I like to use these in combination with set -e and report the error that happened to whatever is capturing stdout for logging.
You can report the error code with $? at the start of your trap, IIRC.
“Exit traps” can make your Bash scripts more robust and reliable (2013)
21–30 of 159 posts
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#22I used an exit trap to kill an SSH agent that I am running, and I noticed that dash did not kill if the script was interrupted, but only if it ran to successful completion. I asked on the mailing list if this was expected behavior, and it turns out that POSIX only requires EXIT to run on a clean shutdown; to catch interruptions, add more signals. trap 'eval $(ssh-agent -k)' EXIT INT ABRT KILL TERM
You can't trap kill can you? doesn't that just go kill your process without any possibility of intervention or other actions? Also you probably want to handle HUP there too I would think (depending on what the script does)
That's what they put on the ticket, so that's what I'm using, but you're probably right.
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#23An annoying thing about bash is that EXIT will also run on SIGINT (^C), which most other shells won't (in my reading it's also not POSIX compliant, although the document is a bit vague). Some might argue this is a feature, but IMHO it's a bug – sometimes you really don't want cleanup to happen so people can inspect the contents of temporary files for debugging. Because trap doesn't pass the signal information to the…
> Because trap doesn't pass the signal information to the handler it's not hard not to do cleanup on SIGINT
Did you mean "it's hard" instead of "it's not hard"?
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#24I used an exit trap to kill an SSH agent that I am running, and I noticed that dash did not kill if the script was interrupted, but only if it ran to successful completion. I asked on the mailing list if this was expected behavior, and it turns out that POSIX only requires EXIT to run on a clean shutdown; to catch interruptions, add more signals. trap 'eval $(ssh-agent -k)' EXIT INT ABRT KILL TERM
You can't trap kill can you? doesn't that just go kill your process without any possibility of intervention or other actions? Also you probably want to handle HUP there too I would think (depending on what the script does)
SIGABRT is also not a normal termination signal. Seems out of place here.
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#25An annoying thing about bash is that EXIT will also run on SIGINT (^C), which most other shells won't (in my reading it's also not POSIX compliant, although the document is a bit vague). Some might argue this is a feature, but IMHO it's a bug – sometimes you really don't want cleanup to happen so people can inspect the contents of temporary files for debugging. Because trap doesn't pass the signal information to the…
Some temporary file remover. Lol indeed
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#26[deleted]
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#27An annoying thing about bash is that EXIT will also run on SIGINT (^C), which most other shells won't (in my reading it's also not POSIX compliant, although the document is a bit vague). Some might argue this is a feature, but IMHO it's a bug – sometimes you really don't want cleanup to happen so people can inspect the contents of temporary files for debugging. Because trap doesn't pass the signal information to the…
> Because trap doesn't pass the signal information to the handler it's not hard not to do cleanup on SIGINT Did you mean "it's hard" instead of "it's not hard"?
Oops, yes, thanks; seems a "not" got duplicated in editing – still within edit window.
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#28I wish there was a nicer shell scripting language that simply transpiled to Bash and would generate all this boilerplate code for me. There is https://batsh.org/ which has a nice syntax but it doesn't even support pipes or redirection, making it pretty worthless for shell scripting. I haven't found any other such scripting languages.
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#29An annoying thing about bash is that EXIT will also run on SIGINT (^C), which most other shells won't (in my reading it's also not POSIX compliant, although the document is a bit vague). Some might argue this is a feature, but IMHO it's a bug – sometimes you really don't want cleanup to happen so people can inspect the contents of temporary files for debugging. Because trap doesn't pass the signal information to the…
Some temporary file remover. Lol indeed
"Keep non-temporary files intact" was not part of the design document.
Re: “Exit traps” can make your Bash scripts more robust and reliable (2013)
#30I used an exit trap to kill an SSH agent that I am running, and I noticed that dash did not kill if the script was interrupted, but only if it ran to successful completion. I asked on the mailing list if this was expected behavior, and it turns out that POSIX only requires EXIT to run on a clean shutdown; to catch interruptions, add more signals. trap 'eval $(ssh-agent -k)' EXIT INT ABRT KILL TERM
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