Andreas
c9c8714651
procps-ng 4.0 rewrote w to skip utmp entirely, leaving TTY blank, IDLE identical for all users, and WHAT pointing at the sshd parent process instead of the user's shell. Reads utmp via who(1), idle via tty atime, and foreground process group via the tpgid field in /proc/pid/stat. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
57 lines
1.8 KiB
Markdown
57 lines
1.8 KiB
Markdown
# w
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Drop-in replacement for `w(1)` on systems with **procps-ng 4.x**.
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## Problem
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procps-ng 4.0 rewrote `w` to read from `/proc` instead of utmp, but
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the process→session→tty mapping is broken. On a typical SSH login you get:
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```
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USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
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andreas 192.168.10.11 12:52 2:17 0.00s ? sshd: andreas [priv]
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andreas 192.168.10.11 12:52 2:17 0.00s ? sshd: andreas [priv]
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```
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Three bugs in one:
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| Column | Bug | Root cause |
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|--------|-----|------------|
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| TTY | blank | utmp never read |
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| IDLE | same for everyone | can't stat the tty without knowing its name |
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| WHAT | shows `sshd: [priv]` | picks the SSH privilege-separation parent instead of the user's shell |
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## Solution
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This script reads the right sources directly:
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- **utmp** via `who -u` — correct TTY name, login time, source host
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- **`/dev/<tty>` atime** — real idle time
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- **`/proc/pid/stat` `tpgid` field** — kernel's own record of each tty's
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foreground process group, used for JCPU/PCPU/WHAT (no `TIOCGPGRP` ioctl
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needed, which would fail on terminals we don't own anyway)
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## Example output
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```
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13:07:07 up 15 min, 3 users, load average: 0.05, 0.10, 0.09
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USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
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andreas pts/0 192.168.10.11 12:52 1:54 0.0s 0.0s -bash
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andreas pts/1 192.168.10.11 12:52 0s 37.5s 37.5s claude
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stephan pts/2 192.168.10.165 13:02 1s 0.0s 0.0s -bash
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```
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## Install
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```sh
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cp w ~/bin/w
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chmod +x ~/bin/w
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```
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Make sure `~/bin` appears before `/usr/bin` in your `PATH`.
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## Requirements
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Python 3.6+, `who`, `uptime` — all standard on any Linux system.
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Tested on Ubuntu 24.04 (Noble) with procps-ng 4.0.4.
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