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1 .\" Copyright (c) 1990, 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
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4 .\" This code is derived from software contributed to Berkeley by
5 .\" John B. Roll Jr. and the Institute of Electrical and Electronics
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36 .\" @(#)xargs.1 8.1 (Berkeley) 6/6/93
37 .\" $FreeBSD: src/usr.bin/xargs/xargs.1,v 1.6.2.12 2003/06/01 21:40:35 mux Exp $
38 .\" $DragonFly: src/usr.bin/xargs/xargs.1,v 1.6 2007/09/02 19:30:47 swildner Exp $
39 .\" $xMach: xargs.1,v 1.2 2002/02/23 05:23:37 tim Exp $
40 .\"
41 .Dd May 7, 2001
42 .Dt XARGS 1
43 .Os
44 .Sh NAME
45 .Nm xargs
46 .Nd "construct argument list(s) and execute utility"
47 .Sh SYNOPSIS
48 .Nm
49 .Op Fl 0opt
50 .Op Fl E Ar eofstr
51 .Oo
52 .Fl I Ar replstr
53 .Op Fl R Ar replacements
54 .Oc
55 .Op Fl J Ar replstr
56 .Op Fl L Ar number
57 .Oo
58 .Fl n Ar number
59 .Op Fl x
60 .Oc
61 .Op Fl s Ar size
62 .Op Ar utility Op Ar argument ...
63 .Sh DESCRIPTION
64 The
65 .Nm
66 utility reads space, tab, newline and end-of-file delimited strings
67 from the standard input and executes
68 .Ar utility
69 with the strings as
70 arguments.
71 .Pp
72 Any arguments specified on the command line are given to
73 .Ar utility
74 upon each invocation, followed by some number of the arguments read
75 from the standard input of
76 .Nm .
77 The utility
78 is repeatedly executed until standard input is exhausted.
79 .Pp
80 Spaces, tabs and newlines may be embedded in arguments using single
81 (``\ '\ '')
82 or double (``"'') quotes or backslashes (``\e'').
83 Single quotes escape all non-single quote characters, excluding newlines,
84 up to the matching single quote.
85 Double quotes escape all non-double quote characters, excluding newlines,
86 up to the matching double quote.
87 Any single character, including newlines, may be escaped by a backslash.
88 .Pp
89 The options are as follows:
90 .Bl -tag -width indent
91 .It Fl 0
92 Change
93 .Nm
94 to expect NUL
95 (``\\0'')
96 characters as separators, instead of spaces and newlines.
97 This is expected to be used in concert with the
98 .Fl print0
99 function in
100 .Xr find 1 .
101 .It Fl E Ar eofstr
102 Use
103 .Ar eofstr
104 as a logical EOF marker.
105 .It Fl I Ar replstr
106 Execute
107 .Ar utility
108 for each input line, replacing one or more occurrences of
109 .Ar replstr
110 in up to
111 .Ar replacements
112 (or 5 if no
113 .Fl R
114 flag is specified) arguments to
115 .Ar utility
116 with the entire line of input.
117 The resulting arguments, after replacement is done, will not be allowed to grow
118 beyond 255 bytes; this is implemented by concatenating as much of the argument
119 containing
120 .Ar replstr
121 as possible, to the constructed arguments to
122 .Ar utility ,
123 up to 255 bytes.
124 The 255 byte limit does not apply to arguments to
125 .Ar utility
126 which do not contain
127 .Ar replstr ,
128 and furthermore, no replacement will be done on
129 .Ar utility
130 itself.
131 Implies
132 .Fl x .
133 .It Fl J Ar replstr
134 If this option is specified,
135 .Nm
136 will use the data read from standard input to replace the first occurrence of
137 .Ar replstr
138 instead of appending that data after all other arguments.
139 This option will not affect how many arguments will be read from input
140 .Pq Fl n ,
141 or the size of the command(s)
142 .Nm
143 will generate
144 .Pq Fl s .
145 The option just moves where those arguments will be placed in the command(s)
146 that are executed.
147 The
148 .Ar replstr
149 must show up as a distinct
150 .Ar argument
151 to
152 .Nm .
153 It will not be recognized if, for instance, it is in the middle of a
154 quoted string.
155 Furthermore, only the first occurrence of the
156 .Ar replstr
157 will be replaced.
158 For example, the following command will copy the list of files and
159 directories which start with an uppercase letter in the current
160 directory to
161 .Pa destdir :
162 .Pp
163 .Dl /bin/ls -1d [A-Z]* | xargs -J % cp -rp % destdir
164 .Pp
165 .It Fl L Ar number
166 Call
167 .Ar utility
168 for every
169 .Ar number
170 lines read.
171 If EOF is reached and fewer lines have been read than
172 .Ar number
173 then
174 .Ar utility
175 will be called with the available lines.
176 .It Fl n Ar number
177 Set the maximum number of arguments taken from standard input for each
178 invocation of
179 .Ar utility .
180 An invocation of
181 .Ar utility
182 will use less than
183 .Ar number
184 standard input arguments if the number of bytes accumulated (see the
185 .Fl s
186 option) exceeds the specified
187 .Ar size
188 or there are fewer than
189 .Ar number
190 arguments remaining for the last invocation of
191 .Ar utility .
192 The current default value for
193 .Ar number
194 is 5000.
195 .It Fl o
196 Reopen stdin as
197 .Pa /dev/tty
198 in the child process before executing the command.
199 This is useful if you want
200 .Nm
201 to run an interactive application.
202 .It Fl p
203 Echo each command to be executed and ask the user whether it should be
204 executed.
205 An affirmative response,
206 .Ql y
207 in the POSIX locale,
208 causes the command to be executed, any other response causes it to be
209 skipped.
210 No commands are executed if the process is not attached to a terminal.
211 .It Fl R Ar replacements
212 Specify the maximum number of arguments that
213 .Fl I
214 will do replacement in.
215 .It Fl s Ar size
216 Set the maximum number of bytes for the command line length provided to
217 .Ar utility .
218 The sum of the length of the utility name, the arguments passed to
219 .Ar utility
220 (including
221 .Dv NULL
222 terminators) and the current environment will be less than or equal to
223 this number.
224 The current default value for
225 .Ar size
226 is
227 .Dv ARG_MAX
228 - 4096.
229 .It Fl t
230 Echo the command to be executed to standard error immediately before it
231 is executed.
232 .It Fl x
233 Force
234 .Nm
235 to terminate immediately if a command line containing
236 .Ar number
237 arguments will not fit in the specified (or default) command line length.
238 .El
239 .Pp
240 If
241 .Ar utility
242 is omitted,
243 .Xr echo 1
244 is used.
245 .Pp
246 Undefined behavior may occur if
247 .Ar utility
248 reads from the standard input.
249 .Pp
250 The
251 .Nm
252 utility exits immediately (without processing any further input) if a
253 command line cannot be assembled,
254 .Ar utility
255 cannot be invoked, an invocation of
256 .Ar utility
257 is terminated by a signal,
258 or an invocation of
259 .Ar utility
260 exits with a value of 255.
261 .Sh DIAGNOSTICS
262 The
263 .Nm
264 utility exits with a value of 0 if no error occurs.
265 If
266 .Ar utility
267 cannot be found,
268 .Nm
269 exits with a value of 127, otherwise if
270 .Ar utility
271 cannot be executed,
272 .Nm
273 exits with a value of 126.
274 If any other error occurs,
275 .Nm
276 exits with a value of 1.
277 .Sh SEE ALSO
278 .Xr echo 1 ,
279 .Xr find 1 ,
280 .Xr execvp 3
281 .Sh STANDARDS
282 The
283 .Nm
284 utility is expected to be
285 .St -p1003.2
286 compliant.
287 The
288 .Fl J , o
289 and
290 .Fl R
291 options are non-standard
292 .Dx
293 extensions which may not be available on other operating systems.
294 .Sh HISTORY
295 The
296 .Nm
297 command appeared in PWB
298 .Ux .
299 .Sh BUGS
300 If
301 .Ar utility
302 attempts to invoke another command such that the number of arguments or the
303 size of the environment is increased, it risks
304 .Xr execvp 3
305 failing with
306 .Er E2BIG .