Question

I’m a bit stuck with a unix command.

I have a file called file.txt with the following content:

Customer1

name=Alice

pass=unix

dob=

Customer2

name=Destroyer

pass=windows

dob=

What I basically want is to use a unix command that would allow me to grep for the customer (i.e Customer1) then give its dob a value, say for example dob=1912

so the file.txt will become like

Customer1

name=Alice

pass=unix

dob=1912

I’ve been working with sed, here’s the command that I formulated:

sed “s/$(awk ‘c–>0;/Customer1/{c=3}’ file.txt | tail -1)/dob=1234/g” -i file.txt

This however will replace ALL occurrences of dob with dob=1234 (quite obvious).

Can someone give me a hint on how to lock on the specific dob for each customer and replace it?

Thanks in advance.

Answer 1

awk can do it by itself. see the one liner below:

 awk 'BEGIN{RS="dob=";OFS="\n\n"}$1~/Customer1/{$0=$0"dob=1234";print}' input

test : change customer1’s dob value to 7777:

kent$  cat t.txt
Customer1

name=Alice

pass=unix

dob=

Customer2

name=Destroyer

pass=windows

dob=

kent$  awk 'BEGIN{RS="dob=";OFS="\n\n"}$1~/Customer1/{$0=$0"dob=7777";print}' t.txt

Customer1

name=Alice

pass=unix

dob=7777

updated:

kent$  awk 'BEGIN{RS="dob=";OFS="\n\n"}$1~/Customer1/{$0=$0"dob=7777";print > "t.txt"}' t.txt

kent$  cat t.txt
Customer1

name=Alice

pass=unix

dob=7777

updated again

kent$  awk '/Customer1/{a++;}/dob=/&&a{$0="dob=7777";a=0;}1' t.txt > tmp.txt && mv tmp.txt t.txt

kent$  cat t.txt
Customer1

name=Alice

pass=unix

dob=7777

Customer2

name=Destroyer

pass=windows

dob=

updated with sed
actually, using sed (with convenient -i option) to handle this is also possible. I didn’t understand your requirement correctly, I thought you only want the specific Customer Block. so I picked awk. Now comes the sed version:

kent$  sed -ir '/Customer1/{x;s/.*/a/;x;} 
/dob=/{x;
        /a/{s/a//g; x;
                s/.*/dob=1234/; x;};
        x}' t.txt

kent$  cat t.txt
Customer1

name=Alice

pass=unix

dob=1234

Customer2

name=Destroyer

pass=windows

dob=