xargs(1) xargs(1)NAME xargs - construct argument list and execute command SYNOPSIS xargs [flags] [command [initial-arguments]] DESCRIPTION xargs combines the fixed initial-arguments with arguments read from standard input to execute the specified command one or more times. The number of arguments read for each command invocation and the manner in which they are combined are determined by the flags specified. command, which may be a shell file, is searched for, using one's $PATH. If command is omitted, /bin/echo is used. Arguments read in from standard input are defined to be con- tiguous strings of characters delimited by one or more blanks, tabs, or newlines; empty lines are always discarded. Blanks and tabs may be embedded as part of an argument if escaped or quoted. Characters enclosed in quotes (single or double) are taken literally, and the delimiting quotes are removed. Outside of quoted strings, a backslash (\) will escape the next character. Each argument list is constructed starting with the initial-arguments, followed by some number of arguments read from standard input (Exception: see -i flag option). Flag options -i, -l, and -n determine how arguments are selected for each command invocation. When none of these flag op- tions are coded, the initial-arguments are followed by argu- ments read continuously from standard input until an inter- nal buffer is full, and then command is executed with the accumulated arguments. This process is repeated until there are no more arguments. When there are flag option conflicts (for example, -l versus -n), the last flag option has pre- cedence. Flag option values are: -lnumber command is executed for each nonempty number lines of arguments from standard input. The last invocation of command will be with fewer lines of arguments if fewer than number remain. A line is considered to end with the first new- line unless the last character of the line is a blank or a tab; a trailing blank/tab signals continuation through the next nonempty line. If number is omitted, 1 is assumed. Flag option -x is forced. -ireplstr Insert mode: command is executed for each line from standard input, taking the entire line as a single argument, inserting it in initial- April, 1990 1
xargs(1) xargs(1)arguments for each occurrence of replstr. A maximum of 5 arguments in initial-arguments may each contain one or more instances of replstr. Blanks and tabs at the beginning of each line are thrown away. Constructed arguments may not grow larger than 255 characters, and flag option -x is also forced. {} is assumed for replstr if not specified. -nnumber Execute command using as many standard input ar- guments as possible, up to number arguments max- imum. Fewer arguments will be used if their to- tal size is greater than size characters, and for the last invocation if there are fewer than number arguments remaining. If flag option -x is also coded, each number arguments must fit in the size limitation, else xargs terminates exe- cution. -t Trace mode: The command and each constructed ar- gument list are echoed to file descriptor 2 just prior to their execution. -p Prompt mode: The user is asked whether to exe- cute command at each invocation. Trace mode (- t) is turned on to print the command instance to be executed, followed by a ?... prompt. A re- ply of y (optionally followed by anything) will execute the command; anything else, including just a carriage return, skips that particular invocation of command. -x Causes xargs to terminate if any argument list would be greater than size characters; -x is forced by the flag options -i and -l. When none of the flag options -i, -l, or -n are coded, the total length of all arguments must be within the size limit. -ssize The maximum total 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 coded, 470 is taken as 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 eofstr is taken as the logical end-of-file string. Underbar (_) is assumed for the logical EOF string if -e is not coded. The value -e with no eofstr coded turns off the logical EOF string capability (underbar is taken literally). 2 April, 1990
xargs(1) xargs(1)xargs reads standard input until either end-of- file or the logical EOF string is encountered. xargs will terminate if either: it cannot execute command command returns a -1 exit status. When command is a shell program, it should explicitly exit (see sh(1)) with an appropriate value to avoid accidentally returning with -1 . EXAMPLES ls $1 | xargs -i -t mv $1/{} $2/{} will move all files from directory $1 to directory $2, and echo each move command just before doing it. (logname; date; echo $0 $*) | xargs >>log will combine the output of the parenthesized commands onto one line, which is then echoed to the end of file log. ls | xargs -p -l ar r arch ls | xargs -p -l | xargs ar r arch causes the user to be asked which files in the current directory are to be archived and archives them into arch one at a time in the first instance, or as in the second in- stance, many at a time. echo $* | xargs -n2 diff will execute diff(1) with successive pairs of arguments ori- ginally typed as shell arguments. FILES /usr/bin/xargs SEE ALSO csh(1), ksh(1), sh(1). April, 1990 3