5

For me, uptime yields 9 users, but

ps -Af | cut -f1 -d' ' | sort | uniq | wc -l yields 14.

I'm not exactly sure where the 9 is coming from.

Before I jump to conclusions though, please let me know if you guys do not have such a discrepancy.

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  • You can use w to see more information about those 9 users. Your ps -Af pipeline does not work at all on any of my systems, but have you looked at what it's reporting without using wc -l? It is probably showing some UIDs that don't show up in uptime/w like noaccess, nobody, etc
    – jesse_b
    Aug 3, 2018 at 20:48
  • @Jesse_b I had no idea about w. Thank you. Yes, that is indeed what was happening. (On a side note, the -A means 'all', and -f means 'full'. Maybe try -e instead of -A? Idk what version of ps you are using, but mine is procps-ng ps(1)). A follow up: what is the difference between users that show up in w, and users like nobody, etc.?
    – extremeaxe5
    Aug 3, 2018 at 20:57

1 Answer 1

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4

You're comparing apples and oranges.

ps will list the processes running. You're then getting the count of unique process-owning user ids.

uptime will report the users logged on. By using utmp. More details at https://github.com/coreutils/coreutils/blob/master/src/uptime.c#L177

So, comparison of output, highlighting this, below.

# uptime
 16:52:37 up 30 days, 23:32,  1 user,  load average: 0.04, 0.04, 0.05
# w
 16:57:33 up 30 days, 23:37,  1 user,  load average: 0.00, 0.01, 0.05
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
steve    pts/0    cpc79909-stkp12- 16:50    5.00s  0.07s  0.28s sshd: steve [priv]
#


# ps -Af | cut -f1 -d' ' | sort | uniq | wc -l
7
# ps -Af | cut -f1 -d' ' | sort | uniq
chrony
dbus
polkitd
postfix
root
steve
UID
#
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4
  • 1
    What is the difference between a "user logged on" and a "process-owning user id?" Is there a distinction between a "logged on user" and a special one, like the superuser? I thought that all users essentially were on equal footing.
    – extremeaxe5
    Aug 3, 2018 at 21:00
  • So in the example, we've got a process running as username 'postfix'. That's some process relating to email. 'postfix' is a username. But it's not a user. Hope this helps.
    – steve
    Aug 3, 2018 at 21:12
  • 1
    it’s not? It is listed in /etc/passwd
    – extremeaxe5
    Aug 3, 2018 at 21:13
  • 1
    It's a username. But it's not someone who has logged onto the device. Folk logging onto the device is what 'uptime' reports. It doesn't report active processes by username.
    – steve
    Aug 3, 2018 at 21:15

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