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Quick Question on sed command in shell script

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# 1  
Old 09-10-2008
Quick Question on sed command in shell script
Hello,
I have the following line in one of my shell scripts. It works fine when the search string($SERACH_STR) exists in the logfile($ALERTLOG) but if the search string does not exist this line errors out at run time. Is there a way to make this line return 0 if it is not able to find the search string in the log file?

START_LINE=`grep -n "$SEARCH_STR" $ALERTLOG | head -1 | sed 's/:/ /' | awk '{print $1}'`


Thanks.
# 2  
Old 09-10-2008
Or is there a way to trap the error generated by this command when it fails to find the search string?

Thanks
# 3  
Old 09-10-2008
Near as I can tell, awk does support if/else, although I must confess to not having tried this before... I'll look into it and see what I can see...

- Avron
# 4  
Old 09-10-2008
Something like:
Code:
awk -v s=$SEARCH_STR '$0~s{exit(1)}END{exit}' $ALERTLOG
START_LINE=$?

Regards
Last edited by Franklin52; 09-10-2008 at 06:02 PM.. Reason: correcting code
# 5  
Old 09-10-2008
Best that I could come up with is to assign `grep -n "$SEARCH_STR" $ALERTLOG | head -1` to a variable. If $variable, then proceed to the sed.

Since my arrival here at unix.com, I've constantly been amazed by the knowledge of people like Franklin52, era, jim mcnamara, et al.
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