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up vote 4 down vote favorite
2

I have the following:

#!/bin/sh

n=('fred' 'bob')

f='n'
echo ${${f}[@]}

and I need that bottom line after substitutions to execute

echo ${n[@]}

any way to do this? I just get

test.sh: line 8: ${${f}}: bad substitution

on my end.

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2 Answers

up vote 9 down vote accepted

You can do variable indirection with arrays like this:

subst="$f[@]"
echo "${!subst}"

As soulmerge notes, you shouldn't use #!/bin/sh for this. I use #!/usr/bin/env bash as my shebang, which should work regardless of where Bash is in your path.

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This worked beautifully! Thanks! –  Andy Dec 8 '11 at 17:57
3  
+1 Indirect expansion is far less of a bug magnet than eval. –  Gordon Davisson Dec 8 '11 at 23:24
up vote 1 down vote

You could eval the required line:

eval "echo \${${f}[@]}"

BTW: Your first line should be #!/bin/bash, you're using bash-specific stuff like arrays

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+1 if I had any votes remaining today. Can you explain what eval does? –  jman Dec 8 '11 at 17:53
 
eval just evaluates the parameter string as a command. –  Andy Dec 8 '11 at 17:58
 
I do not understand why people keep downvoting without providing any feedback? –  soulmerge Dec 9 '11 at 0:21
 
I didn't downvote, but in general things like eval should be avoided in most languages if there is an alternative. They sometimes introduce subtle bugs or security risks. –  Michael Hoffman Dec 22 '11 at 21:28

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