[olug] Unix Tip: I SED BLANK

[Unix Guru Universe]

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			      UNIX GURU UNIVERSE 
			         UNIX HOT TIP

			Unix Tip 1875 - February 18, 2003

		    http://www.ugu.com/sui/ugu/show?tip.today

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I SED BLANK

Using sed, you can remove blank lines, and 
lines that contain only whitespace, from a 
file using the following:

sed -e '/^[     ]*$/d' InputFile >OutputFile

Within the single quotes ('), the forward 
slashes (/) delimit the regular expression 
that will be interpreted by sed.  The "d"
before the closing single quote, tells sed 
to delete any lines that match the regular 
expression.

Within the regular expression, the caret 
(^) matches the beginning of a line.  
The []* matches zero to many occurrences of 
the character list between the open bracket 
([) and the close bracket (]) (in the above 
regular expression, you must insert a space 
and a tab between the brackets).  The dollar 
sign ($) matches the end of a line.

These three constructs together match any 
blank line or any line that contains only 
spaces and tabs (in any combination).

Since the standard operation of sed is to 
echo lines to stdout, all lines except blank 
lines (or lines that only contain whitespace) 
will be sent to OutputFile.


This tip generously supported by: tim.couger at wcom.com



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