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what does ${VARIABLE:-0} stand for?

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# 1  
Old 12-21-2009
Question what does ${VARIABLE:-0} stand for?
Hi all,

During reading the code, i met such expressment in a KSH script. I can not figure out what does this mean and don't know how to search it in the web. Could you please check below snippet and let me know what does this mean in a shell script:

Code:
VARIABLE=1
if [ ${VARIABLE:-0} -ne 1 ]; then
   . /bin/another_shell.sh
fi

I also met similiar situation before like:
Code:
${VARIABLE:-1}
${VARIABLE:-0/}

(may not exaclty like it, but there is definitely a slash at the end)

Thanks in Adv.
Last edited by zaxxon; 12-21-2009 at 03:44 AM.. Reason: use code tags please
# 2  
Old 12-21-2009
Hi.

It means:

Quote:
${parameter:-word}
Use Default Values. If parameter is unset or null, the expansion of word is substituted. Otherwise,
the value of parameter is substituted.
It's described in the man page.
# 3  
Old 12-21-2009
Explanation:-

Code:
${parameter-default}, ${parameter:-default}
If parameter not set, use default.

echo ${username-`whoami`}
# Echoes the result of `whoami`, if variable $username is still unset.

${parameter-default} and ${parameter:-default} are almost
equivalent. The extra : makes a difference only when parameter has been declared,
but is null.

SmilieSmilieSmilieSmilie
# 4  
Old 12-21-2009
Scttn, ahmad.diab,

Great thanks for your clear explanation...
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