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Significance of ':-' while accessing a variable

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# 1  
Old 01-20-2013
Significance of ':-' while accessing a variable
Hi

I was trying to understand what ':-' means when used with variables

Code:
 
echo ${x:-10}
 
if [ "${OSH_compileFlag:-}" = "1" ]

Thanks
# 2  
Old 01-20-2013
I do not know if -10 is a valid argument, i thought it needs a positive integer.

Code:
echo ${x:a:b}
a=start
b=number to select

Code:
x=1234567890
echo ${x:2}
34567890

echo ${x:2:4}
3456

# 3  
Old 01-20-2013
The above is actually creating the variable with value 10 and the variable exists for only one time use. The second attempt to access the variable says it isn't defined (blank value)
# 4  
Old 01-20-2013
It means:
Code:
${parameter:-word}
    Use Default Values. If parameter is unset or null, the expansion of word shall be substituted; otherwise, the value of parameter shall be substituted.

See Shell Command Language: 2.6.2 Parameter Expansion
These 2 Users Gave Thanks to Scrutinizer For This Post:
karthikeayan zulfi123786
# 5  
Old 01-20-2013
Many Thanks for mentioning the reference Smilie
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