Recipe : Basic sed primer

Substitution(Replacement) with sed
==================================
$ sed 's/pattern/replace_string/' file

$ cat file | sed 's/pattern/replace_string/' file

Saving changes in file
======================
$ sed 's/text/replace/' file > newfile
$ mv newfile file

$ sed -i 's/text/replace/' file


Global substitution
===================
$ sed 's/pattern/replace_string/g' file

$ echo this this this this | sed 's/this/THIS/2g' 
this THIS THIS THIS 

$ echo this this this this | sed 's/this/THIS/3g' 
this this THIS THIS 

$ echo this this this this | sed 's/this/THIS/4g' 
this this this THIS 

sed delimiters
==============
$ sed 's:text:replace:g'
$ sed 's|text|replace|g'

delimiter in pattern
====================
sed 's|te\|xt|replace|g' 


Removing blank lines
====================
$ sed '/^$/d' file 


Matched string notation
=======================
$ echo this is an example | sed 's/\w\+/[&]/g' 
[this] [is] [an] [example]


Substring match notation (\1)
=============================
$ echo this is digit 7 in a number | sed 's/digit \([0-9]\)/\1/' 
this is 7 in a number

$ echo seven EIGHT | sed 's/\([a-z]\+\) \([A-Z]\+\)/\2 \1/' 
EIGHT seven 


Double quotes in sed
====================
$ text=hello
$ echo hello world | sed "s/$text/HELLO/" 
HELLO world