (1)
193 because it emits just one filename per line.
194 .P
195 The best way to report a bug is to use the form at
196 http://savannah.gnu.org/bugs/?group=findutils.
197 The reason for this is that you will then be able to track progress in
198 fixing the problem. Other comments about \fBxargs\fP(1) and about
199 the findutils package in general can be sent to the
200 .I bug-findutils
201 mailing list. To join the list, send email to
202 .IR bug-findutils-request@gnu.org .