Special Commands
The shell includes several powerful text-processing commands. The three most common are sed, awk, and grep, and they are often used together with sort.
grep - search text
grep finds lines matching a pattern:
echo "apple banana" | grep banana
Output:
apple banana
sed - stream editor
sed transforms text. Replacing every apple with orange:
echo "apple pie" | sed 's/apple/orange/'
Output:
orange pie
awk - text processing
awk splits lines into fields and prints selected columns:
echo "apple banana cherry" | awk '{print $2}'
Output:
banana
sort - sort lines
sorted lines can be reordered alphabetically:
printf "cherry\napple\nbanana\n" | sort
Output:
apple
banana
cherry
These commands are the building blocks of almost every shell pipeline.
Exercise
Complete the pipeline below so that it prints the third field ($3) of the line apple banana cherry, which is cherry.
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