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Home >Unix > Korn shell scripting If constructs AND, OR, &&, ||

Every unix script dialects has its syntax differences. In if statements to test several conditions I try to use the syntax that I can export to other Unix/linux environments. Sometimes, small syntax differences affect the real execution. I did learn to be very careful, for example on HP-UX B.11.23 you do not always get back an error when the if do not work at all.

#file if_construct.ksh
#tested on  HP-UX B.11.23 U ia64 



v1="Contract"
v2="CustomerA"

####### AND

## checking conditions with AND ... but it behave differently then &&  ... check the note
if [ $v1 = "Contract" ] AND [  $v2 = "Customer" ] 
then
echo " all conditions have been be obliged => syntax AND"
fi



## checking conditions with double ampersand &&
if [ $v1 = "Contract" ] &&  [  $v2 = "Customer" ] 
then
echo " all conditions have been be obliged => syntax &&"   
fi

####### OR 
## checking conditions with OR 
if [ $v1 = "Contract" ] OR [  $v2 = "Customer" ]  
then
echo " At least one of the variables contain requested value => syntax OR"
fi

## checking conditions with double pipe ||
if [ $v1 = "Contract" ] || [  $v2 = "Customer" ]  
then
echo " At least one of condition has been respected => syntax ||"   
fi

I always try to use double ampersands (&&) for AND, double pipe ( || ) for OR, but I do assume they are the same, like in others programming languages. Please note, in Unix Hp, Korn Shell, OR behaves differently II. As a matter of fact, in the if AND example seems true only if just the first variable is true: If you try the following example, the echo witching the if will be executed. I do not know why, but at the moment I use always || ...

#file if_construct.ksh
#tested on  HP-UX B.11.23 U ia64 
v1="Contract"
v2="Store"
## checking conditions with AND ... but it behave differently then &&  ... check the note
if [ $v1 = "Contract" ] AND [  $v2 = "Customer" ] 
then
echo " all conditions have been be obliged => syntax AND"
fi

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