Bash script

lenzj · 08-23-2006, 01:51 PM

I'm trying to write a bash script function that will either execute a command or echo the command to the console depending on a variable test.

Code:

#!/bin/bash
execD () {
if [[ "$Debug" == "On" ]] 
    then
	echo "$*"
    else
	$*
    fi
}
Debug='On'
execD "echo \"Debug = $Debug\" | wc -w"
Debug='Off'
execD "echo \"Debug = $Debug\" | wc -w"

Output of above bash script.

Code:

echo "Debug = On" | wc -w
"Debug = Off" | wc -w

What I was intending the second line of output to be is the number 3, but instead bash assumes the pipe and wordcount command are part of the text to be echoed. I've found that if I replace the $* in the else section with /bin/bash -c "$*" then it works. It seems like a less elegant and less efficient way to do this however. Is there a way to do this without shelling out to another bash environment?

Thanks in advance,
Jason

KenJackson · 08-23-2006, 02:49 PM

Try replacing

Code:

$*

with

Code:

        eval "$*"

zhangmaike · 08-23-2006, 03:01 PM

FYI: bash ignores special characters like | when they come from environment variables. This makes a good deal of sense. If this weren't the case, a person passing a parameter like \" to any otherwise working script would break that script, because that script is suddenly missing an ending quote.

eval will force bash to evaluate those characters regardless.

lenzj · 08-24-2006, 11:36 AM

That worked like a charm. I missed the eval command somehow when I was looking into this. I guess the language engineers knew how to protect me from myself! Thank you both for the responses.