Getting pipe return codes from SYSTEM command

I’m trying to find the return codes from bash for piped commands. i.e.

system(“ls”)

puts("#{$?.exitstatus}")

This returns the return code of ls

system(“ls | bzip2 -c > ./out.txt”)

how can I still get the return code of ls?

Thanks,

Russell.

On May 7, 2008, at 9:33 AM, Russell Quinn wrote:

how can I still get the return code of ls?

you cannot. this is a bash limitation.

if you need to do that use something like:

stdout = IO.popen(‘ls’){|pipe| pipe.read}

p $?.exitstatus

stdout = IO.popen(‘bzip2 -c’, ‘r+’){|pipe| pipe.write stdout;
pipe.close_write; pipe.read}

p $?.exitstatus

a @ http://codeforpeople.com/

Thanks for the reply. But there is a pipestatus array in bash isn’t
there?

ls | foo

echo ${PIPESTATUS[0]}

see:
http://aplawrence.com/Blog/B955.html

I just couldn’t get it to work from Ruby

system(“ls | bzip2 -c > ./out.txt”)

how can I still get the return code of ls?

If you’re using bash then it has an shell variable that records the exit
status of all commands in a pipeline (it’s an array). Do ‘man bash’.

Russell Quinn wrote:

ls | foo

echo ${PIPESTATUS[0]}

I just couldn’t get it to work from Ruby

try ‘ls | echo; exit ${PIPESTATUS[0]}’

On May 7, 2008, at 9:50 AM, Russell Quinn wrote:

I just couldn’t get it to work from Ruby

that’s because you’ve lost the bash process by the time bash exits.
use my session gem if you want a persistent bash session against which
to run commands:

require ‘session’

bash = Session::Bash.new

stdout, stderr = bash.execute ‘ls | grep something’
p bash.status

stdout, stderr = bash.execute ‘echo ${PIPESTATUS[0]}’
p bash.status

etc. session uses a single bash session for all it’s commands so
you can do this sort of thing. however i’m not sure what the point is
when pipelining from ruby, without shelling out, is so easy?

regards.

a @ http://codeforpeople.com/

try ‘ls | echo; exit ${PIPESTATUS[0]}’

Magical! thanks :slight_smile:

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