xref: /freebsd/usr.bin/xargs/xargs.1 (revision 71fe318b852b8dfb3e799cb12ef184750f7f8eac)
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36.\"	@(#)xargs.1	8.1 (Berkeley) 6/6/93
37.\" $FreeBSD$
38.\" $xMach: xargs.1,v 1.2 2002/02/23 05:23:37 tim Exp $
39.\"
40.Dd May 7, 2001
41.Dt XARGS 1
42.Os
43.Sh NAME
44.Nm xargs
45.Nd "construct argument list(s) and execute utility"
46.Sh SYNOPSIS
47.Nm
48.Op Fl 0pt
49.Op Fl E Ar eofstr
50.Oo
51.Fl I Ar replstr
52.Op Fl R Ar replacements
53.Oc
54.Op Fl J Ar replstr
55.Op Fl L Ar number
56.Oo
57.Fl n Ar number
58.Op Fl x
59.Oc
60.Op Fl s Ar size
61.Op Ar utility Op Ar argument ...
62.Sh DESCRIPTION
63The
64.Nm
65utility reads space, tab, newline and end-of-file delimited arguments
66from the standard input and executes the specified
67.Ar utility
68with them as
69arguments.
70.Pp
71The utility and any arguments specified on the command line are given
72to the
73.Ar utility
74upon each invocation, followed by some number of the arguments read
75from standard input.
76The
77.Ar utility
78is repeatedly executed until standard input is exhausted.
79.Pp
80Spaces, tabs and newlines may be embedded in arguments using single
81(``\ '\ '')
82or double (``"'') quotes or backslashes (``\e'').
83Single quotes escape all non-single quote characters, excluding newlines,
84up to the matching single quote.
85Double quotes escape all non-double quote characters, excluding newlines,
86up to the matching double quote.
87Any single character, including newlines, may be escaped by a backslash.
88.Pp
89The options are as follows:
90.Bl -tag -width indent
91.It Fl 0
92Change
93.Nm
94to expect NUL
95(``\\0'')
96characters as separators, instead of spaces and newlines.
97This is expected to be used in concert with the
98.Fl print0
99function in
100.Xr find 1 .
101.It Fl E Ar eofstr
102Use
103.Ar eofstr
104as a logical EOF marker.
105.It Fl I Ar replstr
106Execute
107.Ar utility
108for each input line, replacing one or more occurences of
109.Ar replstr
110in up to
111.Ar replacements
112(or 5 if no
113.Fl R
114flag is specified) arguments to
115.Ar utility
116with the entire line of input.
117The resulting arguments, after replacement is done, will not be allowed to grow
118beyond 255 bytes; this is implemented by concatenating as much of the argument
119containing
120.Ar replstr
121as possible, to the constructed arguments to
122.Ar utility ,
123up to 255 bytes.
124The 255 byte limit does not apply to arguments to
125.Ar utility
126which do not contain
127.Ar replstr ,
128and furthermore, no replacement will be done on
129.Ar utility
130itself.
131Implies
132.Fl x .
133.It Fl J Ar replstr
134If this option is specified,
135.Nm
136will use the data read from standard input to replace the first occurrence of
137.Ar replstr
138instead of appending that data after all other arguments.
139This option will not effect how many arguments will be read from input
140.Pq Fl n ,
141or the size of the command(s)
142.Nm
143will generate
144.Pq Fl s .
145The option just moves where those arguments will be placed in the command(s)
146that are executed.
147The
148.Ar replstr
149must show up as a distinct
150.Ar argument
151to
152.Nm .
153It will not be recognized if, for instance, it is in the middle of a
154quoted string.
155Furthermore, only the first occurrence of the
156.Ar replstr
157will be replaced.
158For example, the following command will copy the list of files and
159directories which start with an uppercase letter in the current
160directory 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
166Call
167.Ar utility
168for every
169.Ar number
170lines read.
171If EOF is reached and fewer lines have been read than
172.Ar number
173then
174.Ar utility
175will be called with the available lines.
176.It Fl n Ar number
177Set the maximum number of arguments taken from standard input for each
178invocation of the utility.
179An invocation of
180.Ar utility
181will use less than
182.Ar number
183standard input arguments if the number of bytes accumulated (see the
184.Fl s
185option) exceeds the specified
186.Ar size
187or there are fewer than
188.Ar number
189arguments remaining for the last invocation of
190.Ar utility .
191The current default value for
192.Ar number
193is 5000.
194.It Fl p
195Echo each command to be executed and ask the user whether it should be
196executed.
197An affirmative response,
198.Ql y
199in the POSIX locale,
200causes the command to be executed, any other response causes it to be
201skipped.
202No commands are executed if the process is not attached to a terminal.
203.It Fl R Ar replacements
204Specify the maximum number of arguments that
205.Fl I
206will do replacement in.
207.It Fl s Ar size
208Set the maximum number of bytes for the command line length provided to
209.Ar utility .
210The sum of the length of the utility name, the arguments passed to
211.Ar utility
212(including
213.Dv NULL
214terminators) and the current environment will be less than or equal to
215this number.
216The current default value for
217.Ar size
218is
219.Dv ARG_MAX
220- 4096.
221.It Fl t
222Echo the command to be executed to standard error immediately before it
223is executed.
224.It Fl x
225Force
226.Nm
227to terminate immediately if a command line containing
228.Ar number
229arguments will not fit in the specified (or default) command line length.
230.El
231.Pp
232If no
233.Ar utility
234is specified,
235.Xr echo 1
236is used.
237.Pp
238Undefined behavior may occur if
239.Ar utility
240reads from the standard input.
241.Pp
242The
243.Nm
244utility exits immediately (without processing any further input) if a
245command line cannot be assembled,
246.Ar utility
247cannot be invoked, an invocation of the utility is terminated by a signal
248or an invocation of the utility exits with a value of 255.
249.Sh DIAGNOSTICS
250The
251.Nm
252utility exits with a value of 0 if no error occurs.
253If
254.Ar utility
255cannot be found,
256.Nm
257exits with a value of 127, otherwise if
258.Ar utility
259cannot be executed,
260.Nm
261exits with a value of 126.
262If any other error occurs,
263.Nm
264exits with a value of 1.
265.Sh SEE ALSO
266.Xr echo 1 ,
267.Xr find 1 ,
268.Xr execvp 3
269.Sh STANDARDS
270The
271.Nm
272utility is expected to be
273.St -p1003.2
274compliant.
275The
276.Fl J
277and
278.Fl R
279options are non-standard
280.Fx
281extensions which may not be available on other operating systems.
282.Sh HISTORY
283The
284.Nm
285command appeared in PWB UNIX.
286.Sh BUGS
287If
288.Ar utility
289attempts to invoke another command such that the number of arguments or the
290size of the environment is increased, it risks
291.Xr execvp 3
292failing with
293.Er E2BIG .
294