Shell Programming and Scripting

Hi.. am new to shell and trying to write the script for the below task. Intially new.txt will be empty.

Requirment is to update the version of deployment packages.First time CMD_HG-120-V1 should be updated in new.txt.
Next time when i run the script it should be CMD_HG-120-V2..Simiraly CMD_HG-120-V3...It should take latest version from new.txt file and increment the version in new.txt file.

This time it should be CMD_HG-120-V4 if the previous version is V3 in txt file.

CMD_HG-120-V1
CMD_HG-120-V2
CMD_HG-120-V3
....

Not clear.
What exactly is your request? Your script doesn't give the expected result? Gives error messages?
What's the contents of the txt file? Where is CMD_HG-120-V4-DEV-SUCCESS going to? Why do you define the myfile variable, but then use string constants for the target file? Why do you append to /tmp/file/new.txt/new.txt?

Hi Rudic,

I am new to shell and trying to write the script for the above task. Intially new.txt will be empty.

Requirment is to update the version of deployment packages.First time CMD_HG-120-V1 should be updated in new.txt.
Next time when i run the script it should be CMD_HG-120-V2..Simiraly CMD_HG-120-V3...It should take latest version from new.txt file and increment the version in new.txt file.

This time it should be CMD_HG-120-V4 if the previous version is V3 in txt file.

CMD_HG-120-V1
CMD_HG-120-V2
CMD_HG-120-V3
....

Seriously: DON'T edit post that others have referenced / answered, pulling the rug from under their feet, and wasting peoples' time who tried to analyze and understand what you posted.
Secondly: It is disappointing that you don't answer the questions asked concerning your post and the script therein. Do you expect people to code the script for you without any interaction of yours?

Very Sorry Rudic i thought my question is looking confusing so i edited to make it more clear.

Hmmm... howsoever, try

Code:

myfile="/tmp/file/new.txt"
num=$(tail -1 "$myfile" 2>/dev/null ||  echo CMD_HG-120-V0)
echo "${num%[[:digit:]]*}$((${num##*[[:alpha:]]} + 1))" >> "$myfile"

There is a huge difference between making a request more clear and removing the code about which you were asking questions. And, changing the requirements of your script after people have responded to your original question just confuses readers of your thread who are trying to help you and trying to make sense of the non-sensical responses to a post that no longer matches your original post.

If we go back to your original post (with CODE tags added, as captured in post #2 in this thread) and we assume that your file contains:

Code:

CMD_HG-120-V1
CMD_HG-120-V1-DEV-SUCCESS
CMD_HG-120-V2
CMD_HG-120-V2-DEV-SUCCESS
CMD_HG-120-V3

then what is assigned to the variable oldnum by the command:

Code:

oldnum=`cut -d '-' -f3 /tmp/file/new.txt

? Is that what you wanted?

What happens when you add 1 to a multi-line non-numeric string value using expr? Does it give you a number or does it print a diagnostic message instead?

If you're unwilling to answer these questions and the questions RudiC asked in post #2, this thread will be closed. We are here to help you learn how to fix your code to get the results you want. We are not here to act as your unpaid programming staff nor to try to guess at what you are trying to do.