List all valid users under home directory

Question

I am on an AWS instance and have need to make a list of all the usernames on this instance. Something simple like:

ls /home > users.txt

would suffice, but I then need to go through each name and check its PID number, from there if the user doesn't have a PID number (ie a non zero return value) then I would like to delete it from the users text file i created.

I have tried the following, but received many errors:

#!/bin/bash

ls /home > users_inc.txt
while read line
do
    id -u $line
    if [$? -e 0]
    then
        echo $line > users.txt
    fi
done < users_inc.txt

Fairly new to bash scripting, any help would be appreciated.

Do you main UID (user ID) and not PID (process ID)? If you already know which UIDs you want to delete, why bother with this loop? — jordanm, Jan 27 '20 at 22:35

Léa Gris · Answer 1 · 2020-01-28T10:30:57.593

Alternate method using awk:

getent passwd|awk 'BEGIN{FS=":"}{if(match($6,"/home/"$1)&&$3>=1000)print$1}'

getent passwd: Stream accounts records database
awk 'awk script': Execute awk script to parse accounts records

The awk script:

BEGIN{
  FS=":"
}
{
  if (match($6, "/home/"$1) && $3>=1000)
    print $1
}

BEGIN{}: Awk Initialization block executed once for the whole input stream.
- FS=":": Define : as the Field Separator
{}: Main code block executed for each line or record of the input stream.
- if (match($6, "/home/"$1) && $3>=1000): If field #6 witch is the home directory path matches /home/username (field #1) && and field #3 UID >= greater-than or equals to 1000 (minimum UID for normal accounts)
- print $1: Then print the User Name from field #1.

That's a pretty darn clever solution. – David C. Rankin Jan 28 '20 at 04:13 — David C. Rankin, Jan 28 '20 at 04:13

codeforester · Answer 2 · 2020-01-27T22:48:40.143

2

Modified your script, fixing the issues:

cd /home || { printf '%s\n' "Can't cd to /home" >&2; exit 1; }
for user in *; do
    if id -u "$user" >/dev/null 2>&1; then
        printf '%s\n' "$user"
    fi
done > /path/to/users.txt

Assumed that you meant ID and not PID.

answered Jan 27 '20 at 22:42

codeforester

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thank you for your very detailed answer. i made some edits to my original code and was able to get that to work instead, it just fit better with what i am trying to do. – Jay Wehrman Jan 27 '20 at 23:45

List all valid users under home directory

2 Answers2