Man pages › Compared with Linux and the BSDs

`who(1)` on Solnix vs Linux and the BSDs

On Solnix, who is the illumos who at /usr/bin/who, and it reads /var/adm/utmpx by default. It accepts far more flags than FreeBSD or OpenBSD (-a, -b, -d, -l, -p, -r, -t) and has -n, which no counterpart documents. -T is the flag most likely to surprise you, because its output differs between /usr/bin/who and /usr/xpg4/bin/who.

The manual pages

Solnix: who(1) from pkgs.solnix.illumos-world-man · illumos.org
Linux: who(1) coreutils-full-9.11
FreeBSD: who(1) 15.1-RELEASE
OpenBSD: who(1) 8.0
NetBSD: who(1) 11.0
Standard: POSIX.1-2024 (IEEE Std 1003.1-2024), who

What Solnix runs

A default Solnix system runs the illumos /usr/bin/who. /usr/xpg4/bin/who is also shipped. The page documents these differences: /usr/bin/who -T also writes idle, pid and comment, while the xpg4 -T writes only the state field. -s appears in the xpg4 synopsis only as the separate form 'who -s [-bdHlmpqrtu]'.

Differences

Compared with	Topic	What differs
all four	default database file	Solnix who reads `/var/adm/utmpx.` Linux and OpenBSD read `/var/run/utmp`, FreeBSD reads `/var/run/utx.active`, and NetBSD reads `/var/run/utmpx.` Solnix suggests `/var/adm/wtmpx` as the history file. Linux and OpenBSD suggest `/var/log/wtmp`, FreeBSD `/var/log/utx.log`, and NetBSD `/var/log/wtmpx` or `/var/log/wtmp.` Source: Solnix who(1) DESCRIPTION; Linux who(1) FILE text; FreeBSD who(1) DESCRIPTION; OpenBSD who(1) file; NetBSD who(1) file
all four	`-T` output	Solnix `/usr/bin/who` `-T` acts like `-s` but also writes state, idle, pid and comment. The xpg4 version writes only state. Linux and FreeBSD add a message-status character. OpenBSD and NetBSD print a character after the user name. Source: Solnix who(1) -T under /usr/bin/who and /usr/xpg4/bin/who; Linux who(1) -T; FreeBSD who(1) -T; OpenBSD who(1) -T; NetBSD who(1) -T
Linux	`-w` and long options	Solnix who has no `-w` and no long options. Linux accepts `-w`, `--mesg`, `--message` and `--writable` as synonyms for `-T`, plus `--all`, `--boot`, `--count`, `--heading` and others, as well as `--lookup`. A Linux script using these fails on Solnix. Source: Linux who(1) -T, -w, --mesg, --message, --writable, --lookup; Solnix who(1) SYNOPSIS
FreeBSD, OpenBSD	missing flags	FreeBSD who has no `-d`, `-l`, `-p`, `-r` or `-t`, and OpenBSD has no `-a` or `-b` either. Solnix has all of these. OpenBSD says `-abdlprst` are not supported by its who. Source: FreeBSD who(1) SYNOPSIS; OpenBSD who(1) SYNOPSIS, STANDARDS; Solnix who(1) SYNOPSIS
all four	`-n` users per line	Solnix who `-q` `-n` x sets the number of users shown per line, with x at least 1. `-n` works only with `-q`. None of the counterpart pages documents `-n`. Source: Solnix who(1) -n, SYNOPSIS; Linux, FreeBSD, OpenBSD, NetBSD who(1) SYNOPSIS
Linux, FreeBSD, NetBSD	`-a` contents	Solnix `-a` turns on `-b`, `-d`, `-l`, `-p`, `-r`, `-t`, `-T` and `-u`. Linux `-a` is the same set. FreeBSD `-a` equals `-bTu`. NetBSD `-a` equals `-bdlprTtuv`. OpenBSD has no `-a`. Source: Solnix who(1) -a; Linux who(1) -a; FreeBSD who(1) -a; NetBSD who(1) -a; OpenBSD who(1) SYNOPSIS
NetBSD	`-v` and `-r` detail	NetBSD has `-v`, which adds termination signals, exit status, session id and entry type. Solnix has no `-v`. Solnix `-r` only indicates the current run-level, whereas NetBSD `-r` documents its run-level letters (d, s, r, t, m, T, c). Source: NetBSD who(1) -v, -r; Solnix who(1) -r, SYNOPSIS
Linux, OpenBSD	am i operand	Solnix 'am i' and 'am I' are equivalent to `-m` only in the C locale, and the words must be separate arguments. Linux presumes `-m` for any two arguments ('mom likes' works). OpenBSD says 'am i' returns the invoker's real user name. Source: Solnix who(1) OPERANDS; Linux who(1) ARG1 ARG2; OpenBSD who(1) am i
Linux, OpenBSD, NetBSD	environment variables	Solnix lists LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, LC_TIME and NLSPATH. FreeBSD lists COLUMNS, LANG, LC_ALL and LC_TIME. The Linux, OpenBSD and NetBSD pages in the bundle document no environment variables. Source: Solnix who(1) ENVIRONMENT VARIABLES; FreeBSD who(1) ENVIRONMENT; Linux, OpenBSD, NetBSD who(1)
all four	single-user state	On Solnix, after shutdown to single-user state, plain who returns only a prompt, because utmpx is updated at login. who am i still reports correctly. No counterpart page mentions this. Source: Solnix who(1) NOTES; Linux, FreeBSD, OpenBSD, NetBSD who(1)
all four	init-related fields	Solnix `-d` adds an exit field for dead processes, and `-l` shows lines waiting for login with the name LOGIN. The comment field comes from `/etc/inittab.` The Solnix page documents this for init-based systems. Source: Solnix who(1) -d, -l, -p, DESCRIPTION; Linux who(1) -d, -l, -p

Standards

POSIX: who is a POSIX.1-2024 utility.
Solnix: ATTRIBUTES for /usr/xpg4/bin/who: Interface Stability is Standard.
FreeBSD: The who utility conforms to IEEE Std 1003.1-2001 (“POSIX.1”).
OpenBSD: Compliant with IEEE Std 1003.1-2008 (“POSIX.1”). Flags [-abdHlpqrst] are an X/Open System Interfaces option, and of these [-abdlprst] are not supported.
NetBSD: Expected to conform to IEEE Std 1003.2-1992 (“POSIX.2”).

Writing portable scripts

Portable scripts should use only -H, -m, -q, -T, -u and 'am i'. Every system in the bundle documents these, except that Solnix -T output and OpenBSD 'am i' behaviour differ.
Do not rely on -a, -n or -w. They mean different things or are missing across Solnix, FreeBSD, OpenBSD, NetBSD and Linux.
Do not hard-code the utmp path. Run plain who, or pass a file only after checking which of the paths above exists.

Every difference here is taken from the manual pages linked above: Solnix's published page, Linux (man-pages and the GNU and util-linux manuals), FreeBSD, OpenBSD and NetBSD. Each row names its source. Where a manual is silent, this page is too. Compiled 2026-10-26. Found a mistake? Mail hackers@lists.solnix.io.