Linux Shell Programming. Implementing a Search, Find and Replace Technique

[Tamara063]

I have to implement an application in shell programming (Unix/Linux).

I have to search a word from a text file and replace that word with my given word. I have a knowledge on shell and still learning.

I am not expecting source code. Can anybody help me or suggest me or give me some similar solution.

[salem c]

https://linux.die.net/man/1/sed
Eg

sed -i -e 's/haystack/needle/g' myfile.txt