Shell Programming and Scripting

Ok, the second condition you should try was wrong, should be

Code:

if [ -z "$num" ]; then

EDIT: I changed the variable names to those from the last posts in the following text:
The script (bash script, you have to change /usr/local/bin/bash to what it is on your machine), and I changed the prompt text for "VAL" for better understanding.

Code:

$ cat tfs.sh
#! /usr/local/bin/bash

echo -e "Enter Serial Number: \c" ; read SNO
echo -e "Enter Value ($SNO): \c" ; read VAL
if [ -z "$VAL" ]; then
  VAL="$SNO"
fi
echo "SNO: $SNO, VAL: $VAL"

(My OS is FreeBSD and I have to use the flag "-e" to "expand" "\c").

I don't get it what you mean is not working, the output for me is:

Code:

_$ ./tfs.sh
Enter Serial Number: 12
Enter Value (12): 34
SNO: 12, VAL: 34
_$ ./tfs.sh
Enter Serial Number: 12
Enter Value (12):
SNO: 12, VAL: 12

If you only do <return> for "VAL" it should mean the default value from "SNO", in the last example "12". As I understand you this is what you want.
There is no possibility for you to edit the default value on the screen, the read command is reading from STDIN (which echoes to the screen), _not_ from the screen, so you can never reuse the printed default value from the screen, only reuse it in the script, like I (and others) described.

NB! this is how it works on FreeBSD as far as I know.

Yes, you are right...
Thanks for clarify and I tried too and its working fine.

Thanks.