execute a command as another user
|
list directory contents
|
-1 list one file per line
|
-d, --directory
list directory entries instead of contents, and do not dereference symbolic links
|
List information about the FILEs (the current directory by default). Sort entries alphabetically if none
of -cftuvSUX nor --sort is specified.
|
Pipelines
A pipeline is a sequence of one or more commands separated by one of the control operators | or |&. The
format for a pipeline is:
[time [-p]] [ ! ] command [ [|⎪|&] command2 ... ]
The standard output of command is connected via a pipe to the standard input of command2. This
connection is performed before any redirections specified by the command (see REDIRECTION below). If |&
is used, the standard error of command is connected to command2's standard input through the pipe; it is
shorthand for 2>&1 |. This implicit redirection of the standard error is performed after any
redirections specified by the command.
The return status of a pipeline is the exit status of the last command, unless the pipefail option is
enabled. If pipefail is enabled, the pipeline's return status is the value of the last (rightmost)
command to exit with a non-zero status, or zero if all commands exit successfully. If the reserved word
! precedes a pipeline, the exit status of that pipeline is the logical negation of the exit status as
described above. The shell waits for all commands in the pipeline to terminate before returning a value.
If the time reserved word precedes a pipeline, the elapsed as well as user and system time consumed by
its execution are reported when the pipeline terminates. The -p option changes the output format to that
specified by POSIX. When the shell is in posix mode, it does not recognize time as a reserved word if
the next token begins with a `-'. The TIMEFORMAT variable may be set to a format string that specifies
how the timing information should be displayed; see the description of TIMEFORMAT under Shell Variables
below.
When the shell is in posix mode, time may be followed by a newline. In this case, the shell displays the
total user and system time consumed by the shell and its children. The TIMEFORMAT variable may be used
to specify the format of the time information.
Each command in a pipeline is executed as a separate process (i.e., in a subshell).
|
construct argument lists and invoke utility
|
-I replstr
Insert mode: utility is executed for each line from standard input, taking the entire line as a
single argument, inserting it in arguments for each occurrence of replstr. A maximum of five
arguments in arguments can each contain one or more instances of replstr. Any <blank>s at the
beginning of each line shall be ignored. Constructed arguments cannot grow larger than 255 bytes.
Option -x shall be forced on.
|
-s size
Invoke utility using as many standard input arguments as possible yielding a command line length
less than size (a positive decimal integer) bytes. Fewer arguments shall be used if:
* The total number of arguments exceeds that specified by the -n option.
* The total number of lines exceeds that specified by the -L option.
* End-of-file is encountered on standard input before size bytes are accumulated.
Values of size up to at least {LINE_MAX} bytes shall be supported, provided that the constraints
specified in the DESCRIPTION are met. It shall not be considered an error if a value larger than that
supported by the implementation or exceeding the constraints specified in the DESCRIPTION is given; xargs
shall use the largest value it supports within the constraints.
|
AND and OR lists are sequences of one of more pipelines separated by the && and || control operators,
respectively. AND and OR lists are executed with left associativity. An AND list has the form
command1 && command2
command2 is executed if, and only if, command1 returns an exit status of zero.
An OR list has the form
command1 || command2
command2 is executed if and only if command1 returns a non-zero exit status. The return status of AND
and OR lists is the exit status of the last command executed in the list.
|