grep

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grep

grep

grep searches input for lines matching a pattern and prints the matching lines. Common flags include -i (case-insensitive), -v (invert match), -n (show line numbers), and -r (recursive over a directory). It's one of the most frequently used text-processing tools in shell scripting.

Note: grep -v pattern prints every line that does *not* match — useful for filtering out noise.

Example: grep

bash

#!/bin/bash
printf "apple\nbanana\ncherry\navocado\n" > fruits.txt

echo "Lines containing 'a':"
grep "a" fruits.txt

echo "Lines starting with 'a':"
grep "^a" fruits.txt

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Running Commands in the Background (&) and $!
grep
The wait Command
Process IDs and the ps Command
cut
Signals and trap
sort
Subshells vs the Current Shell ( ( ) vs { } )
uniq
Command Substitution vs Process Substitution
wc
Killing Processes

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grep

grep

Chapter Quiz — Complete all 12 topics to unlock

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