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# 1  
Old 05-09-2011
Shell script question
Hello all,

I have a script that has the following lines of code followed by other lines of code.. I'm not quite sure about the syntax in line #2, specifically ":-" ..what operation does it perform?

export IA_DAYS=$2
export IA_DAYS=${IA_DAYS:-90}
export IAW_DAYS=77
export AC=${1:-RP}

Thanks for your time
# 2  
Old 05-09-2011
Code:
export IA_DAYS=${IA_DAYS:-90}

will attempt to assign the value in the IA_DAYS variable to IA_DAYS. If IA_DAYS is not defined/empty, then 90 is used. This technique is used to allow the variable to be set externally if the user desires, but ensures that it has a value.

In this particular case, it is used to set the value if $2 is not defined on the command line. It could also have been written:
Code:
export IA_DAYS=${2:-90}

Last edited by agama; 05-09-2011 at 11:53 PM.. Reason: Additional clarification
This User Gave Thanks to agama For This Post:
luft
# 3  
Old 05-10-2011
Thank you so much for that clear explanation!
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