One Liners | Mohan Cheema's Online Diary

May 21, 2010
by Mohan Cheema
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Shell One Liners

Renaming file name.old to name.new – To test things first, insert ‘echo’ between ‘do mv’ (below).

$ for i in *.input; do mv $i ${i/name\.old/name\.new}; done

Running application in loops on many input files

$ for i in *.input; do ./application $i; done Read more...

May 21, 2010
by Mohan Cheema
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Simple AWK programs enclosed in single quotes can be typed and executed right at the Unix prompt. For example, the program

awk ‘BEGIN { FS = “:” } { print $1 | “sort” }’ /etc/passwd

This program prints a sorted list of the login names of all users. Read more...

April 28, 2010
by Mohan Cheema
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sed G

double space a file which already has blank lines in it. Output file should contain no more than one blank line between lines of text.

sed '/^$/d;G'

sed 'G;G'

sed 'n;d'

sed '/regex/{x;p;x;}'

sed '/regex/G'

sed '/regex/{x;p;x;G;}'

April 28, 2010
by Mohan Cheema
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List of one line perl programs to do many common command-line tasks. Read more...

perl my_file

perl -d -e 42

perl -w my_file

perl -d my_file