Wednesday, May 23, 2012

Zsh: merge stdout and stderr with |&

|& provides a zsh-only shortcut for merging STDOUT and STDERR when piping. It is the same as 2>&1 | , just a lot shorter to type. I find this useful for commands that feel like dumping --help output to STDERR.

command --help |& less

Pro Tip: Don't confuse this with &| which backgrounds the final command of the pipeline.

Find out more in the "Simple commands & pipelines" section of zshmisc:

A pipeline is either a simple command, or a sequence of two or more simple commands where each command is separated from the next by `|' or `|&'. Where commands are separated by `|', the standard output of the first command is connected to the standard input of the next. `|&' is shorthand for `2>&1 |', which connects both the standard output and the standard error of the command to the standard input of the next.

Update: |& is borrowed from csh. I don't know if it originated in csh or prior.

The standard error output may be directed through a pipe with the standard output. Simply use the form |& instead of just |.

-- man csh(1)

1 comment:

Tommy Stanton said...

Wow, that's awesome. Just another reason why I should give Z shell a try.

In fact, I recently wrote a blog post about STDOUT and STDERR! I mention "2>&1":
http://tommystanton.com/entry/20120520-Standard-output-and-standard-error