Man pages › Compared with Linux and the BSDs

`id(8)` on Solnix vs Linux and the BSDs

On Solnix, id is the illumos id at /usr/bin/id. Its -p adds a project ID (projid=) to the default line, whereas on the BSDs -p makes the output human-readable on separate lines. Its -a is a real option that adds all groups, whereas Linux and FreeBSD ignore it.

The manual pages

Solnix: id(8) from pkgs.solnix.illumos-world-man · illumos.org
Linux: id(1) coreutils-full-9.11
FreeBSD: id(1) 15.1-RELEASE
OpenBSD: id(1) 8.0
NetBSD: id(1) 11.0
Standard: POSIX.1-2024 (IEEE Std 1003.1-2024), id

What Solnix runs

A default Solnix system runs the illumos /usr/bin/id. /usr/xpg4/bin/id has the same synopsis. The page says that only /usr/xpg4/bin/id also writes supplementary group affiliations in the default output; the bundle does not describe /usr/bin/id doing so. The ATTRIBUTES table lists /usr/bin/id as Stable and /usr/xpg4/bin/id as Standard.

Differences

Compared with	Topic	What differs
FreeBSD, OpenBSD, NetBSD	`-p` meaning	On Solnix, id `-p` appends projid=%u(%s) to the normal one-line output. On FreeBSD, OpenBSD and NetBSD, `-p` switches to a human-readable multi-line output with the keywords login, uid, euid, rgid and groups. Source: Solnix id(8) -p; FreeBSD id(1) -p; OpenBSD id(1) -p; NetBSD id(1) -p
Linux	`-p` missing on Linux	Solnix has `-p` for project membership. The Linux id page documents no `-p` option, so a script using id `-p` fails or behaves differently there. Source: Solnix id(8) -p; Linux id(1) options list
Linux, FreeBSD	`-a` meaning	On Solnix, `-a` reports the user name, user ID and all groups, and is invalid with `-G`, `-g` or `-u`. Linux and FreeBSD ignore `-a` for compatibility. OpenBSD and NetBSD do not document `-a`. Source: Solnix id(8) -a, OPTIONS; Linux id(1) -a; FreeBSD id(1) -a; OpenBSD id(1) SYNOPSIS; NetBSD id(1) SYNOPSIS
all four	`-G` output format	Solnix `-G` prints each ID with the format %u, separated by a space, and ends with a newline. FreeBSD, OpenBSD and NetBSD say the IDs come as whitespace-separated numbers in no particular order. The Linux text does not describe the separator. Source: Solnix id(8) -G; FreeBSD id(1) -G; OpenBSD id(1) -G; NetBSD id(1) -G; Linux id(1) -G
Linux	multiple users and `-z`	Linux id accepts several USER operands and has `-z` to separate entries with NUL. The Solnix synopsis takes a single optional user and has no `-z`. Source: Linux id(1) SYNOPSIS, -z; Solnix id(8) SYNOPSIS, OPERANDS
all four	long options	Linux documents long options such as `--user`, `--group`, `--groups`, `--name` and `--real`. The Solnix page documents only single-letter options. Source: Linux id(1) -u, -g, -G, -n, -r; Solnix id(8) OPTIONS
Linux, FreeBSD, OpenBSD	extra options not on Solnix	Solnix has none of these: Linux `-Z` (security context), FreeBSD `-A`, `-M`, `-P`, `-c`, `-d` and `-s`, OpenBSD `-c` and `-R`. Scripts using them must not assume they exist on Solnix. Source: Linux id(1) -Z; FreeBSD id(1) SYNOPSIS; OpenBSD id(1) -c, -R; Solnix id(8) SYNOPSIS
FreeBSD, OpenBSD, NetBSD	default output when a name cannot be mapped	Solnix omits the (%s) name part when an ID cannot be mapped to a name. With `-n`, the BSDs display the number instead if an ID cannot be mapped. The Solnix page does not say what `-n` does in that case. Source: Solnix id(8) Formats, -n; FreeBSD id(1) -n; OpenBSD id(1) -n; NetBSD id(1) -n
FreeBSD, OpenBSD, NetBSD	user operand	The BSD pages say user may be a login name or a user ID. The Solnix page describes the operand only as a user (login) name. Source: Solnix id(8) OPERANDS; FreeBSD id(1) DESCRIPTION; OpenBSD id(1) DESCRIPTION; NetBSD id(1) DESCRIPTION
all four	exit status	Solnix, FreeBSD, OpenBSD and NetBSD document exit 0 on success and >0 on error. The Linux page excerpt documents no exit status. Source: Solnix id(8) EXIT STATUS; FreeBSD/OpenBSD/NetBSD id(1) EXIT STATUS; Linux id(1)

Standards

POSIX: id is a POSIX.1-2024 utility.
Solnix: Interface Stability: /usr/bin/id is Stable; /usr/xpg4/bin/id is Standard.
OpenBSD: The id utility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification. The flags [-cpR] are extensions to that specification.
NetBSD: The id function is expected to conform to IEEE Std 1003.2 (“POSIX.2”).
FreeBSD: The -A, -M, -P, -c, -d, -p, and -s options are FreeBSD extensions.

Writing portable scripts

Stick to -u, -g, -G, -n and -r, which every page documents. Avoid -p and -a, which differ between systems.
Do not rely on the order of IDs from id -G; the BSD pages say it is in no particular order.

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.