UNIX for Dummies Questions & Answers

I am using grep to find header info in a file and print it to another file. The header info only shows up on line 3 and 4 so i really don't need to search the remainder of the file. the grep -m option doesn't work with my version of UNIX. Also I'm new to UNIX so could you please explain what ever solution you may offer.

Code:

cat file1 | grep "header" | head -1

display the file
grep for a specific piece of text, here it is "header"
only display the first line of output

ALTERNATE

Code:

grep "header" <file1 | head -1

grep for specific text with input from file1
only display the first line of output

This ALTERNATE is more correct from a programming perspective, while the first is often easier for beginner programmers to understand.

Should this speed up the script runtime, by not searching deeper into the file? That is my end goal, and right now i can't tell if it is speeding up.
Thanks for your help thus far.

If you run interactivly, head will exit and break the pipe from the grep. On many unixes, that will cause it to stop immediatly. If you run without a TTY attached (perhaps from a scheduling tool like Control-M) , the behaviour can become rather unpredictable.

A sure-fire way to stop at the first instance is to script it yourself:

Code:

#!/usr/bin/perl
open(INFILE,"<file1") || die "Argh! $!";
while (<INFILE>) {
  if(/header/) { print $_ ; exit 0 }
}
exit 1

(Untested, but it should do the job)

Thanks everyone here is what i end up using:

head -5 $filename | grep "pattern"

this sped things up significantly