How to use Internal Field Separator correctly?

Question

I am trying to set the IFS to ':', but it seems to not work. Here is my code,

FILE="/etc/passwd"

while IFS=':' read -r line; do
        set $line
        echo $1
done < $FILE

When I run my code, it seems to give me the entire line. I have used the set command to assign positional parameters, to extract only the username, but it output the entire line when I try to print the first positional argument $1. What am I doing wrong?

Answer 1

• IFS=':' read -r line reads the complete line
• IFS=':' read -r name remainder puts the first field in the variable name and the rest of the line in remainder
• IFS=':' read -r name password remainder puts the first field in the variable name, the second field in the variable password and the rest of the line in remainder.
• etc...

In bash you can use read -a array_var for getting an array containing all the fields, and that's probably the easiest solution for your purpose:

#!/bin/bash

while IFS=':' read -r -a fields
do
    echo "${fields[0]}"
done < /etc/passwd