Re: Shell script function problems

[Ken Irving <fnkci@uaf.edu>]

On Sat, Feb 09, 2008 at 12:36:53PM +0000, William Pursell wrote:
> phillinux wrote:
>>
>> I'm trying to write a bash shell script to create user accounts that  
>> calls 2 functions. I can't call these functions from the script or the  
>> command line. The set command seems to show the loaded script in the  
>> shell (loaded with . FunctionName at command line) with other  
>> environmental variables. ALSO: The type command does not recognize the  
>> function.
>>
>> The script and functions work on my laptop running Fedora (with one  
>> small glitch). Is there something I can do to my Debian server to get  
>> functions recognized??
>
> From some other comments in the thread, it sounds like you are trying
> to do something like the following:
>
>> $ cat foo
>>
>> g()
>> {
>>         printf 'in g\n'
>> }
>> $ cat bar
>> #!/bin/sh
>>
>> g
>> $ . foo
>> $ ./bar # won't work since bar doesn't source foo
>> ./bar: line 3: g: command not found
> ...
> If you source the file with the function definitions, it makes
> the functions available in the current shell, but not in subshells
> that you may invoke.

A qick perusal of bash(1) shows that functions can be exported to
subshells, e.g.:

    $ . foo
    $ ./bar
    ./bar: line 2: g: command not found
    $  export -f g
    $ ./bar
    in g

I suppose that could be (mis)used to implement some form of polymorphism
in shell scripts; the script executes g, but has no control over what g
actually is. Could be useful/confusing/dangerous...

I guess the same applies to sourcing function definitions from within
a script, since the function is still external to the script, though
it's at least defined in a file.

Ken

-- 
Ken Irving, fnkci+debianuser@uaf.edu