Shell Programming and Scripting

Code:

#! /usr/bin/sh

func () {

        echo " PRAMATER RECEIVED IS $1"
        return 1
}
VALUE=$(func "Hi")

Not Working!. but if i invoke like:

Code:

func "Hi"

Works!!

Wat is it that i missing in previous invocation and why it is not working ..

What do you mean by "Not working!"? Is it printing a diagnostic message? (If so, what is the message?)

What system are you using? On some systems, /usr/bin/sh may be a Bourne shell that doesn't recognize the $(...) form of command substitution. If that is the case, you could try:

Code:

VALUE=`func "Hi"`

Are you just saying that VALUE=$(func "Hi") didn't produce any output. If so, know that it shouldn't produce any output. If you wanted to see that the variable assignment worked as expected, you could use:

Code:

echo "$VALUE"

after the assignment to see what has been stored in the shell variable VALUE.

Not Working means function statements are not executed(no diagnostic msg either) so prompt is returned without any output.

i tried :

VALUE=`func "Hi'` did not work(above statement holds good here also)...

So, wat is it that i am missing here?

echo $VALUE yes i will add this line, but a question here can i get a string in VALUE from function? or can i return a string from function?

Both of the statements that you say are not working seem to be working just fine. Neither of them should produce any output. Both:

Code:

VALUE=`func "Hi"`

and

Code:

VALUE=$(func "Hi")

assign the text produced by func to the variable named VALUE (after stripping off the trailing newline). That assignment does not produce any output unless the shell detects an error while performing the assignment.

Note however, that the command:

Code:

VALUE=`func "Hi'`

is very different from the command:

Code:

VALUE=`func "Hi"`

because the opening quote and closing quote around Hi have to match.

yes, the execution is fine with no errors but at the same time no output(which is not wat is expected).

i am expecting the
echo "PRAMATER RECEIVED IS $1"
to get executed and is seen on STDOUT.

in any of the cases

VALUE=`func "hi"`
or
VALUE=$(func "hi")

Your expectation is wrong. That is not the way the shell works when you use command substitution in an assignment. The echo is executed, but it will not be seen on STDOUT because you are capturing the output and assigning it to a variable instead of writing it to STDOUT.

Based on what do you think this is not the expected output?

Adding to Don Cragun's explanation, from your example, when you run a command in backticks, the output of that command is stored in a variable.

When you say cont=`cat file.txt`, the contents of file.txt are stored in variable "cont".

Similarly, when you invoke the function "func", the output of func is stored in variable "VALUE". This is the expected behaviour.