[SOLVED] Unix-style program options (--option) in Bash?

[jesushero]

Hello, I'm writing a bash script and I want to implement some of the usual unix-style options, given to programs in the manner of:


program --option1 --option2

The obvious way is to use $1, $2 ... $34534 for any string arguments given, and predict all possible combinations of options and what to do.

This is fine for 3-4 options. For a large number of options however it results in a huge script, most of which simply deals with all possible combinations of options.

Is there any smarter way of doing this in a Bash script? Like, just adding a single line of code regarding each option, no matter in what order options are given or if some are missing or something like that?

If not, is there a way in C/C++? I'm not that comfortable with C but I'd be willing to go that way if it's necessary.

[weresheep]

Hello,

Here is the method I use for program options for shell scripts...



for i in $* ; do
case "$i" in
-t ) RETAG=1 ;;
-m ) MP3=1 ;;
-r ) REVERSE="-r" ;;
. ) MUSICDIR=$(pwd) ;;
* ) MUSICDIR="$i" ;;
esac
done


The $* in the for loop expands to all the provided options.

The * ) in the switch (case) statement is like C's default case. It means anything else not explicitly handled.

Using a for loop combined with the case statement means you don't have to care about the order the options are passed in.

In your example, to handle "--option1 --option2" you could do...



for i in $* ; do
case "$i" in
--option1 ) echo "Doing option1 stuff" ;;
--option2 ) echo "Doing option2 stuff" ;;
* ) echo "Hrmm, don't know $i option" ;;
esac
done



Hope that helps.
-weresheep

[slavik]

cute, but wrong.

look up getopt. :)

[ghostdog74]

getopts. Search the link on learning bash in my sig and you can find examples of using getopts.

[mssever]

getopts > getopt. The s makes all the difference.

[jesushero]

Hello,

Here is the method I use for program options for shell scripts...



for i in $* ; do
case "$i" in
-t ) RETAG=1 ;;
-m ) MP3=1 ;;
-r ) REVERSE="-r" ;;
. ) MUSICDIR=$(pwd) ;;
* ) MUSICDIR="$i" ;;
esac
done


The $* in the for loop expands to all the provided options.

The * ) in the switch (case) statement is like C's default case. It means anything else not explicitly handled.

Using a for loop combined with the case statement means you don't have to care about the order the options are passed in.

In your example, to handle "--option1 --option2" you could do...



for i in $* ; do
case "$i" in
--option1 ) echo "Doing option1 stuff" ;;
--option2 ) echo "Doing option2 stuff" ;;
* ) echo "Hrmm, don't know $i option" ;;
esac
done



Hope that helps.
-weresheep

Worked great, thanks! I hadn't thought of doing it this way (apparently). Actually, it worked better than getopt or getopts for what I wanted to do, it's more flexible. Do you want to be credited in the distributed version? If so, let me know how would you like your name/nickname to appear.

[jesushero]

cute, but wrong.

look up getopt. :)

Thanks, but getopt and getopts didn't work that well for what I was trying to do, they were too specific and I wanted to be able to include both short/long options and one non-option argument. The simple script above worked a treat. I implemented the non-option argument in there, instead of doing it separately as I would have to do with getopt/getopts.

Thanks anyway, I'll keep that in mind for future use, I'm sure it will come in handy.

[slavik]

Thanks, but getopt and getopts didn't work that well for what I was trying to do, they were too specific and I wanted to be able to include both short/long options and one non-option argument. The simple script above worked a treat. I implemented the non-option argument in there, instead of doing it separately as I would have to do with getopt/getopts.

Thanks anyway, I'll keep that in mind for future use, I'm sure it will come in handy.
getopt shifts the options out and you get left with your non-option argument (like a filename)

[weresheep]

Worked great, thanks! I hadn't thought of doing it this way (apparently). Actually, it worked better than getopt or getopts for what I wanted to do, it's more flexible.


I've had a quick look at the getopt man page but never heard of getopts before. I'm sure I'll get around to reading up on them at some point, but I find the loop works well for me.


Do you want to be credited in the distributed version? If so, let me know how would you like your name/nickname to appear.

Heh, thanks but thats okay. Just glad it helped.

-weresheep

[ghostdog74]

I've had a quick look at the getopt man page but never heard of getopts before. I'm sure I'll get around to reading up on them at some point, but I find the loop works well for me.



Heh, thanks but thats okay. Just glad it helped.

-weresheep

getopts is internal to bash. Its a bash builtin. As for the loop method, that's fine if you don't have option arguments. say if you have optio in -a and it takes in an argument, eg -a 10, then you can use OPTARG to get "10". in this case, its better to use getopts

[weresheep]

getopts is internal to bash. Its a bash builtin. As for the loop method, that's fine if you don't have option arguments. say if you have optio in -a and it takes in an argument, eg -a 10, then you can use OPTARG to get "10". in this case, its better to use getopts


Ah, thanks for explaining the use case for getopts, I'll do some reading up on it.

Thanks,
-weresheep