Return value of piped command?

Shell Programming and Scripting
1 
grep $SEARCH_STRING /etc/passwd | cut -d":" -f 1,5

I need to check the $? value of grep in the above. If I place a test for $? after the above piped command, it returns success status of grep piped to cut.

How can I get the success status of grep alone?

2

Different shells have different mechanisms for dealing with this situation.

Bash 3.0+ and ksh93 have the pipefail option (set -o pipefail) which changes the exit code behavior of pipelines and reports the exit code of the pipeline as the exit code of the last program to return a non-zero exit code.

Bash has the PIPESTATUS array variable which contains a list of exit status values from the processes in the most-recently-executed foreground pipeline

zsh has pipestatus.

Another way is to use coprocesses.

3

I'm using ksh and the command set -o pipefail fails with the message

ksh: pipefail: bad option(s)

Can you please throw more light on coprocesses and the usage?

4

Then you are apparantly using either ksh88 or pdksh.

5

You to combine exit statuses logically, so that you can test more than one thing at a time.

statement1 && statement2

means execute statement1 and if its exit status is 0 (sucessful) then execute statement2

statement1 || statement2

means execute statement1 and if its exit status is not 0 then execute statement2

Regards

6

But you can't do that in a pipeline.

Another makeshift solution would be to invoke a subshell and have it somehow smuggle out the exit status to a dedicated file descriptor. I don't think we want to go there, though.