I have a lab question asking me to use grep with a regex pattern to match every word where the third letter from the beginning of the line is an "a" and save it with a redirect. How can I do that?

2 Answers 2


The solution proposed by @rahmu is simple if you look for low positions, but what if you look for the character number 25? Put in 25 dots?

In such a case the following solutions could be at hand. With grep

grep '^.\{24\}a' input >output

With awk

awk -F '' '$25 == "a"' input >output

This should answer your question:

grep -e "^..a" < input > savefile
  • Nice and simple solution. I don't think -e is even needed here - like grep ^..a < input > output should suffice.
    – user13742
    Commented Feb 20, 2012 at 16:34

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