Man pages › Compared with Linux and the BSDs

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

On a default Solnix system, alias and unalias exist as standalone utilities at /usr/bin/alias and /usr/bin/unalias, and the page also documents the csh, ksh and ksh93 built-ins, whose syntax differs. The FreeBSD and NetBSD pages in the bundle are shell built-in indexes or the csh page, not alias descriptions, so most comparison is against what those pages do not say.

The manual pages

Solnix: alias(1) from pkgs.solnix.illumos-world-man · illumos.org
FreeBSD: alias(1) 15.1-RELEASE
NetBSD: alias(1) 11.0
Standard: POSIX.1-2024 (IEEE Std 1003.1-2024), alias

What Solnix runs

A default Solnix system runs the illumos alias at /usr/bin/alias (and /usr/bin/unalias). /usr/xpg4/bin/alias is also shipped. The bundle does not say how it differs. The page also documents the csh, ksh and ksh93 built-in forms, which behave differently from /usr/bin/alias and from each other. No Linux counterpart page is in the bundle.

Differences

Compared with	Topic	What differs
FreeBSD	what the counterpart page is	The FreeBSD alias(1) page is the builtin(1) index of csh(1) and sh(1) built-ins. It has no description of alias options, operands or output. Solnix has a full alias/unalias page. Source: FreeBSD alias(1) NAME, DESCRIPTION; Solnix alias(1) DESCRIPTION, OPERANDS
NetBSD	what the counterpart page is	The NetBSD alias(1) page in the bundle is the csh(1) page. Its visible text does not mention alias or unalias, so the manual excerpt gives nothing to compare for alias syntax. Source: NetBSD alias(1) NAME, SYNOPSIS (csh)
FreeBSD	standalone utility vs script	Solnix lists `/usr/bin/alias` and `/usr/bin/unalias` as standalone commands. FreeBSD marks alias and unalias 'No': they exist externally, but only as scripts that use the shell builtin of the same name. Both are built into csh and sh. Source: FreeBSD alias(1) Commands table (alias, unalias) and 'No' note; Solnix alias(1) SYNOPSIS
FreeBSD, NetBSD	definition syntax by shell	On Solnix the syntax depends on the shell: csh is 'alias name def' (no '='), ksh and ksh93 are 'alias name=value', and `/usr/bin/alias` takes 'alias-name=string'. The FreeBSD page only says csh and sh provide alias, and the NetBSD excerpt is silent. Source: Solnix alias(1) SYNOPSIS (csh, ksh, ksh93); FreeBSD alias(1) Commands table
FreeBSD, NetBSD	options on alias	`/usr/bin/alias` takes no options. Solnix ksh alias accepts `-t` and `-x`, and ksh93 alias accepts `-p`, `-t` and `-x`. In ksh93, `-x` is ignored and `-t` is obsolete. The FreeBSD page documents no alias options and the NetBSD excerpt shows none. Source: Solnix alias(1) SYNOPSIS, OPTIONS (ksh, ksh93); FreeBSD alias(1) Commands table
FreeBSD, NetBSD	ksh93 `-p` output	Solnix ksh93 alias `-p` prints definitions as alias commands that can be fed back to the shell to recreate them. The FreeBSD and NetBSD pages in the bundle document no equivalent. Source: Solnix alias(1) OPTIONS ksh93 -p; FreeBSD alias(1); NetBSD alias(1)
FreeBSD, NetBSD	unalias forms	Solnix `/usr/bin/unalias` takes alias names or `-a`. Solnix csh unalias takes a filename-substitution pattern, so 'unalias *' removes all aliases. ksh93 unalias `-a` ignores any name operands. The BSD pages in the bundle do not describe unalias arguments. Source: Solnix alias(1) SYNOPSIS, DESCRIPTION (csh, ksh93), OPTIONS (unalias -a)
FreeBSD, NetBSD	alias scope and timing	On Solnix csh, an alias must have been entered on an earlier command line before it can be used. In ksh93, an alias only affects scripts read by the current shell environment, not scripts it runs. In ksh, exported aliases (`-x`) are defined for scripts invoked by name. Source: Solnix alias(1) DESCRIPTION csh, ksh93, ksh
FreeBSD, NetBSD	exit status	Solnix `/usr/bin/alias` exits >0 if an alias-name operand has no alias definition, or on error. Solnix ksh alias exits non-zero when a name is given without a value and no alias exists. The BSD pages in the bundle give no alias exit status. Source: Solnix alias(1) EXIT STATUS, DESCRIPTION ksh; FreeBSD alias(1); NetBSD alias(1)

Standards

POSIX: alias is a POSIX.1-2024 utility.
Solnix: Interface Stability: Committed (csh, ksh). Standard: see standards(7).

Writing portable scripts

In portable scripts, use only 'alias name=value' and 'unalias name', and do not rely on -p, -t or -x. They are ksh or ksh93 options, and the BSD pages in the bundle do not document them.
Do not use csh-style 'alias name def' in sh or ksh scripts. Solnix csh uses a space, while ksh, ksh93 and /usr/bin/alias use '='.

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.