Exit bash script on error in loop

[Johnny Rosenberg]

2013/9/12 Paul Smith <paul at mad-scientist.net>

> On Thu, 2013-09-12 at 23:16 +0200, Johnny Rosenberg wrote:
> > I did some more experiments and I found that it's my pipe to a yad
> > progress bar that cause the problem. Unfortunately I didn't include it
> > in my example, but here's another example,
>
> Err... yes, that makes ALL the difference.
>
> The way the shell works with pipelines is that each section of the
> pipeline is really run in a different process [*].  It pretty much HAS
> to work that way since you want all the different parts of the pipeline
> working at the same time, reading from and writing to pipes, and shells
> are not multithreaded.  Hence, different processes.
>
> So, the exit command in the first part of the pipeline exits from that
> process (shell) but doesn't exit from the parent process (main script).
> There's pretty much nothing you can do about that.
>
> Depending on exactly what you want to accomplish there may be tricks you
> can play.  Instead of exit, you can use kill to kill the shell script.
>

Sounds a bit brutal, or even overkill… :P


> You can use a named pipe instead of a regular pipe, and have each
> section write/read from the pipe in the background as appropriate
> without using a pipeline.
>

I'm not sure what a named pipe is, but I will do some searching.


>
> Or you can switch to a more sophisticated scripting language such as
> Perl or Python, that can handle this with ease.
>

Well, I actually started to learn Python, but then I suddenly woke up and
remembered that I have a life… :P
But I am sure I will try it again some time.


>
>
> [*] ksh has a special feature where the last element in the pipeline is
> run in the current shell, which is slightly more efficient and is very
> handy in some situations.  But, it's not required by POSIX and not
> portable, and bash doesn't implement it.
>

Well, I don't care much about portability. The worst thing that could
happen with a script that I write would probably be that someone succeeds
running it in Windows… ha ha ha… I would really hate that! Maybe I could
create some kind of license or something, prohibiting people from doing
that…


Johnny Rosenberg


>
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