Simple Shell script question

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August 19th, 2004, 02:07 PM

Timtro

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Simple Shell script question

Hi guys. Please forgive me as this is my first script of this nature. My previous scripting experience is limited to input file generation and auto execution of scientific software.

I have a directory full of stuff to rename. For such, I have written the following script:

Code:

num=0
basename="5FFA45-"

for curf in *
do	
	ftmp=`echo $basename$num`
	echo $ftmp         #This is where I will be putting the 'mv' command
	let "num += 1"
done

Looking at this, my intensions are clear for the most part. I need something that will go through all the files, and will rename them with a common base-name, and add a number that cooresponds to the order in the directory listing.

My problem is that I want to be able to preserve file extensions. How can I do this?

August 19th, 2004, 02:49 PM

jim mcnamara

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Code:

#!/bin/ksh             
let count=0
basename="5FFA45-"

for file in *
do
  file_ext=${file#*.*}  
  echo $basename"$count".$file_ext  
  # change the above line to: mv $file $basename"$count".$file_ext
  let count=$count+1
done
exit

-- this will work on files with a single . and with no spaces in their names.

August 19th, 2004, 03:31 PM

Timtro

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Hmmm. That looks interesting. I'm not sure that I understand some of it.

What do you think of this?

Code:

#! /bin/bash
#
#  A simple scipt to rename a bunch of files
#  in a directory, such that the extensions
#  are preserved.
#
#		by Timothy A.V. Teatro
#
#		Date: 08.19.04


num=0
basename="5FFA45-"

for curf in *
do	
   ext=`echo $curf | awk -F"." '{ print $2 }'`
	ftmp=`echo $basename$num.$ext`
	mv "$curf" "$ftmp"
	let "num += 1"
done

Can you explain in a little more depth exactly what that line does? I am intruiged by it.

Thank you very much for replying.

August 19th, 2004, 04:55 PM

jim mcnamara

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Code:

file_ext=${file#*.*}

removes everything up to and including the dot in the variable: file. It gets the extension just like your awk statement does, except it's a builtin korn/bash substitution function.

and..

Code:

let "num += 1"
should be:
let num+=1

lose the spaces spaces; you don't really need the quotes.

August 27th, 2004, 02:21 AM

guggach

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timtro
did you already try to read&&write sh-scripts ?
i know, you && a lot other people like 'ksh' and 'ksh'
is still NOT standard, the only really standard is 'bourne'

your script is very dangerous, you don't check the existence of
the new file...

NOTA:
- basename is a unix-cmd, don't use it, could be very confusing.
- don't abuse of ", use it when it's needed.

try something like:

Code:

#!/usr/bin/sh
num=0
newname=5FFA45-

for curf
do	
	ftmp=`echo $curf | sed 's/^.*\(\..*\)/\1/`
        [ x$tmp = x ] && continue # extention not found
	[ -f $newname$num$ftmp ] && continue # file exists
        mv $curf $newname$num$ftmp

	num=`expr $num + 1`
        # or better num=`echo $num + 1 | bc`
        # it's faster by large op
done

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