topic Re: Problem with string Comparison in Operating System - Linux

Problem with string Comparison

mougli — Fri, 28 Jul 2006 14:29:07 GMT

Hi,

Sorry for such a basic question. But still don't seem to get this working.

I get a fiename as an argument to the script and based on the file name, I need to rename it with the date appended to it.

#!/bin/ksh

INFILE=$1
echo "The incoming filename is $INFILE"
DAYSTRING=`date +%Y%m%d`
TIMESTRING=`date +%H%M%S`
if [ "$INFILE" = "prod_h_datafile_???.txt" ]
then
echo "Match Found"
OUTFILE=${DAYSTRING}${TIMESTRING}_hvendr.sig
fi
echo "The outgoing filename is $OUTFILE"

The script seeems to be working fine if I remove the ??? from the if statement and add the actual number. But with the ???, the comparison always fails.

Please suggest.

TIA

Re: Problem with string Comparison

Jonathan Fife — Fri, 28 Jul 2006 14:43:57 GMT

ksh doesn't do regexp on strings like that.

If you do something like

if [ $(echo $INFILE | egrep -c "prod_h_datafile_???.txt") -gt 0 ]

then it should work.

Re: Problem with string Comparison

Jonathan Fife — Fri, 28 Jul 2006 14:48:59 GMT

actually that doesn't work...

Re: Problem with string Comparison

Jonathan Fife — Fri, 28 Jul 2006 14:51:17 GMT

egrep -c "prod_h_datafile...\.txt"

there we go :)

Re: Problem with string Comparison

mougli — Fri, 28 Jul 2006 14:53:53 GMT

Thanks!! It worked..

Re: Problem with string Comparison

mougli — Fri, 28 Jul 2006 15:22:15 GMT

Sorry. I think there is a problem with your answer. Now If I add similar comparison statements, it returns 0 for all of them and all the comparison are true..

Re: Problem with string Comparison

harry d brown jr — Fri, 28 Jul 2006 15:25:58 GMT

Try

if [ `echo ${INFILE} | grep "prod_h_datafile_[0-9]\{8\}\.txt$"` ]

live free or die
harry d brown jr

Re: Problem with string Comparison

James R. Ferguson — Fri, 28 Jul 2006 17:03:26 GMT

Hi:

Instead of using a regular expression with an 'if' use a 'case':

Re: Problem with string Comparison

James R. Ferguson — Fri, 28 Jul 2006 17:05:21 GMT

Hi:

Sorry, I clicked the wrong button!

Instead of using a regular expression with an 'if' use a 'case' statement. Thry this version of your script:

#!/usr/bin/ksh
INFILE=$1
echo "The incoming filename is $INFILE"
DAYSTRING=`date +%Y%m%d`
TIMESTRING=`date +%H%M%S`
case $INFILE in
prod_h_datafile_[0-9][0-9][0-9].txt )
echo "Match Found"
OUTFILE=${DAYSTRING}${TIMESTRING}_hvendr.sig
;;
* )
echo "NO match!"
;;
esac
echo "The outgoing filename is $OUTFILE"

...

Regards!

...JRF...

Re: Problem with string Comparison

Dennis Handly — Fri, 28 Jul 2006 19:14:55 GMT

To do pattern matching in sh/ksh you need to use [[ ]]:
if [[ "$INFILE" = prod_h_datafile_???.txt ]]

Note you can't quote the pattern.

Re: Problem with string Comparison

mougli — Mon, 31 Jul 2006 10:46:13 GMT

Thanks Dennis. It worked.

Regards..

Re: Problem with string Comparison

mougli — Mon, 31 Jul 2006 10:46:55 GMT

Thanks Dennis. It worked. But is there something missing without the quotes??

Regards..

Re: Problem with string Comparison

Dennis Handly — Sun, 14 Aug 2011 23:11:43 GMT

>But is there something missing without the quotes??

One day I was fiddling with a script and it had [[ ]] instead of [ ] and I didn't know why it failed. I assumed it was string comparison. But it is pattern matching and by experience, it doesn't allow quotes. Probably assumes the they are part of the pattern? That's why I warned you.

If you want to quote an embedded space, use "\".