Write script to create multiple users with pre-defined passwords

You have to supply the password on stdin. Replace:

passwd $iuser

with:

passwd "$iuser" <<<"$ipasswd$ipasswd"

or, as suggested by mklement0:

passwd "$iuser" <<<"$ipasswd"$'\n'"$ipasswd"

The incantation <<< creates a here-string. The string that follows the <<< is provided as standard in to the command which precedes the <<<. In this case we provide the two copies of the password that the passwd command wants.

(The script reads these passwords from a plain text file. I will assume that your situation is some special case for which this is not as dangerous as it normally would be.)

John1024's answer is the correct one - his warning about reading passwords from plain-text files bears repeating.

Let me show the solution in context, without the file-descriptor acrobatics (exec 3<, ...):

#!/bin/bash# NOTE: Be sure to run this script with `sudo`.# Read user and passwordwhile read iuser ipasswd; do  # Just print this for debugging.  printf "\tCreating user: %s with password: %s\n" $iuser $ipasswd  # Create the user with adduser (you can add whichever option you like).  useradd -m -s /bin/false $iuser  # Assign the password to the user.  # Password is passed via stdin, *twice* (for confirmation).  passwd $iuser <<< "$ipasswd"$'\n'"$ipasswd"done < <(paste users.txt passwords.txt)

• paste users.txt passwords.txt reads corresponding lines from the two files and puts them on a single line, separated with \t.
• The result is piped to stdin via a process substitution (<(...)).
• This allows read to read from a single source.
• $\n is an ANSI C-quoted string that produces a (literal) newline.

   #! /bin/bash   for i in {1..100}    do      `sudo mkdir -p /root/Desktop/userm$i`      `sudo useradd -m -d /root/Desktop/userm$i -s /bin/bash userm$i`       echo "userm$i:userm$i" | chpasswd   done

this will create 100 users.
user name will be (userm1-userm100).
home directory will be /root/Desktop/(userm1-user100)
password will be (userm1-userm100)