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Top Forums Shell Programming and Scripting test command looks strange... Post 302143720 by porter on Friday 2nd of November 2007 07:24:10 PM
Old 11-02-2007
Quote:
Originally Posted by jjinno
I just ran into this today, and don't know what to make of it...
Code:
if test x$SERVER = x
then
        echo $USAGE
        exit 1
fi

I know what everything in there does, except for the 'x' jazz...
It is effecitvely doing

Code:
if test "$SERVER" = ""
then
     ....

rather than using quotes, it prefixes an x to the string to ensure it's not an empty string argument. Where it falls down of course is if there is a space in $SERVER.
 

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EMPTY-PAGE(1)							 ExactImage Manual						     EMPTY-PAGE(1)

NAME
empty-page - empty page detector of the ExactImage toolkit SYNOPSIS
empty-page [option...] {-i | --input} input-file empty-page {-h | --help} DESCRIPTION
ExactImage is a fast C++ image processing library. Unlike many other library frameworks it allows operation in several color spaces and bit depths natively, resulting in low memory and computational requirements. empty-page counts dark pixels of a black and white image and decides with a threshold whether the page is most probably empty, and thus can be removed from the image processing stream. OPTIONS
-i file, --input file Read image from the specified file. -m n, --margin n Set width of border margin to skip. For speed reasons, the margin has to be a multiple of 8. The default is 16. -p x, --percentage x Set fraction of permissible dark pixels. The default is 0.05 (5%). -h, --help Display help text and exit. EXAMPLES
$ empty-page -i test.tif The image has 75461 dark pixels from a total of 1060992 (7.11231%). non-empty EXIT STATUS
The exit status is 0 if the image is mostly white, 1 otherwise. SEE ALSO
exactimage(7) AUTHORS
Jakub Wilk <jwilk@debian.org> Wrote this manual page for the Debian system. http://www.exactcode.de/site/open_source/exactimage/ This manual page incorporates texts found on the ExactImage homepage. COPYRIGHT
This manual page was written for the Debian system (and may be used by others). Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 or (at your option) any later version published by the Free Software Foundation. On Debian systems, the complete text of the GNU General Public License can be found in /usr/share/common-licenses/GPL-2. empty-page 09/09/2013 EMPTY-PAGE(1)
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