creating variable using variable value as part of new variable name

Question

I'm trying to create a new variable using the value of an existing variable as part of the variable name.

filemsg"$word1"=" "

I've also tried

filemsg$word1=" "

filemsg${word1}=" "

on all attempts I get the following when that line executes,

cicserrors.sh[45]: filemsgCICS= : not found [No such file or directory]

Solution 1

Use eval:

filemsgCICS=foo
word1=CICS
eval "echo \"\$filemsg$word1\"" # => foo
eval "filemsg$word1=bar"
echo "$filemsgCICS" # => bar

but think twice if you really need it this way.

Another way in ksh93 is to use namerefs:

word1=CICS
nameref v=filemsg$word1
v="xxx" 
echo "$filemsgCICS" # => xxx

For even more nasty hacks like that look here.

Solution 2

export does this far more safely than does eval because there is no danger of it executing shell code following a shell token. But it does export the variables so you can take it as you will.

export "filemsg$word1= "

Solution 3

It's not POSIX, but in bash there's always printf -v, which prints not to standard output, but rather to whatever variable name follows -v:

x=foo; printf -v $x bar; echo $foo

Output:

bar

Solution 4

Try this

let filemsg"$word1"=" "

This may not be the best solution, but it has worked for me in the past.

View more solutions

Comments

[Stéphane Chazelas]

You may want to use hashes/associative arrays instead (or perl or other real programming language)

[Denis Loh]

@dazedandconfused: Naming variables on the fly is the sort of thing that will have programmers and code maintainers waiting for you in a dark alley for the purposes of beating you with surplus power cords. It's really not a best practice.

[MariusMatutiae]

I agree with @Satanicpuppy: it is a practice to discourage, in my opinion.

[G-Man Says 'Reinstate Monica']

OK, that lets you display the value of the variable, but the question asks how to create the variable (i.e., to assign / set the value).