Pipelines

pipelines

Pipelines
       A pipeline is a sequence of one or more commands separated by the character |.  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).

       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 com-
       mands 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 termi-
       nates.   The -p option changes the output format to that specified by POSIX.  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.

       Each command in a pipeline is executed as a separate process (i.e., in a subshell).