SED - basic text transformations on files or pipelines

sed is a stream editor for filtering and transforming text. A stream editor is used to perform basic text transformations on an input stream – a file or input from a pipeline. Sed works by executing commands, called sed scripts, on an input stream.

How to Use Sed

sed is invoked using the following syntax:

sed [options] 'command' inputfile

Where options is one or more sed options, command is a sed command, and inputfile is the name of the file to be processed by the sed command.

Sed Options

sed provides a number of options for controlling its behavior. Some of the more commonly used options are listed below.

Option	Description
`-n`	Suppress automatic printing of pattern space
`-e`	Execute the script provided as the next argument
`-f`	Execute the script provided in the file specified as the next argument

Sed Commands

sed provides a number of commands for performing text transformations. Some of the more commonly used commands are listed below.

Command	Description
`s/pattern/replacement/`	Replace the first occurrence of `pattern` with `replacement`
`s/pattern/replacement/g`	Replace all occurrences of `pattern` with `replacement`
`y/pattern/replacement/`	Transliterate the first occurrence of `pattern` with `replacement`
`y/pattern/replacement/g`	Transliterate all occurrences of `pattern` with `replacement`
`d`	Delete the pattern space and start next cycle

Sed Examples

The following examples demonstrate some of the ways in which sed can be used.

Example 1: Replace a String

In the following example, the sed command will replace the string oldstring with the string newstring.

sed 's/oldstring/newstring/' inputfile

Example 2: Replace a String (Global)

In the following example, the sed command will replace all occurrences of the string oldstring with the string newstring.

sed 's/oldstring/newstring/g' inputfile

Example 3: Transliterate a String

In the following example, the sed command will transliterate the string oldstring to the string newstring.

sed 'y/oldstring/newstring/' inputfile

Example 4: Transliterate a String (Global)

In the following example, the sed command will transliterate all occurrences of the string oldstring to the string newstring.

sed 'y/oldstring/newstring/g' inputfile

Example 5: Delete a Line

In the following example, the sed command will delete all lines that contain the string oldstring.

sed '/oldstring/d' inputfile

Example 6: Insert a Line

In the following example, the sed command will insert the string newstring on a new line after every line that contains the string oldstring.

sed '/oldstring/a\newstring' inputfile

Example 7: Insert a Line (Before)

In the following example, the sed command will insert the string newstring on a new line before every line that contains the string oldstring.

sed '/oldstring/i\newstring' inputfile

Example 8: Substitute on a Specific Line

In the following example, the sed command will replace the string oldstring with the string newstring on line 5 of the input file.

sed '5s/oldstring/newstring/' inputfile

Example 9: Substitute on a Range of Lines

In the following example, the sed command will replace the string oldstring with the string newstring on lines 5 through 10 of the input file.

sed '5,10s/oldstring/newstring/' inputfile

Example 10: Print Only Matching Lines

In the following example, the sed command will print only those lines that contain the string oldstring.

sed -n '/oldstring/p' inputfile

Example 11: Print Only Non-Matching Lines

In the following example, the sed command will print only those lines that do not contain the string oldstring.

sed -n '/oldstring/!p' inputfile

Example 12: Invert Matching Lines