Shell Programming and Scripting

Hi all,

Am trying to execute a loop but having some troubles...
Files that will be query'd use the Julian date (eg: cpu032, cpu365) in their naming convention.

I'm a little lost how to maintain the three character format of the numeric portion of the file name while cycling backwards(or forwards for that matter) in a loop.

Something similar to the following:

Code:

xstart=`date '+%j'`
xend=`expr $xstart - 30`

while [ $xstart -gt $xend ] ; do

  echo $xstart
  xstart=`expr $xstart - 1`

done

If $xstart begins at 032 (1-Feb) and $xend becomes 002 (2-Jan) then I should see...
032
031
030
029
...
004
003
002

Unfortunately I'm not - and is only displaying the significant digits.
Is there any way around this??

Here's one that might help:

xstart=`date '+%j'`
xend=`expr $xstart - 30`
while [ $xstart -gt $xend ] ; do
if [ $xstart -lt 10 ]; then
echo 00"$xstart"
elif [ $xstart -lt 100 ]; then
echo 0"$xstart"
else
echo $xstart
fi
xstart=`expr $xstart - 1`
done

It's not the prettiest, but it does the trick.

Thanks seismic_willy,

I've already use the same techique in another script for reporting stats, but thought that there may have been another way.

Again, thanks.

With ksh, just use "typeset -Z3 xstart" at the top of the script. Then ksh will maintain the leading zeros.

Thanks Perderabo,

Is there a similar way to do the same in `bash` ?

Bash does not support that option to typeset.
Also, if you're using a Linux-based OS, you most likely have PDKSH installed, instead of ksh. Most versions of pdksh do not support that either - only the "real" ksh can be trusted...

Good news though! You can get David Korn's KSH 93 from here:
http://www.research.att.com/sw/download/

Using AT&T's package is a bit of a pain, but it's worth it.

If you cannot use typeset, you can format it with awk:

Code:

#!/bin/sh

xstart=`date '+%j'`
xend=`expr $xstart - 30`

while [ $xstart -gt $xend ] ; do

  xname=`awk 'BEGIN {printf "%3.3d",'$xstart';exit}'`
  echo $xname
  xstart=`expr $xstart - 1`

done