POSIX Regular Expressions / Character Classes

 Computers and Networking
Sep 072010
 

POSIXExpressions-CharacterClasses

#!/bin/bash

#Make sure there are two arguments entered on the command line.
if [ $# -ne 2 ]
then
    echo “Error in $0 – Invalid Argument Count”
    echo “Error in $0 – Need two arguments”
    echo “Example Syntax: $0 input_file output_file”
    exit
fi

#Check if a file exists
if [ ! -f $infile ]
then
echo “Input file [$infile] not found – Aborting”
exit
fi

Shell script using case statement to filter user input

 Computers and Networking
Sep 072010
 

It’s possible to use even more complicated syntax with regular expressions:

I used this in my FTP script for safety surveillor.

case “$1? in
+(start|run) ) /usr/app/startup-script ;;
@([Ss])top ) /usr/app/stop-script ;;
esac

?(pattern1 | pattern2 | … | patternn)
zero or one occurrence of any pattern

*( pattern1 | pattern2 | … | patternn)
zero or more occurrences of any pattern

@( pattern1 | pattern2 | … | patternn)
exactly one occurrence of any pattern

+( pattern1 | pattern2 | … | patternn)
one or more occurrence of any pattern

!( pattern1 | pattern2 | … | patternn)
all strings except those that match any pattern