Invoking system(cmd) inside awk command

Shell Programming and Scripting
1

Hi,

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

2

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:

print cmd
system(cmd);
3

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?