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Sed

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Short for "Streamline Editor", sed allows you to run a file through it and either match or change data without actually editing the file itself.
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Short for "Streamline Editor", sed allows you to run a file through it and either match or change data without actually editing the file itself. This can be particularly handy if you need to make a lot of similar changes to a file -- e.g., you find out you consistently put in a wrong hostname in a configuration file, and you need to change your conf file to point to the right server....except the same change needs to be made 100 times. [[sed]] to the rescue.
  
 
The most common usage is to change all instances of a phrase to another; to wit:
 
The most common usage is to change all instances of a phrase to another; to wit:

Revision as of 16:45, 29 September 2004

Short for "Streamline Editor", sed allows you to run a file through it and either match or change data without actually editing the file itself. This can be particularly handy if you need to make a lot of similar changes to a file -- e.g., you find out you consistently put in a wrong hostname in a configuration file, and you need to change your conf file to point to the right server....except the same change needs to be made 100 times. sed to the rescue.

The most common usage is to change all instances of a phrase to another; to wit:

dave@samizdata:~% cat sed_testfile
 dave
 dave
 davedave
 jimbo
 dave
 freebsd
dave@samizdata:~% sed s/dave/david/ sed_testfile
 david
 david
 daviddave
 jimbo
 david
 freebsd
dave@samizdata:~% more sed_testfile
 dave
 dave
 davedave
 jimbo
 dave
 freebsd
dave@samizdata:~%

As you can see, the changes were not actually made to the file. I didn't tell it to put the changes anywhere! Easily fixed with the help of redirection:

dave@samizdata:~% sed s/dave/david/ sed_testfile > sed_testfile_new
dave@samizdata:~% more sed_testfile_new
 david
 david
 daviddave
 jimbo
 david
 freebsd
dave@samizdata:~%
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