passing arg to function / alias

passing arg to function / alias

[TJ Luoma]

I am trying to figure out how to pass optional arguments to a shell
script and then have them be passed on to another program.

I'm not sure I can explain this well, so I'm going to try to
demonstrate what I mean with an example.

Imagine this is a program called 'list.zsh':

	#!/bin/zsh -f

	LS_ARG="-l"

	case "$@" in
		-j)
					LS_ARG="-t -r $LS_ARG"
					shift
		;;

		-z)
					LS_ARG="-R -t $LS_ARG"
					shift
		;;
	esac

	eval /bin/ls ${LS_ARG} $@

	exit 0

In this example, I want 'list.zsh' to ALWAYS do 'ls -l' but

* if I add '-j' I want it to do the equivalent of 'ls -l -t -r'
* if I add '-z' I want it to do 'ls -l -R -t'

Ideally, since /bin/ls has a lot of other flags, I would like to be
able to do this too:

./list.zsh -j -z -s /path/to/dir

and have "-s" just "passed along" to "/bin/ls" as another argument.

('list.zsh' is just for example purposes. I'm trying to figure out how
to do this same thing for several different programs, including curl
and lynx and others.)

I thought that if I looped through the arguments using 'case' and
appended each argument to the variable 'LS_ARG' then:

The results are pretty terrible.

list.zsh pretty much only works if I don't give it any arguments or if
I just give it one of -z or -j. If I give it two (as in "list.zsh -j
-z" or even "list.zsh -z -S"), 'ls' complains that j/z are illegal
arguments.

Is this even possible?

If so, what am I doing wrong?

Thanks for your time.

TjL

Re: passing arg to function / alias

[Bart Schaefer]

On Jul 17,  3:29pm, TJ Luoma wrote:
} Subject: passing arg to function / alias
}
} I thought that if I looped through the arguments using 'case' and
} appended each argument to the variable 'LS_ARG' then:
} 
} The results are pretty terrible.

"case" doesn't loop by itself, you need to call it inside one.  Also
in zsh you probably want to use an array rather word splitting.
Something like

    local -a LS_ARG
    while [[ $# -gt 0 && "$1" = -* ]]
    do case "$1" in
       -j) LS_ARG=(-t -r $LS_ARG);;
       -z) LS_ARG=(-R -t $LS_ARG);;
       *) LS_ARG=($LS_ARG $1);;
       esac
       shift
    done

    /bin/ls -l $LS_ARG $@

However, you might want to look at the "getopts" builtin if you want
to write this in a POSIX-portable way, or at the "zparseopts" builtin
for a zsh-specific alternative.

Re: passing arg to function / alias

[TJ Luoma]

On Sun, Jul 17, 2011 at 5:42 PM, Bart Schaefer
<schaefer@brasslantern.com> wrote:
>
> "case" doesn't loop by itself, you need to call it inside one.

Oops! I actually knew that but neglected it in my example

> Also
> in zsh you probably want to use an array rather word splitting.
> Something like
>
>    local -a LS_ARG
>    while [[ $# -gt 0 && "$1" = -* ]]
>    do case "$1" in
>       -j) LS_ARG=(-t -r $LS_ARG);;
>       -z) LS_ARG=(-R -t $LS_ARG);;
>       *) LS_ARG=($LS_ARG $1);;
>       esac
>       shift
>    done
>
>    /bin/ls -l $LS_ARG $@

AHA! An array worked perfectly for me. Thanks!

> However, you might want to look at the "getopts" builtin if you want
> to write this in a POSIX-portable way, or at the "zparseopts" builtin
> for a zsh-specific alternative.

I decided to go "all in" on zsh for my scripting, so I'm not worried
about "portability" (not that it's not a bad goal, just one that I've
chosen not to worry about given finite resources of time and attention
and memory, since these are for personal use.)

That said 'zparseopts' has gone into my list of "ZSH Things To Learn"
but for now, arrays for everyone!

Thanks!

TjL

ps - sorry for the reply-delay. I've only now had a chance to go in
and try this. Where did July go? How is the summer almost over
already!?