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Full Discussion: IF statement with square brackets
Top Forums Shell Programming and Scripting IF statement with square brackets Post 302983624 by Don Cragun on Friday 14th of October 2016 03:21:22 AM
Old 10-14-2016
The real question is not what the region is when the code works or fails, but to what do the expansions of the three shell variables: com_dir, dup_file_name_chk, and save_dir expand when the code works and to what do they expand when it fails. One might guess that it is failing when one of those variables contain one or more whitespace characters. One might also guess that the following would also work:
Code:
if [ -f "$com_dir/$dup_file_name_chk" ] || 
[ -f "$save_dir/$dup_file_name_chk" ]
then
.
.
.
fi

You haven't told us what shell you're using, but if [[ expression ]] is working and you're running on AIX, I'll assume you are using ksh or bash. The command:
Code:
[ -f $com_dir/$dup_file_name_chk ]

is a shell built-in utility that performs the same parameter expansion and field splitting that happens whenever the shell evaluates a command line. Without the double quotes surrounding the parameter expansions, if there are whitespace characters in the expansions of those variables, field splitting will cause one or both of those tests to fail. It will also fail if $dup_file_name_chk expands to an empty string. but in that case the double bracket test would also fail.

The command:
Code:
[[ -f $com_dir/$dup_file_name_chk ]]

is part of the syntax of the shell; not a utility. Parameter expansion still occurs in this case, but field splitting does not occur.
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LEARN ABOUT DEBIAN

gchem3d

GCHEM3D(1)						       gnome-chemistry-utils							GCHEM3D(1)

NAME

       gchem3d - a small chemical viewer application

SYNOPSIS

       gchem3d [OPTION(S)...] [FILE...]

DESCRIPTION

       gchem3d is a small chemical viewer application, which can show several chemical file formats.

OPTIONS

       The following options are accepted:

       -b COLOR, --bgcolor=COLOR
	   Use the given color as background color.  COLOR can be one of "black" (default), "white", "#rrggbb" (don't forget to escape the "#"
	   character in the shell).

       -d MODEL, --display3d=MODEL
	   Choose how molecules are displayed.	MODEL can be one of "BallnStick" (default), "SpaceFill".

       -?, --help
	   Show application help options.

       --help-all, --help-*
	   Print all or just a group of help options. These options are not documented here. Instead see gtk-options(7) and gnome-options(7).

       -v, --version
	   Print gchem3d version information.

SEE ALSO

       gnome-options(7), gtk-options(7)

AUTHORS

       Jean Brefort <jean.brefort@normalesup.org>
	   Program author.

       Daniel Leidert <daniel.leidert@wgdd.de>
	   Manpage author.

COPYRIGHT

       Copyright (C) 2002-2007 Jean Brefort
       Copyright (C) 2004-2007 Daniel Leidert

       Permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 2 or any
       later version published by the Free Software Foundation.

gcu 0.12				      $Date: 2009-03-19 10:53:47 +0100 (jeu. 19 mars 2009) $					GCHEM3D(1)
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