Perplexed By Error - Bash

[jbarnes8]

First of all, I know there is probably an easier way to do what I'm doing, i'm just playing around trying to learn some things. I don't necessarily want this to work I'm just really confused by the error here. I DONT WANT SOLUTIONS, I WANT REASONS

This is just a little script i tried to write to grab values from config files.
Here's the error first, then the config file and code is below.

jeremy:/usr/local/bin# ./getconfiguration /usr/local/etc/medman.config MEDIADIR
./getconfiguration: line 25: =/home/media/: No such file or directory

i see that it's looking for "=/home/media" (with the equals sign) but from what i see there is no call to anything that should be looking that directory. That's the value i'm trying to extract from the config file.


if have a config file

#/usr/local/etc/medman.config
MEDIADIR=/home/media

And here's the script (you can probably skip the error checking)

usage: getconfiguration <path to config file> <name of value to extract>

#!/bin/bash

#$1 config file         #i know i should rename these but i'm not trying to fix this script, just understand it
#$2 variable name

##########################ERROR CHECKING#########################
if [ -z $1 ]
then
        echo "Not enough arguments"
        exit 1
fi
if [ -z $2 ]
then
        echo "Not enough arguments"
        exit 1
fi

if [ ! -f $1 ]
then
        echo "No such file \"$1\""
        exit 2
fi
############################END ERROR CHECKING######################


$val=$(grep "$2=*" $1 | cut -d '=' -f 2)   #this is the line that produces the error (line 25)

echo $val                                           #not sure the best way to return this value but that's not the problem

exit 0

EDIT: Also what is the best way to return values from (what will be) a child process without printing them to the screen. the only way i really know how to do this is VAR=$(somecommand)

[Cabhan]

Alrighty. So here's what I think is happening:

The error is being caused by using "$val=", rather than "val=". "$val" means "the value of the val variable". Because val is unset, $val is nothing, so the line becomes:

=$(grep "$2=*" $1 | cut -d '=' -f 2)

And then, of course, the grep command returns "/home/media", resulting in the line reading:

=/home/media

Because this line is not anything special in Bash (it is not an assignment, conditional, loop, function, etc.), it assumes that this is a command you want to execute (particularly, there should be a directory "=" that contains a directory "home" that contains an executable file called "media"). Obviously, because this does not exist, you are getting this error.

I will also note that the regular expression being used in the grep statement is wrong. The way you have it, you are looking for the variable, followed by 0 or more equals signs. I suggest either removing the '*', or adding that you are looking for 0 or more characters after the '=' (which would require the addition of a "[a-zA-Z]".