Re: if source command.sh & set -e issue

[Greg Wooledge]

On Wed, Jul 24, 2024 at 20:53:33 +0300, Mor Shalev via Bug reports for the GNU 
Bourne Again SHell wrote:
> *if source command.sh ; then  echo passfi*
> Or, similarly:
> 
> *source command.sh && echo pass*

Remember how -e is defined:

              -e      Exit  immediately  if a pipeline (which may consist of a
                      single simple command), a list, or  a  compound  command
                      (see SHELL GRAMMAR above), exits with a non-zero status.
                      The shell does not exit if the  command  that  fails  is
                      part  of  the command list immediately following a while
                      or until keyword, part of the test following the  if  or
                      elif  reserved  words, part of any command executed in a
                      && or || list except the command following the final  &&
                      or ||, any command in a pipeline but the last, or if the
                      command's return value is being inverted with !.


With that in mind, let's re-establisg our setup, with two variants for
the initial script:


hobbit:~$ cat script1.sh
#!/bin/bash
echo script.sh begin
source command.sh && echo pass
echo script.sh end
hobbit:~$ cat script2.sh
#!/bin/bash
echo script.sh begin
source command.sh
test $? = 0 && echo pass
echo script.sh end
hobbit:~$ cat command.sh
set -e
echo command.sh start
false
echo command.sh end


Now compare:


hobbit:~$ bash-5.2 script1.sh
script.sh begin
command.sh start
command.sh end
pass
script.sh end
hobbit:~$ bash-5.2 script2.sh
script.sh begin
command.sh start


So, we can see what happened here.  In script1.sh, command.sh is sourced
by a command which is "part of any command executed in a && or || list
except the command following the final && or ||".  And therefore, set -e
does not trigger.

In script2.sh, the source command is NOT part of the command list
following while/until, nor part of the test following if/elif, nor any
part of a &&/|| list.  And set -e triggers.

So this would appear to be part of an intended change, to make the
behavior of -e satisfy the documented requirements.

Please remember, -e is *not* intended to be useful, nor is it intended
to be intuitive.  It's intended to be *bug compatible* with whatever
interpretation the POSIX committee has agreed upon this year.  This
interpretation changes over time, so the behavior of -e also changes.