How to dynamically set a variable name in shell script?

Question

I am looking for a sh equivalent of the following (yes, really.)

#!/bin/bash exe1='filepath' n=1 var=exe${n} echo ${!var} 

Where the echo should output filepath. I want to use plain sh.

I have already played around with the code a lot, but I didn't manage to get the output right so far.

I want to achieve an array-like structure, I'd just want to iterate over the variable name for a known number of variables using a loop.

For the array I found Arrays in a POSIX compliant shell but I'm still looking for the answer to the question for curiosity ;)

Answer 1

An equivalent sh script to what's presented in the question:

#!/bin/sh exe1='filepath' n=1 var=exe$n eval "echo \"\$$var\"" # or: eval 'echo "$'"$var"'"' 

The eval line will evaluate the given string as a command in the current environment. The given string is echo \"\$$var\", which, after variables have been expanded etc., would become echo "$exe1". This is passed to eval for re-evaluation, and the command prints the string filepath.

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You also mention arrays. It is true that the POSIX sh shell does not have named arrays in the same sense that e.g. bash has, but it still has the list of positional parameters.

With it, you can do most things that you'd need to do with a list in the shell.

For example,

set -- 'filepath1' 'filepath2' 'filepath3' for name in "$@"; do # or: for name do echo "$name" done 

which is the same as just

for name in 'filepath1' 'filepath2' 'filepath3' do echo "$name" done 

Since I'm usure of what it is you're trying to achieve, I can't come up with a more interesting example. But here you have an array-like structure that you iterate over. Why you'd want to iterate over names of variables is still not clear.

Answer 2

If you want to iterate over a number of files (implied from exe1=filepath in example) does a simple for loop work?

final_file is the variable holding the last file which matches the file_pattern - replicating bash's ${!var} (last argument referencing).

 #/bin/sh final_file='' file_pattern='*.txt' for f in $file_pattern do echo $f final_file=$f done echo $final_file