Very Computer

Hello

I have problem using alias inside autoloaded function,
it can be illustrated with the following example:

there is function definition file ./foo

function foo {
    msg

Quote:}

... and the main script ./main

#!/bin/ksh
alias msg='print Hello!'
FPATH=.
autoload foo
foo

when executing main script, there is error:
./main: foo[2]: msg: not found [No such file or directory]

what's wrong with this example?

It does't work under AT&T ksh (linux.i386 binary),
but works fine when use pdksh

blazk

Write a function instead of using an alias...

   function msg
   {
     print "Hello!"
   }

In a very limited context alias is fine for interactive shell use;
for scripting it makes more problems (more or less subtle) than is
of help, and it is not really necessary to use it here.

Quote:

> when executing main script, there is error:
> ./main: foo[2]: msg: not found [No such file or directory]

> what's wrong with this example?

> It does't work under AT&T ksh (linux.i386 binary),
> but works fine when use pdksh

Alias behaviour has changed from ksh88 to ksh93 (pdksh was -partly-
based on ksh88 functionality); for example, in ksh93 it is not
possible any more to export aliases to external scripts. I have no
ksh88 at hand so I cannot tell whether the behaviour you expect was
present in ksh88.

Janis

Quote:> blazk

Quote:> In a very limited context alias is fine for interactive shell use;
> for scripting it makes more problems (more or less subtle) than is
> of help, and it is not really necessary to use it here.

I'm writing a function for reporting errors, it prints error message
and i would like to print also the name of the calling script/function
and line number where the error occured.

i hoped it would be possible to wrap an actual error reporting function
with an alias that additionally passes ${0##*/} and $LINENO  to this
actual function

is it possible to do it in a similar way but without using alias?

blaz

If I understand correct you want it for "cosmetical" reasons, to avoid
passing ${0##*/} and $LINENO explicitly as arguments to the function.
You could do a preprocessing that instruments your scripts with that
additional code. (Similar solutions in the C language also use the cpp
preprocessor for such tasks.)

I haven't the book at hand but I think that Rosenblatt used some method
for passing line numbers in his shell de* example; you might want
to have a look at it. But AFAIR he also uses some form of preprocessing.

Janis

Works in Solaris 9 ksh88 but not ksh93.

Quote:> Alias behaviour has changed from ksh88 to ksh93 (pdksh was -partly-
> based on ksh88 functionality); for example, in ksh93 it is not
> possible any more to export aliases to external scripts. I have no
> ksh88 at hand so I cannot tell whether the behaviour you expect was
> present in ksh88.

seems that in ksh93 it is impossible to use aliases inside
autoloaded functions at all (except aliases that are compiled into the
shell, for example 'autoload' works:)

Source code of the function loader  src/cmd/ksh93/sh/path.c: funload()
suggests that alias expanding is explicitly turned off when function is
read
("sh_onstate(SH_NOALIAS)" line). I wonder why such restriction was
made...

on the other hand, ksh93 manual says:
"...Shell functions are read in and stored internally.
Alias names are resolved when the function is read...."
http://www.cs.princeton.edu/~jlk/kornshell/doc/man93.html#Aliasing
this is strange...

blaz

Quote:

> If I understand correct you want it for "cosmetical" reasons, to avoid
> passing ${0##*/} and $LINENO explicitly as arguments to the function.

yes, exactly
this is funny - the same solution is used in ksh93 source test scripts,
for example
'err_exit' function and corresponding 'err_exit' alias in
src/cmd/ksh93/tests/alias.sh
(but autoloaded functions are not involved, so it works...)

blaz