unset(3tcl)

📦 version 9.0.4, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu questing, ubuntu resolute, ubuntu stonking

💖 unset — the Tcl Built-In Commands glow-up 💖

okay bestie, pull up a chair, because this one is literally the little command that could. it's unset, it lives in the Tcl Built-In Commands family, and its whole job is making variables ✨ cease to exist ✨. no cap.

🌸 NAME 🌸

unset — delete variables. that's it. that's the gig. it's giving "girl, bye" but for your variable table. 💅

🎀 SYNOPSIS 🎀

unset ?-nocomplain? ?--? ?name name name ...?

look at those question marks, they're all optional, it's very low-pressure, very chill of it honestly 🦋

✨ DESCRIPTION ✨

so here's the tea: this command removes one or more variables. every name you hand it is a variable name, and you can write it any of the ways that the set command accepts. same energy, same syntax rules, it's just the deletion arc of the character development. 💜

if a name points to an element of an array, then just that one element gets removed — the rest of the array is totally fine, untouched, thriving, unbothered. 👑

but if a name is just an array name with no parenthesized index? oh she's taking the WHOLE array out. entire thing. gone. no survivors, no crumbs. 😭

the unset command returns an empty string as its result. iconic behaviour honestly, returns nothing and expects nothing, main character energy fr fr.

now, the options, bestie, listen up:

  • if -nocomplain is specified as the first argument, any possible errors get suppressed. the drama is cancelled. 🙈
  • that option may not be abbreviated — and this is on purpose! it's to disambiguate it from possible variable names. so no shortening it, no nicknames, it answers to its full government name only. 💀
  • the option -- indicates the end of the options, and you should use it if you want to remove a variable that has the same name as any of the options. it's the "okay we're done with flags, everything after this is a real name" separator. 🫶
⚠️ big important warning moment: if an error occurs during variable deletion, any variables after the named one that caused the error are not deleted. so it's not all-or-nothing, it's like... it got partway through the list and then tripped and dropped the rest of the tray. 🍓

an error can occur when:

  • the named variable does not exist, or
  • the name refers to an array element but the variable is actually a scalar, or
  • the name refers to a variable in a non-existent namespace.

so yeah, three little landmines, know them, respect them, or just yell -nocomplain at the top and vibe. 🌈

🔥 EXAMPLE 🔥

okay this example is SO cute, we're making an array that maps some numbers to their squares, and then we're deleting the non-prime ones like a little math bouncer at the club. 🎀

Create an array containing a mapping from some numbers to their squares and remove the array elements for non-prime numbers:

array set squares {
    1 1    6 36
    2 4    7 49
    3 9    8 64
    4 16   9 81
    5 25  10 100
}

puts "The squares are:"
parray squares

unset squares(1) squares(4) squares(6)
unset squares(8) squares(9) squares(10)

puts "The prime squares are:"
parray squares

see how it's unset squares(1) with the parens? that's the element form, so the array survives, just those specific little squares get evicted. 🧚 the array is still standing, still serving, just leaner and prime-er. ⭐

💫 SEE ALSO 💫

go read these next, they're the friend group:

👑 KEYWORDS 👑

remove, variable

and that's the whole page bestie!! written by the Tcl crew, version 8.4, and this manual page is unset(3tcl) — mwah, periodt. now go delete something responsibly. 💖✨🎀🦋🌸💅🫶

📦 where this page comes from