Re: "exit" doesn't work from inside of PIPED read block

[Bob Proulx]

Blaine Simpson wrote:
> Bob Proulx wrote:
> > Please keep the mailing list in the CC so that others may participate
> > in the discussion and enable it to be available in the archives.

Grr...  This means please do a list reply in your mailer or if list
reply is not available then use the followup to all or reply to all
action.

> >> #!/bin/bash -p
> >
> > Why are you using the -p option?
> >   
> To prevent possible side effects from inheriting shell functions from
> current environment, SHELLOPTS, any settings in $ENV, etc.  Why would I
> want to have all that crap in my environment if my goal is to test
> exactly what I have coded in my script?

If you have crap in your environment then you should fix that problem
first.  It led me to believe that you were trying to run a setuid
script or something.

> > In another terminal look at the processes running.  I used 'ps -efH'.
> > Look for pid 8924.
> >
> >   rwp       8924  8923  0 10:10 pts/36   00:00:00     bash
> >   rwp       1016  8924  0 10:13 pts/36   00:00:00       sleep 123
>
> VERY interesting.  Thanks very much.

Glad to help.

Bob


Blaine Simpson wrote:
> Bob Proulx wrote:
> > Please keep the mailing list in the CC so that others may participate
> > in the discussion and enable it to be available in the archives.
> >
> >   
> >> #!/bin/bash -p
> >>     
> >
> > Why are you using the -p option?
> >   
> To prevent possible side effects from inheriting shell functions from
> current environment, SHELLOPTS, any settings in $ENV, etc.  Why would I
> want to have all that crap in my environment if my goal is to test
> exactly what I have coded in my script?
> >> echo $$
> >> cat /tmp/atf | while read; do echo $$; exit 3; done
> >>     
> >
> > In both cases the $$ is expanded by the shell before invoking the
> > command.  So they get the same pid value, the pid of the parent.
> >
> > I don't know how to output the pid of the subshell.  Perhaps someone
> > on the mailing list will have an answer.
> >
> > You can verify that there is a subshell however.
> >
> >   echo $$ ; echo foo | sleep 123
> >   8924
> >   ...sleep 123 now running...
> >
> > In another terminal look at the processes running.  I used 'ps -efH'.
> > Look for pid 8924.
> >
> >   rwp       8924  8923  0 10:10 pts/36   00:00:00     bash
> >   rwp       1016  8924  0 10:13 pts/36   00:00:00       sleep 123
> >
> > Bob
> >   
> VERY interesting.  Thanks very much.
> > Blaine Simpson wrote:
> >   
> >> Thanks for taking the time to answer (both), Bob.  Inline reply below.
> >>
> >> Bob Proulx wrote:
> >>     
> >>> Blaine Simpson wrote:
> >>>   
> >>>       
> >>>>  "exit" doesn't exit the current shell when inside of PIPED read blocks,
> >>>>     yet everything works find if the input comes from "redirection".
> >>>>     
> >>>>         
> >>> This is because pipes operate in subshells and the exit applies to the
> >>> subshell.  Please see the bash FAQ question E4 for more information.
> >>>
> >>>   ftp://ftp.cwru.edu/pub/bash/FAQ
> >>>
> >>>   
> >>>       
> >>>>     cat /tmp/atf | while read; do exit 3; done  # for any text file 
> >>>> /tmp/atf
> >>>>     Yet the following works
> >>>>     cat /tmp/atf | while read; do exit 3; done
> >>>>     
> >>>>         
> >>> Those two are the same.  You probably meant to say:
> >>>
> >>>   while read; do exit 3; done < /tmp/atf
> >>>   
> >>>       
> >> Exactly.  Copy and paste error from the file where my notes are.
> >>     
> >>> No pipeline there and so that is done in the current shell.
> >>>   
> >>>       
> >> I thought I had eliminated shelling as the cause because I echo'd $$ in
> >> the body (where "exit 3" is above), and it is the same exact pid as the
> >> root shell.
> >>
> >> I'm attaching the test script.
> >>     
> >>> Bob
> >>>   
> >>>       
> >
> >   
> >> #!/bin/bash -p
> >>
> >> echo $$
> >> cat /tmp/atf | while read; do echo $$; exit 3; done
> >>
> >> # WORKS:
> >> #while read; do exit 3; done < /tmp/atf
> >>
> >> echo "Post in $$"
> >>     
>