sed

# remove third line
sed -i 3d <filename>
 
# insert line on beginning of a file
sed -i '1i MY_TEXT' <filename>
 
# String replace with sed
sed -i 's|STRING_FROM|STRING_TO|g' FILE
sed  -i 's|[#]*param=[yes|no]*|param=yes|g' FILE
 
# add line to a file
sed -i '13i\YOUR_TEXT' FILE
 
# add line before last line
sed -i '$i test_line' /path/to/file
 
# search block
sed -n '/FOO/,/BAR/p' /path/to/file
 
# remove digits
echo $FOO | sed 's/[^0-9]*//g' 
 
# remove blanks (trim)
cat FILE | sed 's/  */ /g'
# remove blanks and tabs
cat FILE | sed "s/[ \t][ ]*/ /g"
 
# write to file
sed 's/foot/bar/;w file'
 
# remove leading blank
sed "s/^[ ]*//"
 
# cat from to
sed -n '/^START/,/^END/p' /tmp/xx
 
# Uncomment all lines
sed -i 's/^/#/' /etc/locale.gen
 
# replace text recursively
find -type f -size -50k -exec sed -i 's|foo|bar|g' {} \;
 
# replace key = value
sed -i "s|^tag = .*|tag = ${NEW_VALUE}|g" /path/to/file
 
# remove string from string
echo "my foo bar" | sed -e s/foo//
 
# uncomment line
sed -i '/foo/s/^#//g' file
sed -i '/foo/, +1 s/^#//g' file
 
# comment in line
sed -i '/foo/s/^/#/g' file
sed -i '/foo/, +1 s/^/#/g' file