Shell Programming and Scripting

Hi All,

I need to execute some commands on each line of a file.
How do i iterate thru each line of a file?

In detail:

First i will have to go to the first line of the file and execute a series of commands on it and then take the second line of the file, execute a series of steps and so on. I need to repeat this process until the last line of the file.

Please help me.

Thanks in anticipation,
Ravi.

Welcome to the forums. The forum has a search feature which you can use to search for similiar posts that have come up before. See this post on the possible ways to parse a file - https://www.unix.com/tips-and-tutoria...se-a-file.html

I wouldn't recommend the script in that post for a number of reasons.

For a start, it will fail on filenames containing spaces or other pathological characters.

It uses non-standard syntax that will not work in many POSIX shells.

It does not correctly read the entire line in some of the functions.

It uses a command that is no longer found on most systems (line).

It is an overwhelmingly large script for a person who needs to ask this question, and there are no useful comments to the functions.


The correct answer to the question is "use a while loop", as in this example:

Code:

while IFS= read -r line
do
   printf "%s\n" "$line"
done < FILE

There are, of course, variations on this, and for a large file, it is probably better to use sed or awk, depending on what needs to be done with the file.