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Why does IF loop behave differently in different shells

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# 1  
Old 04-11-2008
Why does IF loop behave differently in different shells
Hi , I have a script that compares two string and prints the larger string , This is an extract of a biggers script that i have.
Code:
#! /bin/ksh
DT_STRING_CMP=20081221223440
DT_STRING=20071221223440


 if [ $DT_STRING -ge $DT_STRING_CMP ]; then
                        echo "20081221223440"
                        fi
echo "Hello"

If i run it in Kshell ( my users default shell) i get output as Hello
if i run it in C hsell (my users default shell) i get output as 20081221223440 and Hello
Why is it so ?
# 2  
Old 04-11-2008
The C shell has a completely different syntax. It's weird if this works in the C shell at all.

Using csh for scripting is discouraged. If your users don't have ksh then make it run under /bin/sh (probably a good idea in any case). It has slightly more constrained syntax than ksh but this particular script should work without modification.
# 3  
Old 04-11-2008
The values are too large for ksh to be able to do a numberic comparison which is what gt -ge is doing.
# 4  
Old 04-16-2008
Is there a way to then compare such big numbers ?
# 5  
Old 04-16-2008
You can try a text compare:

Code:
 if [wiki] "$DT_STRING" > "$DT_STRING_CMP" || "$DT_STRING" == "$DT_STRING_CMP" [/wiki]; then

# 6  
Old 04-16-2008
Ksh93 has better support for large numbers than pdksh or ksh88
Code:
#!/bin/ksh93

typeset -F STR1=20081221223440
typeset -F STR2=20071221223440

if [ $STR1 -ge $STR2 ]; then
    print "greater than"
fi
if [ $STR2 -ge $STR1 ]; then
    print "less than"
fi

exit

or to use more "modern" ksh syntax
Code:
#!/bin/ksh93

float STR1=20081221223440
float STR2=20071221223440

if (( $STR1 > $STR2 )); then
    print "greater than"
fi
if (( $STR1 < $STR2 )); then
    print "less than"
fi

Last edited by fpmurphy; 04-16-2008 at 10:18 PM..
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