Bash piped commands and its returns

Question

Is there any way to a piped commands to replicate its previous command exit status?

For example:

#/bin/bash
(...)
function customizedLog() {
   # do something with the piped command output
   exit <returned value from the last piped comand/script (script.sh)>
}

script.sh | customizedLog
echo ${?} # here I wanna show the script exit value
(...)

I know I could simply check the return using ${PIPESTATUS[0]}, but I really want to do this like the customizedLog function wasn't there.

Any thoughts?

Jonathan Leffler · Accepted Answer · 2015-04-24 15:34:21Z

4

In bash:

set -o pipefail

This will return the last non-zero exit status in a pipeline, or zero if all commands in the pipeline succeed.

set -o pipefail
script.sh | customizedLog
echo ${?}

Just make sure customizedLog succeeds (return 0), and you should pick up the exit status of script.sh. Test with false | customizedLog and true | customizedLog.

answered Apr 24, 2015 at 15:34

Jonathan Leffler

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2 Comments

VeryNiceArgumentException Over a year ago

It's not exactely what I was imagining but tottaly solved my issue! Thanks Jonathan

mklement0 Over a year ago

This is especially handy if multiple pipelines must be handled this way; as an ad-hoc solution the OP's own approach - even though he dismissed it - is worth reiterating: echo ${PIPESTATUS[0]} provides the same result without the need to change a global shell option (or, more simply, given that the first array element is being accessed, echo $PIPESTATUS.

Petr Skocik · Accepted Answer · 2015-04-24 15:59:54Z

2

script.sh | customizedLog

The above will run in two separate processes (or 3, actually -- customizedLog will run in a bash fork as you can verify with something like ps -T --forest). As far as I know, with the UNIX process model, the only process that has access to a process's return information is its parent so there's no way customized log will be able to retrieve it.

So no, unless the previous command is run from a wrapper command that passes the exit status through the pipe (e.g., as the last line):

( command ; echo $? ) | piped_command_that_is_aware_of_such_an_arrangement

answered Apr 24, 2015 at 15:59

Petr Skocik

60.6k7 gold badges106 silver badges165 bronze badges

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