Deleting all lines that contain specific data

Q: On the UNIX systems, how do I delete every line in a file that has the word "outdated" in it?

A: The two easiest ways are using the grep -v command at the UNIX prompt or the ex/vi g and d commands.

Using grep -v

grep -v outdated myfile > myfile.new

This example looks for the text "outdated" in the file named "myfile". But since you included the "-v" option, it displays the lines that do not have "outdated" in them. Using UNIX's redirection symbol and another file name tells the system to put the lines in that file.

To summarize: this command searches the file "myfile" for the text "outdated", and puts all lines that do not have "outdated" in them into the file "myfile.new".

grep -iv outdated myfile > myfile.new

By adding the "-i" option, you tell grep to ignore the case of the text "outdated".

This command searches the file "myfile" for the text "outdated"--no matter whether upper-case or lower-case letters have been used--and puts all lines that do not have "outdated" in them into the file "myfile.new".

grep -iv "out dated" myfile.new > myfile.newer

In this example, we tell grep to look for "out dated"--with the space in the middle.

This command searches the file "myfile.new" for the text "out dated"--no matter whether upper-case or lower-case letters have been used--and puts all lines that do not have "out dated" in them into the file "myfile.newer".

Using vi global commands

:set ic
(set ignorecase)

:g/outdated/d

This command tells vi to do a global search for "outdated" and to delete any line containing that text.

:g/out dated/d

This command tells vi to do a global search for "out dated" and to delete any line containing that text--including the space.