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Calling a variable from a variable.

 
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# 1  
Old 03-18-2013
Calling a variable from a variable.
Hi everyone,

Is it possible to set a variable that calls another variable?

I.E.
Code:
SCRIPT=MY_SCRIPT.ksh ${VAR5}

${VAR5} is set earlier in the script, and I want to be able to call this when setting the ${SCRIPT} variable.

I hope this makes sense.

Thanks for your help.
# 2  
Old 03-18-2013
Wrap it in double quotes and use eval
Code:
SCRIPT="./MY_SCRIPT.ksh ${VAR5}"

eval "$SCRIPT"

This User Gave Thanks to Yoda For This Post:
jimbojames
# 3  
Old 03-20-2013
Quote:
Originally Posted by Yoda
Wrap it in double quotes and use eval
Code:
SCRIPT="./MY_SCRIPT.ksh ${VAR5}"

eval "$SCRIPT"

Not exactly. When we look at:
Code:
SCRIPT="./MY_SCRIPT.ksh ${VAR5}"
eval "$SCRIPT"

What is being suggested here is probably not what is wanted.

If the intent is to expand $VAR5 at the time SCRIPT is defined, then the eval is not needed when script is invoked to run MY_SCRIPT.
Code:
SCRIPT="./MY_SCRIPT.ksh ${VAR5}"
eval "$SCRIPT"

But, if the intent is to have the shell expand $VAR5 at the time that $SCRIPT is invoked, then single quotes (rather than double quotes) need to be used when SCRIPT is defined.

As an example, look at the following sequence of commands:
Code:
VAR5=initial
SCRIPT="echo $VAR5"     # Note the double quotes
VAR5=middle
$SCRIPT                 # produces: initial
"$SCRIPT"               # produces: echo initial: not found
eval "$SCRIPT"          # also produces: initial
SCRIPT='echo $VAR5'     # Note single quotes: VAR5 is currently set to middle
VAR5=final
$SCRIPT                 # produces: $VAR5
"$SCRIPT"               # produces echo $VAR5: not found
eval $SCRIPT            # produces: final

This User Gave Thanks to Don Cragun For This Post:
jimbojames
# 4  
Old 03-20-2013
eval is dangerous. Why not save just the script name, and feed the variable into it later?
This User Gave Thanks to Corona688 For This Post:
jimbojames
 
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