Handy awk commands

 

Using UNIX tools such as sed (string editor) and awk (named after Aho, Weinberg and Kernigan) are indispensible skills for the Oracle professional on UNIX and Linux.

In addition, Oracle shell scripting is required for effective file manipulation as described in the book "Oracle Shell Scripting" by Oracle guru Jon Emmons.

This great web page shows awk in-action, dozens of handy awk commands for easy file manipulation in UNIX and Linux.  Here are my favorites:

Substitute (find and replace) "foo" with "bar" on each line.

awk '{ sub(/foo/,"bar"); print }'

(Note:  You can also do this change all in vi with sed (invoked with "s"), like this:

<exc>:.,$s/foo/bar/g

Change "scarlet" or "ruby" or "puce" to "red".

awk '{ gsub(/scarlet|ruby|puce/, "red"); print}'

Remove duplicate, consecutive lines (emulate "uniq")

awk 'a !~ $0; { a = $0 }'

Convert Windows/DOS newlines (CRLF) to Unix newlines (LF) from Unix.

awk '{ sub(/\r$/,""); print }'

Convert Unix newlines (LF) to Windows/DOS newlines (CRLF) from Unix.

awk '{ sub(/$/,"\r"); print }'

Delete leading whitespace (spaces and tabs) from the beginning of each line (ltrim).

awk '{ sub(/^[ \t]+/, ""); print }'

Delete trailing whitespace (spaces and tabs) from the end of each line (rtrim).

awk '{ sub(/[ \t]+$/, ""); print }'

Delete both leading and trailing whitespaces from each line (trim).

awk '{ gsub(/^[ \t]+|[ \t]+$/, ""); print }'

Insert 5 blank spaces at beginning of each line.

awk '{ sub(/^/, "     "); print }'

 

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