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Shell command: xargs

xargs [options] [cmd [init-args]]
xargs reads {items} from stdin and executes cmd [init-args] {items}.
If cmd is omitted, xargs executes /bin/echo.
The items that xargs reads are delimited by blanks.
In order to pass an item that contains a blank, it can be put in quotes ("this is ONE item" or 'this would be ONE item, too') or the blank can be escaped with a backslash (`this\ is\ also\ an\ item').
cmd will be executed multiple times if the length including the items exceeds a certain limit (unless -n or -L are involved).

Options

-0 --null Input items are terminated by a NUL character instead of by whitespace. Quotes and backslash are not special. Disables the end of file string, which is treated like any other argument. Useful when input items might contain white space, quote marks, or backslashes. (GNU find -print0 option produces input suitable for this mode).
-a --arg-file= file Read items from file instead of stdin. With this option, stdin remains unchanged when commands are run. Otherwise, stdin is redirected from /dev/null.
-d --delimiter= delim Input items are terminated by the specified character, escaped characters such as \n or an octal or hexadecimal escape code. Octal and hexadecimal escape codes are understood as for the printf command. Multibyte characters are not supported. When processing the input, quotes and backslash are not special; every character in the input is taken literally. The -d option disables any end-of-file string, which is treated like any other argument. You can use this option when the input consists of simply newline-separated items, although it is almost always better to design your program to use --null where this is possible.
-E eof-str Set the end of file string to eof-str. If the end of file string occurs as a line of input, the rest of the input is ignored. If neither -E nor -e is used, no end of file string is used.
-e --eof eof-str This option is non-POSIX complianta synonym for the -E option. If eof-str is omitted, there is no end of file string. If neither -E nor -e is used, no end of file string is used.
-I replace-str Replace occurrences of replace-str in the initial-arguments with names read from standard input. Also, unquoted blanks do not terminate input items; instead the separator is the newline character. Implies -x and -L 1.
-i[replace-str] --replace[=replace-str] This option is a synonym for -Ireplace-str if replace-str is specified. If the replace-str argument is missing, the effect is the same as -I{}. This option is deprecated in favor of -I.
-L max-lines Use at most max-lines nonblank input lines per command line. Trailing blanks cause an input line to be logically continued on the next input line. Implies -x.
-l[max-lines] --max-lines[=max-lines] deprecated synonym for -L. Unlike -L, the max-lines argument is optional. If max-lines is not specified, it defaults to one.
-n --max-args= max-args Use at most max-args arguments per command line.
-P --max-procs= max-procs Run up to max-procs processes at a time (default = 1). -P 0 will run as many processes as possible at a time. Should probably be used with -n or -L.
-o --open-tty Reopen stdin as /dev/tty in the child process before executing the command. Useful to run interactive applications.
-p --interactive Prompt the user about whether to run each command line and read a line from the terminal. Only run the command line if the response starts with y' or Y'. Implies -t.
--process-slot-var= name Set the environment variable name to a unique value in each running child process. Values are reused once child processes exit. This can be used in a rudimentary load distribution scheme, for example.
-r --no-run-if-empty If the standard input does not contain any nonblanks, do not run the command. Normally, the command is run once even if there is no input. This option is a GNU extension.
-s --max-chars= max-chars Use at most max-chars characters per command line.
--show-limits Display the limits on the command-line length which are imposed by the operating system, xargs' choice of buffer size and the -s option. Pipe the input from /dev/null (and perhaps specify --no-run-if-empty) if you don't want xargs to do anything.
-t --verbose Print the command line on the standard error output before executing it.
-x --exit Exit if the size (see the -s option) is exceeded.
--help Print a summary of the options to xargs and exit.
--version Print the version number of xargs and exit.
The options --max-lines (-L, -l), --replace (-I, -i) and --max-args (-n) are mutually exclusive.
The special max-args value 1 (-n1) is ignored after the --replace option and its aliases -I and -i because it would not actually conflict.

Simple example

Create a (empty) file: 
$ touch a.file
Pipe the words a.file and renamed.file to xargs mv (which will build and execute the command mv a.file renamed.file): 
$ echo a.file renamed.file | xargs mv
Verify that a.file was renamed to renamed.file: 
$ ls -ltr

-I

$ mkdir /tmp/xargs-I-demo
$ cd    /tmp/xargs-I-demo

$ echo one   > 1.txt
$ echo two   > 2.txt
$ echo three > 3.txt

$ ls -1 | xargs -IFILENAME cat FILENAME
one
two
three
Note: when using -I, the read items are delimited by a new line, not a space. 
$ echo {1..3}.txt | xargs -IFILENAME cat FILENAME
cat: '1.txt 2.txt 3.txt': No such file or directory

$ echo {1..3}.txt | xargs -n1 | xargs -IFILENAME cat FILENAME
one
two
three

TODO

echo -e 'foo bar baz\x00one two three' | xargs -0 -t -n 1 echo
echo -e '"foo bar baz" hello\ world  xyz' | xargs  -t -n 1 echo

See also

xargs is often used in conjunction with find … -exec xargs {} + …
Using xargs and grep to find files that match multiple regular expressions.
Shell commands
Emulating xargs in PowerShell.

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