On 04/08/2010 06:49 AM, Bob Proulx wrote:
Vadym Chepkov wrote:
I found out a very unusual feature of bash which makes it to act
really unexpected. I understand that pipelines are executed in a
separate subshell, but I really think 'exit' command should be
absolute. Consider a trivial code:
Note that dash also behaves this way too.
#!/bin/bash
echo Start
ps -ef | while read proc
do
echo $proc
exit 1
done
echo Continue
I would expect never see "Continue" printed, I didn't put any
conditional checks to simplify the example, but I really expect the
script to be completely aborted when it gets to 'exit', not having
to add additional checks or replace pipeline with temporary files
This is a variation on Bash FAQ E4. Pipes create subshells.
You can avoid this by avoiding piping to the while loop. Instead use
a redirection and no subshell will be created.
#!/bin/bash
echo Start
while read proc
do
echo $proc
exit 1
done< <(ps -ef)
echo Continue
The "<(command)" syntax is documented in the Process Substitution
section of the manual.
Bob
ksh works a bit differently. It also creates subshells, except possibly
the last command. Therefor in this case while loop is not subshell and
exit exits the whole script.
RR
