bash: problem with [sets]

[David selby <debian@pusspaws.net>]

My bash masterpeice is almost complete ... I have one last problem that 
no matter how many "" or '' I use I cannot get around.

I need to use an if...then construct to check that my 4 digit date field 
is 4 numerical digits.This is for error checking.  I thought [sets] was 
the way to go ....

if [ $fourdig = [0-9][0-9][0-9][0-9] ]; then ......

I have tried '[0-9]' "[0-9]", straight [0-9]. Interestingly no matter 
what I do in [sets] as a comaparison it is invalid in the if...then 
construct. It has occured to me that perhaps [sets] are not allowed as a 
conditional test.

If this is the case, how can I test a string ?

Dave








#!/bin/sh

# Remind script v1.0 23rd June 2003 Dave Selby


calender=/mnt/archive/remind/calender/
toX=/mnt/archive/remind/toX/
mmddfile=/mnt/archive/remind/mmdd

header='\nThis is a reminder message from "remind" v1.0 23rd June 
2003\nTo change the calender cd /mnt/archive/remind/calender\n\n'



# Displays a remind screens in eye catching red !
remindscreens ()
{

# Scans the /mnt/archive/toX dir, displays all remind screens
for toXfiles in $(ls $toX); do

   echo -e -n $header'File :'$calender$toXfiles'\n\n'$(cat 
$toX$toXfiles) | xmessage -fn 9x15 -center -buttons OK,Print,Delete 
-default OK -bg red -file -
   case $? in
       102) echo -e -n '\n\n\n'$header'File 
:'$calender$toXfiles'\n\n'$(cat $toX$toXfiles) | lpr;;
       103) rm $toX$toXfiles;;
   esac
done
}


nowmmdd=$(date '+%m%d')

# Get value of mmdd if it exists, else set it to 0101
if [ -e $mmddfile ]; then
   oldmmdd=$(cat $mmddfile)
else
   oldmmdd="0101"
fi


# Abort if this is not the first run of the day
if [ ! $oldmmdd -eq $nowmmdd ]; then
      
# Scans $calender, if files are in date range, copy them to $toX
for calfile in $(ls $calender); do

   fourdig=${calfile:0:4} # Strip off date
   if [ $fourdig -gt $oldmmdd ] && [ $fourdig -le $nowmmdd ]
   then
        cp $calender$calfile $toX
   fi

done

# Update mmddfile to now, ready for tomorrow !
echo $nowmmdd > $mmddfile
chmod a=rwx $mmddfile

remindscreens &

fi