Thursday, November 15, 2012

How to filter files using the sed command in Unix

If you need to filter a file and keep only those line thta contain specific chracter/string you can use grep command
http://milospjanic.blogspot.com/2012/11/how-to-use-grep-to-select-specific.html

but also you can use sed

sed -n 's/yes/&/p' file.txt>file2.txt

sed -n will output nothing unless the printing command is found (p). In this case sed will find those lines that contain "yes" and substitute them with the same string (&), i.e. there will be no substitute but it will print this line that is found in the output (p).

Output will be saved in file2.txt.

Nice tutorial on sed command:
http://www.grymoire.com/Unix/Sed.html#uh-3

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