topic Re: using "procedures" into shell scripts in Operating System - HP-UX

using "procedures" into shell scripts

Mauro Gatti — Mon, 28 Oct 2002 16:53:03 GMT

I know it is possible to use procedures in posix shell scripts like:

procname () {

command1
command1
...
}
recalled by "procname" into a script

but can I pass any value to these procedures?
like:

procname (arg1, arg2)
{
....
}

If I try I get a syntax error message.

Thank You

Re: using "procedures" into shell scripts

Stefan Farrelly — Mon, 28 Oct 2002 16:54:55 GMT

Yes, you can pass arguments to functions in posix shell - see man sh-posix (there is a whole section on functions near the bottom and arguments to them).

Basically the functions is defined as;
function ()

and when you call it later you pass arguments like you would a script;

A B C
which are passed to the function as $1 $2 $3 and so on.

Re: using "procedures" into shell scripts

Todd Lehr — Mon, 28 Oct 2002 16:55:54 GMT

The parameters will be passed as arguements into the procedure just like the main script, they become localized to the procedure. You also don't need to specify the params on the procedure line

proc()
{
echo "${1} is the first param"
}

proc Test

Also, the shift command will work just like it does in the main part of the script/

Todd Lehr

Re: using "procedures" into shell scripts

A. Clay Stephenson — Mon, 28 Oct 2002 17:02:08 GMT

Rather than procedures you have functions which can be denoted by the keyword 'function' or by simply following an identifier with () BUT there are no formal parameters. The actual parameters are simply positional variables $1,$2,$3 ... that are specific to the function.

e.g.

my_function()
{
echo "This is 1 ${1}"
shift
echo "This is 2 ${2}"
return 0
}

my_function("One",Two")

would result in
"This is 1 One"
"This is 2 Two"

Re: using "procedures" into shell scripts

A. Clay Stephenson — Mon, 28 Oct 2002 17:13:19 GMT

Ooops, I'm an idiot.

In the actual invocation of the function thare are no ()'s.

my_function("One",Two")

should be simply
my_function "One" "Two"

I've got to learn to read over my answers before hitting 'Submit'.

By the way, you can also capture the output of a function as well:

my_result=$(my_funct2 345)
stat=${?}

In this case ${my_result} would contain the stdout
of the function my_funct2 while ${stat} would contain the numerical result set by the 'return' in myfunct2.

Re: using "procedures" into shell scripts

Darrell Allen — Mon, 28 Oct 2002 19:16:23 GMT

Variables are also shared(usually) between functions and the calling program. Example:

#!/usr/bin/sh
#
# Functions
#
showit() {
echo $VAR
}

VAR="some value"
showit

VAR="some other value"
showit

man sh-posix for more info, particularly the "Functions" section.

Darrell

Re: using "procedures" into shell scripts

James R. Ferguson — Mon, 28 Oct 2002 20:11:49 GMT

Hi:

You can kludge the passing of parameters by value by using 'typeset' declarations within the scope of the shell function. A side benefit is inline self-documentation of the arguments passed. Try running this:

#!/usr/bin/sh
#
function me
{
X=${1}.updated
echo "fct_me : X=${X}"
}
function me2
{
typeset X=$1
X=${X}.updated
echo "fct_me2: X=${X}"
}
#
X=ORIGINAL.VALUE
me $X
echo "global : X=${X}"
#
X=ORIGINAL.VALUE
me2 $X
echo "global : X=${X}"
#
exit 0

Regards!

...JRF...