UNSET(1P)

📦 version 2017a, in alpine 3.22, alpine 3.23, alpine 3.24, arch rolling, nixpkgs unstable, opensuse-leap 16.0

💅 UNSET(1P) — POSIX Programmer's Manual 🎀

okay bestie so this is UNSET(1P) from the POSIX Programmer's Manual, and it's literally the "never mind, forget I said that" button for your shell ✨

🌸 PROLOG 🌸

Real talk before we get into it: this manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ — so if you're on Linux, go consult the corresponding Linux manual page for the actual tea on Linux behavior. Or, plot twist, the interface might not even be implemented on Linux at all. 🙈 No cap.

✨ NAME ✨

unset — unset values and attributes of variables and functions

like… yeet a variable or a function out of existence. gone. not here anymore. 💨

🦋 SYNOPSIS 🦋

unset [-fv] name...

💖 DESCRIPTION 💖

Each variable or function specified by name shall be unset. periodt.

If -v is specified, name refers to a variable name, and the shell shall unset it and remove it from the environment. 🔥 Read-only variables cannot be unset. sorry babes, those are locked, the door does not open.

If -f is specified, name refers to a function, and the shell shall unset the function definition. bye bestie 👋

If neither -f nor -v is specified, name refers to a variable; and if a variable by that name does not exist, it is unspecified whether a function by that name, if any, shall be unset. (iykyk — that's a ✨do not rely on this✨ situation.)

Unsetting a variable or function that was not previously set shall not be considered an error, and it does not cause the shell to abort. so you can just swing wildly and nothing bad happens. slay. 🫶

The unset special built-in shall support the Base Definitions volume of POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines.

Also note that:

VARIABLE=

is not equivalent to an unset of VARIABLE — in that example, VARIABLE is set to "". she's empty but she's there, okay, that's different!! 😭 Also, the variables that can be unset should not be misinterpreted to include the special parameters (see Section 2.5.2, Special Parameters). those are built different.

💅 OPTIONS 💅

See the DESCRIPTION. (yes really, that's the whole vibe here — the options live up in the description, go look 💜)

🎀 OPERANDS 🎀

See the DESCRIPTION. (same energy, bestie)

⭐ STDIN ⭐

Not used. she doesn't want it.

🌈 INPUT FILES 🌈

None.

🧚 ENVIRONMENT VARIABLES 🧚

None.

💜 ASYNCHRONOUS EVENTS 💜

Default.

🍓 STDOUT 🍓

Not used. nothing to print, nothing to say.

🌸 STDERR 🌸

The standard error shall be used only for diagnostic messages.

✨ OUTPUT FILES ✨

None.

🦋 EXTENDED DESCRIPTION 🦋

None.

🔥 EXIT STATUS 🔥

  • 0 — All name operands were successfully unset. everything popped off, main character energy 👑
  • >0 — At least one name could not be unset. something held on 😭

💀 CONSEQUENCES OF ERRORS 💀

Default.

The following sections are informative. (so like, they're the bonus content, not the binding rules — cute but not contractual ✨)

🎀 APPLICATION USAGE 🎀

None.

💅 EXAMPLES 💅

Unset VISUAL variable:

unset -v VISUAL

Unset the functions foo and bar:

unset -f foo bar

look at that. two little commands. chef's kiss. 🧑🍳💋

🌈 RATIONALE 🌈

Consideration was given to omitting the -f option in favor of an unfunction utility, but the standard developers decided to retain historical practice. (they said no thank you, we're keeping the old ways 🙏)

The -v option was introduced because System V historically used one name space for both variables and functions. When unset is used without options, System V historically unset either a function or a variable, and there was no confusion about which one was intended. A portable POSIX application can use unset without an option to unset a variable, but not a function — the -f option must be used. so if you're being portable, use the flag. no vibes-based guessing, bestie. 💅

⭐ FUTURE DIRECTIONS ⭐

None.

🦋 SEE ALSO 🦋

  • Section 2.14, Special Built-In Utilities
  • The Base Definitions volume of POSIX.1‐2017, Section 12.2, Utility Syntax Guidelines

Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

Any typographical or formatting errors that appear in this page are most likely to have been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .

and that's the whole thing, bestie 🫶 this page came to you courtesy of IEEE/The Open Group, 2017 — so yeah, 2017 said "here's unset, go forth and unset things" and we are still obsessed. 💜✨ bye mwah 🎀

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