Ubuntu findstr: command not found

`findstr` is a command used in Windows, and is not available in Ubuntu by default. In Ubuntu, you can use the `grep` command to search for strings in files.

For example, to search for the string "hello" in a file called "example.txt", you can use the following command:

grep "hello" example.txt

If you want to search for the string in multiple files, you can use the following command:

grep "hello" *.txt

This will search for the string "hello" in all the files with the extension ".txt" in the current directory.