On 2/18/22 00:27, Ulrich Eckhardt wrote:
- Shell scripting uses nonzero exit codes to signal errors by default.
grep is an exception here (as are cmp, diff and sort as I understand
you),
I'm sure there are other exceptions. And there's a long tradition for
these exceptions. It doesn't sound realistic to upend this longstanding
practice, or to add options to every such program.
- Also, just arguing in the context of grep, there is an option to
"just tell me if there was a match, don't give me the results"
That's for efficiency; grep can be waaay faster with -q. There is no
efficiency argument for the changes you're proposing.
The following
causes Bash to exit on GNU/Linux:
set -eo pipefail
cat /usr/share/dict/american-english | grep -l '^'
This is not because of anything 'grep' does, as 'grep' exits with
status zero. It's because 'cat' exits with nonzero status. Surely we
shouldn't add a --pipe option to 'cat' too.
It doesn't do that here, I wonder why you are seeing an error there?
Possibly you're using a GNU/Linux variant where the dictionary is
located elsewhere? Or you have something in your .profile? I'm running
Ubuntu 21.10 x86-64, and if I run this shell command:
bash --norc --noprofile -c 'set -eo pipefail; cat
/usr/share/dict/american-english | grep -l "^"; echo done'
the output is:
(standard input)
which means that Bash exited without doing the 'echo done'.
Also, if it did, that would signal an actual error, which is behaviour
I'm completely fine with.
There is no actual error, in that the "cat ... | grep ..." command does
just what I wanted it to: grep reported that standard input contained a
match (which it did). This may help to explain my previous remark that
scripts that use "set -eo pipefail" need to be verrrry careful.
