5.2.4. Find and replace with sed
In the example file, we will now search and replace the errors instead of only (de)selecting the lines containing the search string.
sandy ~> sed 's/erors/errors/' example
This is the first line of an example text.
It is a text with errors.
Lots of errors.
So much errors, all these erors are making me sick.
This is a line not containing any errors.
This is the last line.
sandy ~>
As you can see, this is not exactly the desired effect: in line 4, only the first occurrence of the search string has been replaced, and there is still an 'eror' left. Use the g command to indicate to sed that it should examine the entire line instead of stopping at the first occurrence of your string:
sandy ~> sed 's/erors/errors/g' example
This is the first line of an example text.
It is a text with errors.
Lots of errors.
So much errors, all these errors are making me sick.
This is a line not containing any errors.
This is the last line.
sandy ~>
To insert a string at the beginning of each line of a file, for instance for quoting:
sandy ~> sed 's/^/> /' example
> This is the first line of an example text.
> It is a text with erors.
> Lots of erors.
> So much erors, all these erors are making me sick.
> This is a line not containing any errors.
> This is the last line.
sandy ~>
Insert some string at the end of each line:
sandy ~> sed 's/$/EOL/' example
This is the first line of an example text.EOL
It is a text with erors.EOL
Lots of erors.EOL
So much erors, all these erors are making me sick.EOL
This is a line not containing any errors.EOL
This is the last line.EOL
sandy ~>
Multiple find and replace commands are separated with individual -e options:
sandy ~> sed -e 's/erors/errors/g' -e 's/last/final/g' example
This is the first line of an example text.
It is a text with errors.
Lots of errors.
So much errors, all these errors are making me sick.
This is a line not containing any errors.
This is the final line.
sandy ~>
Keep in mind that by default sed prints its results to the standard output, most likely your terminal window. If you want to save the output to a file, redirect it:
sed option 'some/expression' file_to_process > sed_output_in_a_file
More examples
Plenty of sed examples can be found in the startup scripts for your machine, which are usually in /etc/init.d or /etc/rc.d/init.d . Change into the directory containing the initscripts on your system and issue the following command:
grep sed *
Prev
Home
Next
Introduction
Up
Non-interactive editing
* License
