How Can I Execute Environment Variables in Shell Script? [duplicate]

Question

I have 2 files. One is list file named envlist. Another one is shell script file named test.

In envlist(list file), there's the environment variable list as below ;

setup_top
CFG

those are already declared as the environment variable.

(So when I type cd $setup_top or cd $CFG in command, it works well)

And in test(shell script), there's the code as below ;

#!/bin/bash

dir=$(<$env/envlist)     # $env is another environment variable I declared.
for i in ${dir[*]}
do
     cd $i               # I think this line is a matter.
     echo "------------------"
     sleep 2
done

When I executed this shell script, I got the error as below;

./test: line 6: cd: setup_top: No such file or directory
----------------------------
./test: line 6: cd: CFG: No such file or directory
----------------------------

reading envlist file line by line seems to work well, but cd command seems not to work.

How can I fix the shell script code to work fine?

If setup_top and CFG are relative paths, you need to include a cd .. at the end of your loop. — Jann Poppinga
– Jann Poppinga, Commented Oct 21, 2020 at 8:41

Stéphane Veyret · Accepted Answer · 2020-10-21 08:34:36Z

0

Actually, you need to transform $i into the name of the variable, then read $varname. If the shell would support this, you should write cd $$i. Unfortunately, this will not work, because $$ gives the current PID.

As suggested by @Biffen, you should use shell variable substitution:

cd ${!i}

Previous answer, using dangerous eval instruction:

eval cd \$$i

Note: eval is a dangerous instruction. Use it only if you are sure of the content of your files (not files provided by untrusted users).

answered Oct 21, 2020 at 8:34

Stéphane Veyret

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5 Comments

Satthew Seong Hun Moon Over a year ago

Thank Veyret for answering me. You gave me two answers. Unfortunatly I had same wrong answer after changing the line. Only two "------------" are the things I got from terminal.

Satthew Seong Hun Moon Over a year ago

when I tried Bourne-Again Shell Script, ASCII text executable, it failed. But When I tried Bourne-Again Shell Script, UTF-8 unicode text executable, it works!!! Thanks!!!!

Biffen Over a year ago

@SatthewSeongHunMoon What else do you expect?! cd doesn’t print anything.

Satthew Seong Hun Moon Over a year ago

Nah What I wanted to say was When I execute that line, It shoild be moved to $setup_top or $CFG. But it didn't move at all

Biffen Over a year ago

@SatthewSeongHunMoon How did you verify that? You can’t ‘see’ the working directory changing.

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