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Shell Programming and Scripting

Understanding a Simple Shell Script

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# 1  
Old 12-06-2009
MySQL Understanding a Simple Shell Script
Code:
#! /usr/bin/ksh
old=$1
new=$2
for file in *.$old ; do
     mv $file ${file%$old}$new
done
exit 0

This script i got from the forum. script changes the extension of the files say example
a.txt to a.doc
b.txt to b.doc
c.txt to c.doc
d.txt to d.doc

this scipt works fine but i am not getting the concept of ${file%$old}$new how it works
please help me to undestand the logic

Thanks
Vijay
Last edited by DukeNuke2; 12-06-2009 at 02:53 PM.. Reason: please use code tags!
# 2  
Old 12-06-2009
hello vijay ..
${parameter%pattern}: The 'pattern' is anchored to the end of 'parameter'. The result of the expansion is the expanded value of 'parameter' with the shortest match deleted.
so the two extensions are provided in the cmdline and the files are renamed (aka mv) from their older names to newer names(with newer extensions).
Hope this make things clear.
Smilie
regards.
# 3  
Old 12-06-2009
See Parameter expansion
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