sed

sed stands for stream editor. The operations do not modify the original file, they just printed as stdout.

Option	Description
s	substitution (replace)
g	global (across the whole file)
d	delete line
p	print line
-i	inplace changes

Deletion

# delete the first line
sed '1d' <file>

# delete the last line
sed '$d' <file>

# delete multiple lines
sed '1,7d' <file>

# delete every word that starts with '1' inplace
sed -i '/^1/d' <file>

Substitution

# substitution
sed 's/<to-be-replaced>/<to-replace-with>/g' <file>
 
# remove white space with substitution
sed 's/ //g' <file>

# remove everything after
sed 's/<pattern>.*//g'

Filtering

# print specific line ranges
sed -n '1,3p' <file>