man xargs

NAME
       xargs - build and execute command lines from standard input

SYNOPSIS
       xargs  [-0prtx] [-E eof-str] [-e[eof-str]] [--eof[=eof-str]] [--null] [-d delimiter] [--delimiter delimiter] [-I replace-str] [-i[replace-str]]
       [--replace[=replace-str]]  [-l[max-lines]]  [-L  max-lines]  [--max-lines[=max-lines]]  [-n  max-args]  [--max-args=max-args]  [-s   max-chars]
       [--max-chars=max-chars]  [-P  max-procs]  [--max-procs=max-procs]  [--interactive]  [--verbose]  [--exit] [--no-run-if-empty] [--arg-file=file]
       [--version] [--help] [command [initial-arguments]]

DESCRIPTION
       This manual page documents the GNU version of xargs.  xargs reads items from the standard input, delimited by blanks (which  can  be  protected
       with  double  or single quotes or a backslash) or newlines, and executes the command (default is /bin/echo) one or more times with any initial-
       arguments followed by items read from standard input.  Blank lines on the standard input are ignored.

       Because Unix filenames can contain blanks and newlines, this default behaviour is often problematic; filenames containing  blanks  and/or  new-
       lines  are incorrectly processed by xargs.  In these situations it is better to use the '-0' option, which prevents such problems.   When using
       this option you will need to ensure that the program which produces the input for xargs also uses a null character as  a  separator.   If  that
       program is GNU find for example, the '-print0' option does this for you.
   说明下unix的文件名可以包含空格或者\n那么在用xargs的时候需要用-0选项来阻止这样的问题。另外在用该选项的时候必须保证stdin可以用一个空字符作为分隔符。如果是用GNU的find那么可以用-print0 来实现。
       If  any  invocation of the command exits with a status of 255, xargs will stop immediately without reading any further input.  An error message
       is issued on stderr when this happens.
如果任何一个命令的退出状态是255.xargs将会立即停止，不再处理任何输入。报错信息会在stderr上看到。
   OPTIONS
       --arg-file=file, -a file
              Read items from file instead of standard input.  If you use this option, stdin remains unchanged  when  commands  are  run.   Otherwise,
              stdin is redirected from /dev/null.
 -a file  读文件从file而不是标准是输入。
       --null, -0
              Input  items  are terminated by a null character instead of by whitespace, and the quotes and backslash are not special (every character
              is taken literally).  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.  The GNU find -print0 option produces input suitable for this mode.
-null,-0 输入是用一个null字符来代替空格，这个在输入的内容里包括空格，引用符，\的时候有用。另外GNU find可以用-print0 的输出来满足这个模式。
       --delimiter=delim, -d delim
              Input items are terminated by the specified character.  Quotes and backslash are not special; every character in the input is taken lit-
              erally.  Disables the end-of-file string, which is treated like any other argument.  This can be used 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.  The speci-
              fied delimiter may be a single character, a C-style character escape such as \n, or an octal or hexadecimal escape code.  Octal and hex-
              adecimal escape codes are understood as for the printf command.   Multibyte characters are not supported.
-d delim 分割输入用特定字符.
       -Eeof-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 nei-
              ther -E nor -e is used, no end of file string is used.

       --eof[=eof-str], -e[eof-str]
              This option is a synonym for the '-E' option.  Use '-E' instead, because it is POSIX compliant while this option is not.  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.

       --help Print a summary of the options to xargs and exit.

       -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　替换初始化参数
       --replace[=replace-str], -i[replace-str]
              This option is a synonym for -Ireplace-str if replace-str is specified, and for -I{} otherwise.   This  option  is  deprecated;  use  -I
              instead.

       -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 使用至多多少非空行。
       --max-lines[=max-lines], -l[max-lines]
              Synonym for the -L option.  Unlike -L, the max-lines argument is optional.  If max-args is not specified, it defaults to  one.   The  -l
              option is deprecated since the POSIX standard specifies -L instead.

       --max-args=max-args, -n max-args
              Use  at  most  max-args  arguments  per  command  line.   Fewer  than max-args arguments will be used if the size (see the -s option) is
              exceeded, unless the -x option is given, in which case xargs will exit.
-n max-args 每个命令使用至多多少个参数。
       --interactive, -p
              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.

       --no-run-if-empty, -r
              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.

       --max-chars=max-chars, -s max-chars
              Use at most max-chars characters per command line, including the command and initial-arguments and the terminating nulls at the ends  of
              the  argument  strings.   The  default is 131072 characters, not including the size of the environment variables (which are provided for
              separately so that it doesn't matter if your environment variables take up more than 131072 bytes).  The operating system places  limits
              on  the values that you can usefully specify, and if you exceed these a warning message is printed and the value actually used is set to
              the appropriate upper or lower limit.

       --verbose, -t
              Print the command line on the standard error output before executing it.
   -t 打印命令到标准错误。
       --version
              Print the version number of xargs and exit.

       --exit, -x
              Exit if the size (see the -s option) is exceeded.

       --max-procs=max-procs, -P max-procs
              Run up to max-procs processes at a time; the default is 1.  If max-procs is 0, xargs will run as many processes as possible at  a  time.
              Use the -n option with -P; otherwise chances are that only one exec will be done.

EXAMPLES
       find /tmp -name core -type f -print | xargs /bin/rm -f

       Find files named core in or below the directory /tmp and delete them.  Note that this will work incorrectly if there are any filenames contain-
       ing newlines or spaces.

       find /tmp -name core -type f -print0 | xargs -0 /bin/rm -f

       Find files named core in or below the directory /tmp and delete them, processing filenames in such a way that file or directory names  contain-
       ing spaces or newlines are correctly handled.

       cut -d: -f1 < /etc/passwd | sort | xargs echo

       Generates a compact listing of all the users on the system.

EXIT STATUS
       xargs exits with the following status:
       0 if it succeeds
       123 if any invocation of the command exited with status 1-125
       124 if the command exited with status 255
       125 if the command is killed by a signal
       126 if the command cannot be run
       127 if the command is not found
       1 if some other error occurred.

       Exit codes greater than 128 are used by the shell to indicate that a program died due to a fatal signal.

STANDARDS CONFORMANCE
       As  of  GNU xargs version 4.2.9, the default behaviour of xargs is not to have a logical end-of-file marker.  POSIX (IEEE Std 1003.1, 2004 Edi-
       tion) allows this.

       The -l and -i options appear in the 1997 version of the POSIX standard, but do not appear in the 2004 version of the standard.   Therefore  you
       should use -L and -I instead, respectively.

SEE ALSO
       find(1), locate(1), locatedb(5), updatedb(1), Finding Files (on-line in Info, or printed)

BUGS
       The -L option is incompatible with the -I option, but perhaps should not be.

       It  is  not possible for xargs to be used securely, since there will always be a time gap between the production of the list of input files and
       their use in the commands that xargs issues.  If other users have access to the system, they can manipulate the  filesystem  during  this  time
       window  to  force  the  action of the commands xargs runs to apply to files that you didn't intend.  For a more detailed discussion of this and
       related problems, please refer to the ''Security Considerations'' chapter in the findutils Texinfo documentation.  The -execdir option of  find
       can often be used as a more secure alternative.

       When  you  use  the -I option, each line read from the input is buffered internally.   This means that there is an upper limit on the length of
       input line that xargs will accept when used with the -I option.  To work around this limitation, you can use the  -s  option  to  increase  the
       amount  of  buffer  space  that xargs uses, and you can also use an extra invocation of xargs to ensure that very long lines do not occur.  For
       example:

       somecommand | xargs -s 50000 echo | xargs -I '{}' -s 100000 rm '{}'

       Here, the first invocation of xargs has no input line length limit because it doesn't use the -i option.  The second invocation of  xargs  does
       have such a limit, but we have ensured that the it never encounters a line which is longer than it can handle.   This is not an ideal solution.
       Instead, the -i option should not impose a line length limit, which is why this discussion appears in the BUGS section.   The  problem  doesn't
       occur with the output of find(1) because it emits just one filename per line.

       The best way to report a bug is to use the form at The reason for this is that you will then be
       able to track progress in fixing the problem.   Other comments about xargs(1) and about the findutils package in general can  be  sent  to  the
       bug-findutils mailing list.  To join the list, send email to [e-mail].