xargs(1)xargs(1)Namexargs - construct argument list and execute command
Syntaxxargs [flags] [ command [initial-arguments] ]
Description
The command combines fixed initial-arguments with arguments read from
standard input to execute a specified command one or more times. The
number of arguments read when a command is invoked and how they are
combined is determined by the options specified.
The specified command, (which can be a Shell file) is searched for
using ones' $PATH specification. If command is not specified,
/bin/echo is used.
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.
Options
Each argument list begins with the initial-arguments, followed by argu‐
ments read from standard input, with the exception of the -i option.
See the description of the -i option for more information.
The options -i, -l, and -n determine how arguments are selected when
each command is invoked. If none of these options are specified, the
initial-arguments are followed by arguments read continuously from
standard input until the internal buffer is full; then, command exe‐
cutes with the accumulated arguments. This process repeats until no
arguments exist. When conflicts arise, such as the -l option used with
the -n, the last option has precedence. The options values are as fol‐
lows:
-lnumber
Execute command for each non-empty 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 number
remain. A line ends with the first newline unless the last char‐
acter of the line is a blank or a tab; a trailing blank or tab
signals continuation through the next non-empty line. If number
is is not specified, the value 1 is assumed. The option -x is
forced.
-ireplstr (Insert mode)
Execute command for each line from standard input, taking the
entire line as a single argument and inserting it in initial-
arguments for each occurrence of replstr. A maximum of five
arguments specified in initial-arguments can contain one or more
occurrence of replstr. Blanks and tabs at the beginning of each
line are discarded. A constructed arguments cannot exceed 255
characters and the option -x is a forced. A {|} is assumed for
replstr if not specified.
-nnumber
Execute command using as many standard input arguments as possi‐
ble, up to the specified number arguments maximum. Fewer argu‐
ments are used if their total size is greater than size charac‐
ters, and when the last command is invoked, fewer number of argu‐
ments remain. If the option -x is also include, each specified
number of arguments must fit in the size limitation, or else
xargs terminates execution.
-t (Trace mode)
Echo the command and each constructed argument list to file
descriptor 2 prior to their execution.
-p (Prompt mode)
Asks the user whether or not command should be executed each time
command is invoked. Trace mode (-t) is turned on to print the
command instance to be executed, followed by a ?... prompt. A
reply of y executes the command; any other response does not
invoke that particular command.
-x Causes the command xargs to terminate if an argument list is
greater than the specified size of characters; the option -x is
forced by the options -i and -l. When the options -i, -l, or -n
are included, the total length of all arguments must be within
the specified size limit.
-ssize
The maximum size of each argument list is set to size characters;
size must be a positive integer less than or equal to 470. If -s
is not included, 470 is the default. Note that the character
count for size includes one extra character for each argument and
the count of characters in the command name.
-eeofstr
The option eofstr is taken as the logical end-of-file string.
Underscore (_) is assumed for the logical EOF string if -e is not
specified. The value -e without eofstr specified turns off the
logical EOF string capability; the underscore is taken literally.
The command xargs reads standard input until either end-of-file
or the logical EOF string is encountered.
The command xargs terminates if it receives a return code of -1 from
command or if it cannot execute command. When command is a Shell pro‐
gram, it should explicitly exit with an appropriate value to avoid
returning with -1. See for more information.
Examples
The following example moves all files from directory $1 to directory $2
and echoes the move command prior to executing it:
ls $1 | xargs-i -t mv $1/{} $2/{}
The following example combines the output of the parenthesized commands
onto one line, which is then echoed to the end of file log:
(logname; date; echo $0 $∗) | xargs >>log
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:
ls | xargs-p -l ar r arch
ls | xargs-p -l | xargs ar r arch
The following example executes diff(1) with successive pairs of argu‐
ments originally typed as Shell arguments:
echo $∗ | xargs-n2 diff
See Alsosh(1).
xargs(1)
