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How to reuse values in Shell script

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# 1  
Old 09-18-2012
How to reuse values in Shell script
Hi

I am trying to write a shell script and wanted to re-use the value which I have entered already.

Here is the sample code.
Code:
echo "Enter Value : \c" ; read val
echo  "Enter number: $val\c" ; read num

Now I wanted to change the value as showing in 2nd Line or if I will use enter, it should accept as it is.

Thanks in advance.
Last edited by Franklin52; 09-18-2012 at 05:32 AM.. Reason: Please use code tags for data and code samples
# 2  
Old 09-18-2012
This depends heavily on the shell and its version that you are using. In newer versions of bash, for instance, and if the readline packet is installed/used, you can use the -i option to put your variable into the line editing buffer to edit or accept it.
Another way would be to use a third variable to read into, compare to e.g. empty string and, if empty, leave the original value as is, otherwise overwrite it with the new value.
# 3  
Old 09-18-2012
Thanks for your prompt reply.

I am using AIX 6.1 and found that there is no option is working with read (either read -p or read -i).
Is there any other way I could accept the already entered value or enter new value.

Thanks.
# 4  
Old 09-18-2012
Again, this depends on your shell, which you do not mention. Try the second suggestion, sth. like
Code:
read tmp
if [ "$tmp""X" != "X" ]; then val=$tmp; fi

You may be able to use primaries like -n or -z in the test section.
Last edited by RudiC; 09-18-2012 at 10:02 AM..
# 5  
Old 09-18-2012
I am using bash. Also value should not be fix, it will always change.
Code:
echo "Enter Value : \c" ; read val
echo  "Enter number: $val\c" ; read num
if [ "$val""X" != "X" ]; then val=$num; fi

Output is
Code:
Enter Value : 12
Enter number: 1200

I am not able to remove value (12) from 2nd argument (When I am entering Number), so I just enter 00.

---------- Post updated at 01:53 PM ---------- Previous update was at 01:45 PM ----------

Code:
echo "Enter Value : \c" ; read tmp
echo  "Enter number: $val\c" ; read num
if [ "$tmp""X" != "X" ]; then val=$tmp; fi
echo $tmp
echo $num

Output is

Code:
Enter Value : 12
Enter number: 34    [ Here I entered the value as it was not appeard]
12
34

Enter Value : 12
Enter number:   [ Here I just press enter, but the value set to null].
12

Last edited by Franklin52; 09-18-2012 at 05:33 AM.. Reason: Please use code tags for data and code samples
# 6  
Old 09-18-2012
I don't unserstand. In your post #1 you "wanted to re-use the value" which means "don't overwrite/remove". So why do you want to remove it in post #5? This:
Code:
echo "Enter Value : \c" ; read val
echo "Enter number: $val\c" ; read num
if [ "$num""X" != "X" ]; then val=$num; fi
echo val: "$val", num: "$num"

does exactly what you requested: pressing <enter> on the second read retains the value read in first read, and entering a number assigns this number to variable val.
btw, you need to switch on echo's escape interpretation with the -e option.

---------- Post updated at 10:40 AM ---------- Previous update was at 10:37 AM ----------

Quote:
Originally Posted by SushilAnand
---------- Post updated at 01:53 PM ---------- Previous update was at 01:45 PM ----------

Code:
echo "Enter Value : \c" ; read tmp
echo  "Enter number: $val\c" ; read num
if [ "$tmp""X" != "X" ]; then val=$tmp; fi
echo $tmp
echo $num

Output is

Code:
Enter Value : 12
Enter number: 34    [ Here I entered the value as it was not appeard]
12
34

Enter Value : 12
Enter number:   [ Here I just press enter, but the value set to null].
12

Of course the value is null, as it was null before! You have to assign sth. to num that you want to keep. And you need to decide which variable you want to keep: val or num. This is not clear from your text and code.
# 7  
Old 09-18-2012
I want to keep both the value or may be want to use 1st entered value. Thanks.
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