Prevent echo as a return value?

zizou86 · 01-25-2010, 10:24 AM

Hi,

I have always encountered this problem in ubuntu bash shell scripts that echo command in a function will be treated as a return value when used in a function.

e.g.

Code:

function abc
{
   echo "xyz"
}

returnVal=$(abc)
echo "Return value = $returnVal"

This would give the output

Return value = xyz

However, if I used:

Code:

function abc
{
   echo "xyz"
}

abc

The output would simply be xyz.

Hence the echo seems to function as a "return" command when used in a function with a return value.

Any workaround to this?

catkin · 01-25-2010, 10:41 AM

echo writes to stdout. In the first case the var=$(<function that runs echo) has the effect of capturing the stdout and assigning it to $var. In the second case stdout is not captured so appears on screen.

These are not return values; return values are set by bash' return command and accessed by the special variable "$?" (without the quotes).

zizou86 · 01-25-2010, 10:57 AM

Hi,

My apologies for the wrong usage of terms. Is there any way that I can prevent the echo in the function from being assigned to a variable other? I would like the echo to echo to stdout and nowhere else.

Thank you.

Regards.

catkin · 01-25-2010, 11:48 AM

Quote:

Originally Posted by zizou86

Is there any way that I can prevent the echo in the function from being assigned to a variable other? I would like the echo to echo to stdout and nowhere else.

Doesn't your second example do exactly that?

If you want some stuff echoed in the function to end up in a variable and some to end up going to the terminal you can redirect the terminal echoes to /dev/tty. Example (not using a function but illustrates the technique):

Code:

c:~$ var=$(echo foo; echo bar > /dev/tty)
bar
c:~$ echo $var
foo

zizou86 · 01-25-2010, 12:00 PM

Great thanks alot catkin. It worked great.

What I wanted was more to prevent the echo from going to the variable then anything.

Thanks a great deal.