Redirecting stdout on background task

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# 1  
Old 07-25-2011
Redirecting stdout on background task


I have a script ( which invokes the GStreamer command-line tool gst-launch with all the correct command line parameters. When I invoke this program, I add the '&' character at the end to make it a background task, so that my script can complete and exit, i.e.

gst-launch .... &

When I look at the process list, gst-launch appears correctly.

 1211 ttyS2    00:00:01 gst-launch-0.10
 1227 ttyS2    00:00:00 ps

However, when invoked, the gst-launch program spits out some information on stdout which I need to capture in my script before exiting. I thought I could just redirect the output to a file (actually, i'm using a named-pipe), like this...

gst-launch .... >gstpipe &

Unfortuantely, whilst the stdout information does indeed appear in the gstpipe file, the process list doesn't show gst-launch anymore, but the original script instead. I.e.

 1414 ttyS2    00:00:00
 1438 ttyS2    00:00:00 ps

This appears in the process list, even after my script has exited, indicating that when invoking gst-launch, the shell is creating a new process, but with the wrong name.

What am I doing wrong here??

Thanks for any help,

Last edited by radoulov; 07-25-2011 at 09:45 AM.. Reason: Code tags.
# 2  
Old 07-25-2011
you cannot see process list because of `...>pipe` command cause this process to wait.Therefore you can see only and not gst-launch.
gst-launch .... >gstpipe &

if you try to read from the pipe with another process then you can see gst-launch process.
# tail -f mypipe & ps -ef|grep gst

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