[SOLVED]How to compare two string variables - Bash Scripting

[bots4ever]

Greetings fellow Mageia users!

I am trying to customize my conky script and I ran into some challenges (technical things that are way over my head at the moment). Basically what I wanted to do is to create an exec command for my conky to run this script that I am working on.

The thing is, my laptop has 2 heads - an Intel HD4000 and an ATI Radeon 7670M card. I would like my conky to display the temperature of my Radeon card if it is selected and display something like "disabled" or something if I decide to use my Intel HD4000 graphics. Here is the script:

Code: Select all

value1="ERROR - X needs to be running to perform AMD Overdrive(TM) commands"
command1=$(aticonfig -q --od-gettemperature > output)
value2=$(cat output)
if [$value2 -eq $value1]
  then
    echo $value2
  else
    $command1
fi


The script is really basic but to give you an overview...
"value1" is a static variable text
"command1" is the command to extract the information, particularly the temperature, of my ATI Card and outputs the details to a textfile in the same directory where the shell script is saved (later i'll just use grep to drill down the exact data I wanted to extract).
"value2" to get the value of the information contained in "output" file from the previous command.

I used an IF THEN ELSE statement for this one and I am always getting an error

line 4: [ERROR: command not found

I substituted "-eq" with "=="; played a lot with namespaces [ if (argument 1) (argument 2) ] vs [if (argument 1) (argument 2)] and many other spacing combinations; I also tried [ if (argument1) (argument2) then ] instead of placing "then" as listed on the code

By the way, if I run aticonfig command when I'm using my Intel HD4000, I get the this message

ERROR - X needs to be running to perform AMD Overdrive(TM) commands

.

My bash version is

GNU bash, version 4.2.49(2)-release (x86_64-mageia-linux-gnu)

by running

Code: Select all

bash --version

And lastly, I am using Mageia 4 64bit dualbooting with CentOS 6.5 64bit if that matters.

Please ask questions if there is something I missed.

[ITA84]

The correct syntax to compare strings would be

Code: Select all

if [ "$value1" = "$value2" ]
then
    ...
else
    ...
fi

By the way, just using $command1 in the else branch would probably accomplish nothing, as $command1 would be replaced by the output of aticonfig... (which might be empty since you redirect stdout to file).

[doktor5000]

I can only recommend you to read some of the examples in http://mywiki.wooledge.org/BashPitfalls.

Three recommendations:
- -eq, as any other of the logical operators can only compare integers, not strings, for strings you can only use = or != [to put it simple]
- don't use simple test command "[" but use the shell builtin "[[" instead - always!
- for such simple two-case comparisons don't use if .. then .. else but only use the above mentioned super-test, hence for your case I'd use

Code: Select all

[[ "$value1" = "$value2" ]] && { echo $value2 ; } || { $command1 ; }

Not looked closer at your script, but instead of that you should even be able to simplify it using something like this:

Code: Select all

FOO="${BAR:-new}"

means that use $BAR if nonzero, otherwise set it to "new"

[bots4ever]

Sorry it took me a while to respond back. I got into more noob problems than I originally thought i'd encounter with my Conky project.

Now, my script works as intended and for your reference, here it is.

Code: Select all

sample="aticonfig: No supported adapters detected"
aticonfig --adapter=0 --od-gettemperature > temp 2>&1
output=$(<temp)
set -- $output
if [ "$output" == "$sample" ];
then echo "Disabled";
else aticonfig --adapter=0 --od-gettemperature | grep -e "Sensor 0" | cut -b 37-43;
fi


Thank you ITA84 for pointing that out. I followed your suggestion.

Thank you doktor5000. I will certainly take a look at the link you provided once I started getting serious with my shell scripting lessons.

With this I am marking this thread closed and renaming into a more appropriate topic so other newbie users can benefit. Thanks again!