Programming

I need to run an interactive program in the background so I can grep it for specific data to use for some logic in a script.

There is no quiet or background mode on the program so I plan to redirect a document with commands in it and then to grep the output.

This is almost working, except that then some lines I haven't grepped for are also appearing - this I don't understand - I thought grep would work on all output to STDOUT (I've tried redirecting STDERR too but that doesn't seem to help).

See example:

Code:

/usr/sap/XXX/SYS/exe/run/jcmon pf=/sapmnt/XXX/profile/START_JC10_bdhp4530 < txtj | egrep 'dispatcher|server|SDM'
 
[Thr 01] Wed Jun 20 06:54:01 2012
[Thr 01] MtxInit: -2 0 0
|  0|dispatcher          |   27390|Running             |    0|yes    |
|  1|server0             |   27391|Running             |    0|yes    |
|  2|SDM                 |   27392|Running             |    0|yes    |

Notice two lines which strangely get written to the output
[Thr 01] Wed Jun 20 06:54:01 2012
[Thr 01] MtxInit: -2 0 0

How are these getting there?
I thought there were only two channels for output to screen in UNIX
STDOUT
and
STDERR

However if I running the main command (without the egrep) and redirect either STDOUT (1>) or STDERR (2>) to /dev/null - then the ONLY lines that show up are those two lines - this works identically no matter which output of those two I redirect....
[Thr 01] Wed Jun 20 06:54:01 2012
[Thr 01] MtxInit: -2 0 0

Weird - any thoughts?

---------- Post updated at 12:38 ---------- Previous update was at 12:00 ----------

NB An alternate fix for my issue would be to be able to call a command but with a time limit -- i.e. if this command returns no output within 5 seconds then kill it.... any ideas on this alt? If I can find a thread on that alternative I'll link it in here.

You want to redirect stderr to stdout, not /dev/null, i.e. 2>&1