Invoking system(cmd) inside awk command


 
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# 1  
Old 12-30-2013
Invoking system(cmd) inside awk command

Hi,

I was searching for a way to grep 2 lines before and after a certain keyword, and I came across the following code..

Code:
awk "\$0 ~ /ORA-/ { 
cmd=\"awk 'NR>=\" NR-2 \" && NR<=\" NR+2 \"' init.ora\"
system(cmd)
}" input_file

I could not understand how this works. What is system() ? what does that do? Can someone please help me understand what the above command does? Curious to know.

Thanks.

Last edited by Kulasekar; 12-30-2013 at 07:14 PM.. Reason: awk, context grep, system, invoking functions in awk
# 2  
Old 12-30-2013
system(expression) executes the command given by expression and return the exit status of the command.

The awk program that you posted is looking for a pattern ORA- in the file: input_file

Once found, it is prints records between NR-2 && NR+2 from file: init.ora

NR is current input record # with pattern ORA- in the file: input_file

You can put a print statement to understand what is going on:
Code:
print cmd
system(cmd);

# 3  
Old 12-31-2013
What would be the input file? To me, that script made sense only if input_file actually is init.ora.
Did you consider grep's -A and -B options?
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