xargs.1

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.TH xargs 1
.SH Name
xargs \- construct argument list and execute command 
.SH Syntax
.NXR "xargs command"
.B xargs
[\fIflags\fR] [ \fIcommand\fR [\fIinitial-arguments\fR] ]
.SH Description
The command
.PN xargs
combines fixed
.I initial-arguments
with arguments read from standard input to execute a specified
.I command
one or more times.  The number of arguments read when a 
.I command
is invoked and how they are combined
is determined by the options specified.
.PP
The specified
.I command,
(which can be a Shell file)
is searched for using ones' \fB$PATH\fR specification.
If
.I command
is not specified,
.B /bin/echo
is used.
.PP
Arguments read from standard input are defined as contiguous
strings of characters delimited by one or more blanks, tabs, or newlines;
empty lines are always discarded.
Blanks and tabs can be embedded as part of an argument if they contain
an escape character or if they are quoted.
Characters enclosed in quotes (single or double) are taken literally,
and the delimiting quotes are removed; a backslash (\\)
escapes the next character.
.SH Options
Each argument list begins with the
.IR initial-arguments,
followed by arguments read from standard input, with the exception
of the 
.B \-i
option.  See the description of the 
.BR \-i 
option for more information.
.PP
The options
.BR \-i ,
.BR \-l ,
and
.BR \-n
determine how arguments are selected when each command is invoked.
If none of these options are specified, the
.I initial-arguments
are followed by arguments read continuously from standard input until 
the internal buffer is full; then,
.I command
executes with the accumulated arguments.  This process repeats
until no arguments exist.  When conflicts arise, such
as the 
.B \-l
option used with the
.BR \-n,
the last option has precedence. The options values are as follows:
.TP 6
.BI \-l number
Execute 
.I command 
for each non-empty
.I number
lines of arguments from standard input.
When command is invoked for the final time, 
it has fewer lines of arguments if fewer than a specified
.I number
remain.
A line ends with the first newline unless
the last character of the line is a blank or a tab;
a trailing blank or tab signals continuation through the next non-empty line.
If
.I number
is is not specified, the value 1 is assumed.
The option
.B \-x
is forced.
.TP 6
\fB\-i\fR\fIreplstr\fR \fB(Insert mode)\fR
Execute
.I command
for each line from standard input,
taking the entire line as a single argument and inserting it in
.I initial-arguments\^
for each occurrence of
.IR replstr .
A maximum of five arguments specified in 
.I initial-arguments
can contain one or more occurrence of
.IR replstr .
Blanks and tabs at the beginning of each line are discarded.
A constructed arguments cannot exceed 255 characters and the option
.B \-x
is a forced.
A 
.B {|}
is assumed for
.I replstr
if not specified.
.TP 6
.BI \-n number
Execute
.I command
using as many standard input arguments as possible, up to the specified
.I number
arguments maximum.
Fewer arguments are used if their total size is greater than
.I size
characters, and when the last command is invoked, fewer
.I number
of arguments remain.
If the option
.B \-x
is also include, each specified
.I number
of arguments must fit in the
.I size
limitation, or else
.I xargs
terminates execution.
.TP 6
.B \-t (Trace mode)
Echo the
.I command\^
and each constructed argument list to file descriptor 2
prior to their execution.
.TP 6
.B \-p (Prompt mode)
Asks the user whether or not 
.I command\^
should be executed each time 
.I command
is invoked. Trace mode (\c
.B \-t\c
) is turned on to print the command instance to be executed,
followed by a \fB?.\|.\|.\fP prompt.
A reply of
.B y
executes the command; any other response
does not invoke that particular
.IR command.
.TP 6
.B \-x
Causes the command
.I xargs
to terminate if an argument list is greater than the specified
.I size
of characters; the option
.B \-x
is forced by the options
.B \-i
and
.BR \-l .
When the options
.BR \-i ,
.BR \-l ,
or
.B \-n
are included, the total length of all arguments must be within the specified
.I size
limit.
.TP 6
.BI \-s size
The maximum size of each argument list is set to
.I size
characters;
.I size
must be a positive integer less than or equal to 470. If
.B \-s
is not included, 470 is the default.
Note that the character count for
.I size
includes one extra character for each argument and the count of characters 
in the command name.
.TP 6
.BI \-e eofstr
The option
.I eofstr
is taken as the logical end-of-file string.
Underscore (\|_\|) is assumed for
the logical \fB\s-1EOF\s+1\fR string
if \fB\-e\fR is not specified.
The value
\fB\-e\fR without
.I eofstr
specified turns off the logical \fB\s-1EOF\s+1\fP string capability;
the underscore is taken literally.
The command
.I xargs
reads standard input until either end-of-file or the logical 
\fB\s-1EOF\s+1\fP string is encountered.
.PP
The command
.I xargs
terminates if it receives a return code of
.B \-1
from 
.IR command 
or if it cannot execute
.IR command .
When
.I command
is a Shell program, it should explicitly
.I exit
with an appropriate value to avoid returning with
.BR \-1 .
See 
.MS sh 1
for more information.
.SH Examples
The following example moves all files from directory $1 to directory $2
and echoes the move command prior to executing it:
.PP
ls \|$1 \|| \|xargs \|\-i \|\-t \|mv \|$1/{\|} \|$2/{\|}
.PP
The following example combines the output of the parenthesized commands 
onto one line, which is then echoed to the end of file \fIlog\fP:
.PP
(logname; \|date; \|echo \|$0 \|$\(**) \|| \|xargs \|>>log
.PP
In the next example, the user is prompted to specify which files in the
current directory are to be archived.  The first example archives the
files one at a time; the second example archives groups of files:
.PP
\ \|\ \|ls \|| \|xargs \|\-p \|\-l \|ar \|r \|arch
.sp
\ \|\ \|ls \|| \|xargs \|\-p \|\-l \|| \|xargs \|ar \|r \|arch
.PP
The following example executes
.IR diff "(1)"
with successive
pairs of arguments originally typed as Shell arguments:
.PP
echo \|$\(** \|| \|xargs \|\-n2 \|diff
.SH See Also
sh(1).