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Does Filename Match Pattern

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# 1  
Old 12-16-2008
Does Filename Match Pattern
Hi,

I am writing a BASH script. I have a list of files and I would like to make sure that each is of a specific pattern (ie [AT]*.L2). If not I would like to remove that file. How do I test whether a filename matches a given pattern?
Thanks a lot.

Mike
# 2  
Old 12-16-2008
Use the ls command and check its return code

Code:
ls -l [AT]*.L2  > /dev/null 2>&1

# 3  
Old 12-16-2008
Thank you for the reply! What does the "&1" indicate? Are you outputting the standard error of the ls statement?

Mike
# 4  
Old 12-16-2008
Quote:
Originally Posted by msb65
I am writing a BASH script. I have a list of files and I would like to make sure that each is of a specific pattern (ie [AT]*.L2). If not I would like to remove that file.

Code:
shopt -s extglob
rm !([AT]*.L2)

Quote:
How do I test whether a filename matches a given pattern?

Code:
case $filename in
     [AT]*.L2) printf "%s matches\n" "$filename" ;;
     *) printf "%s does not match\n" "$filename" ;;
esac

# 5  
Old 12-16-2008
Quote:
Originally Posted by msb65
Thank you for the reply! What does the "&1" indicate? Are you outputting the standard error of the ls statement?

Mike
The '&1' redirects the output of stderr to the output of stdout, which in this case is /dev/null. It could have been easily written as

Code:
ls -l [AT]*.L2  > /dev/null  2> /dev/null

The redirection of the output supresses any results or error messages. In this case you only care about the return code.
# 6  
Old 12-16-2008
Quote:
Originally Posted by cfajohnson

Code:
shopt -s extglob
rm !([AT]*.L2)


Code:
case $filename in
     [AT]*.L2) printf "%s matches\n" "$filename" ;;
     *) printf "%s does not match\n" "$filename" ;;
esac

Hi cfajohnson,

Yes I was thinking about doing that. However, the pattern that I would like to match is condition dependent. I would like to do something like this:

Code:
if [ $START_LEVEL = 0 ]; then
        PATTERN_ARRAY=('[AT]*.L0_LAC' 'MOD00.[AP]*.PDS')
elif [ $START_LEVEL = 1 ]; then
        PATTERN_ARRAY=([AST]*.L1A_[GL]AC* S*.L1A_MLAC*)
elif [ $START_LEVEL = 2 ]; then
        PATTERN_ARRAY=([AST]*.L2_[GL]AC* S*.L2_MLAC*)
elif [ $START_LEVEL = 3 ]; then
        PATTERN_ARRAY=([AST]*_*_*.L3)
fi

for ENTRY in *; do
     for PATTERN in ${PATTERN_ARRAY[@]}; do
          case $ENTRY in
               $PATTERN)
               echo 'Entry matches pattern'
               ;;
               *)
               echo 'Entry does NOT match pattern'
               ;;
          esac
     done
done

However, the shell appears to be performing the pattern matching in if statements. Is there a way to get around that? Thank you.

Mike
# 7  
Old 12-16-2008

The shell performs filename expansion anywhere you have an unquoted pattern. If you do not want it expanded, quote it.

You have unquoted patterns in your array assignments and in the array expansion.
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