Riccardo Riva

The following is a simple memo on how to use the three powerful tools above.
It will not be a complete guide, and you should find only a small part of the possible use, but this would be a review only for the most common use (for me) and would not go a deep dive.

Grep

grep : print lines matching a pattern (equals “grep -G” which is the default)
egrep : equals grep -E (interpret extended regexp)

grep -n : line numbered
grep -i : ignore case
grep -c : count matches
grep -v : print non-matching lines
grep -r : recursivity, read all files under each directory

grep pattern file.txt

Will display the lines containing the pattern

grep -c pattern file.txt

Will display how many lines contain the pattern

grep -i pattern file.txt

Will display the lines containing the pattern regardless of the case

grep -A 1 -B 1 pattern output.txt

Will print the one line before (-B) and one line after (-A) the matching pattern

Awk

awk '{ print $0 }' file

Output the content of the file

awk '{ print $2 }' file

Output the second field of data of the file, space is the default separator

awk -F ':' '{ print $2 }' file

Same but separator is “:”

Sed

cat file | sed -e 's/old_pattern/new_pattern/g'

sed would replace old_pattern by new_pattern in the output

cat file | sed -e '4,10s/old_pattern/new_pattern/g'

sed would replace old_pattern by new_pattern in the output between line 4 and 10

cat file | sed '/pattern/d'

Delete a pattern

cat file | sed '/pattern/!d'

Delete everything but the pattern (this equals grep “string_to_remove”)

Hope this help

Bye
Riccardo

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