Take input from read and place it a string in another file

Shell Programming and Scripting
1

Hi,
This is most likely a dumb question but I could not find answer to it elsewhere.

I'm building a simple menu with case /esac and want to read user's input:

Please enter XYZ ; read XYZ

How do I take the value of XYZ and insert it as a variable $XYZ in file file.txt ?

I may need to explain that I have existing variable IP="address" in file.txt and I need to substitute address with XYZ from the user's input

2

What else is in file.txt?

3

A long script

I have
IP="address" as a variable on the 4-th line

The point is to be able to take user's input for IP address and insert it into this file so it is a valid IP to be used throughout the script

4

Why insert it? Why not just use it? This is a strange-sounding system.

You could export it, and set it only in that script if it's not already set.

# outside the script
read IPADDRESS
export IPADDRESS
./myscript

#inside myscript, set the variable if nothing else did
[ -z "$IPADDRESS" ] && IPADDRESS="default.ip.address"

That way you don't need to hack apart your scripts with sed all the time, which sounds a recipe for disaster if I ever heard one...

5

You may be right. But how do I do that?

My Main Menu script is in one file that I execute first to define the values which are then inserted and the variable in the other file

What is the alternative?

6

I may have stealth-edited underneath you, see my example.

7 
${IPADDRESS:=ZZZ.XXX.YYY.AAA}

Will set the value of IPADDRESS to ZZZ.XXX.YYY.AAA if the variable had no value...

8

so that's what happens
I enter:

echo "Please enter a valid network adress (e.g 129.168.0.0/24)" ; read network;\
              if [ `echo "$network" | awk '{print length($0)}'` -eq 14 ] ;\
              then export $network ; ./script; \
              else echo "Wrong address - use slash notation / for subnet!"; fi

and the result is:

-sh: export: 192.168.0.0/24: bad variable name

????? Confused

---------- Post updated at 12:01 PM ---------- Previous update was at 11:59 AM ----------

OK I see I should have used the ` around the export command, but then it changes my whole script file ....

9 
 then export $network ; ./script; \

Is wrong!!!
You export the variable NOT its value...

 then export network ; ./script; \
10

Question:
Did you use the variable substitution as we have suggested? Where?