Re: pipefail with SIGPIPE/EPIPE

[Daniel Colascione]

On 02/15/2015 01:48 PM, Chet Ramey wrote:
> On 2/13/15 12:19 PM, Pádraig Brady wrote:
>> I was expecting bash to handle SIGPIPE specially here,
>> as in this context it's informational rather than an indication of error.
> 
> I don't agree.  It's a fatal signal whose default disposition is to
> terminate a process, which is exactly what happens in your example.

The purpose of pipefail is to make the shell indicate when something has
gone wrong anywhere in a pipeline. For most programs, SIGPIPE does not
indicate that something went wrong. Instead, SIGPIPE is expected
behavior. When pipefail spuriously reports expected behavior as an
error, Bash comes less useful.

> You might consider trapping or ignoring SIGPIPE in situations where it
> might be an issue.

If I were emperor of the world, I would make SIGPIPE's SIG_DFL action
terminate the process with exit status 0. But POSIX says we can't do
that. Even locally, I make my system do that without kernel surgery.
It's also not reasonable to modify every program that might be part of a
pipeline so that it exits successfully on EPIPE.

Making Bash treat SIGPIPE death as success is the next best option.

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