shopt -s nullglob Post: 302254561

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Top Forums Shell Programming and Scripting shopt -s nullglob Post 302254561 by msb65 on Tuesday 4th of November 2008 05:53:14 PM

11-04-2008

Registered User

shopt -s nullglob

Hi,

I am using BASH. In a directory there are files that match either of the following 2 patterns: [AST]*.L1A_[GL]AC* or S*.L1A_MLAC*

I would like to write a script that will include a for loop, where for each file in the directory, a certain function will be performed. For example:

for FILE in [AST]*.L1A_[GL]AC* S*.L1A_MLAC*; do
echo $FILE
done

The content of the directory will be random, and there are 3 potential scenarios: 1) Files of both patterns exist in the directory, 2) Only files of the 1st pattern exist, 3) Only files of the 2nd pattern exist. The last two scenarios are problematic as one of the patterns won't be matched, resulting in my script behaving oddly.

- I believe the way around this is to use the shopt -s nullglob option. Does anyone have any other ideas?

- MAIN QUESTION: Where in the code should I put the shopt -s nullglob and shopt -u nullglob? Of course the shopt -s nullglob should be set immediately before the the beginning of the for loop. But, can the shopt -u nullglob be immediately after the beginning of the for loop (ie):

shopt -s nullglob
for FILE in [AST]*.L1A_[GL]AC* S*.L1A_MLAC*; do
shopt -u nullglob
echo $FILE
done

OR after the conclusion of the for loop (ie):

shopt -s nullglob
for FILE in [AST]*.L1A_[GL]AC* S*.L1A_MLAC*; do
echo $FILE
done
shopt -u nullglob

The reason I ask is because I will of course have more complicated code within the for loop, and only want the shopt nullglob command to affect the pattern matching when calling the for loop.

Thanks for your help.

Mike

msb65

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checkbashisms

CHECKBASHISMS(1)					      General Commands Manual						  CHECKBASHISMS(1)

NAME

       checkbashisms - check for bashisms in /bin/sh scripts

SYNOPSIS

       checkbashisms script ...
       checkbashisms --help|--version

DESCRIPTION

       checkbashisms, based on one of the checks from the lintian system, performs basic checks on /bin/sh shell scripts for the possible presence
       of bashisms.  It takes the names of the shell scripts on the command line, and outputs warnings if possible bashisms are detected.

       Note that the definition of a bashism in this context roughly equates to "a shell feature that is not required to be supported  by  POSIX";
       this means that some issues flagged may be permitted under optional sections of POSIX, such as XSI or User Portability.

       In  cases  where  POSIX	and  Debian  Policy  disagree, checkbashisms by default allows extensions permitted by Policy but may also provide
       options for stricter checking.

OPTIONS

       --help, -h
	      Show a summary of options.

       --newline, -n
	      Check for "echo -n" usage (non POSIX but required by Debian Policy 10.4.)

       --posix, -p
	      Check for issues which are non POSIX but required to be supported by Debian Policy 10.4 (implies -n).

       --force, -f
	      Force each script to be checked, even if it would normally not be (for instance, it has a bash or non POSIX shell shebang or appears
	      to be a shell wrapper).

       --extra, -x
	      Highlight lines which, whilst they do not contain bashisms, may be useful in determining whether a particular issue is a false posi-
	      tive which may be ignored.  For example, the use of "$BASH_ENV" may be preceded by checking whether "$BASH" is set.

       --version, -v
	      Show version and copyright information.

EXIT VALUES

       The exit value will be 0 if no possible bashisms or other problems were detected.  Otherwise it will be the sum of the following error val-
       ues:

       1      A possible bashism was detected.

       2      A file was skipped for some reason, for example, because it was unreadable or not found.	The warning message will give details.

SEE ALSO

       lintian(1).

AUTHOR

       checkbashisms  was originally written as a shell script by Yann Dirson <dirson@debian.org> and rewritten in Perl with many more features by
       Julian Gilbey <jdg@debian.org>.

DEBIAN
								 Debian Utilities						  CHECKBASHISMS(1)