While talking about commands for command-line interface, I sometimes need to pronounce how command should be typed, like this one:

nc -l -p 1234

I used to pronounce - sign in this context as a "hyphen", or "dash", or probably "minus". But recently I got the video in which woman pronounces it like "tak" (starting from 3:00). I tried to explore the dictionary for words like "tack", "tuck", etc, but still can't find anything what would mean the - sign.

So, what is this word? And, what variants of pronunciation would be actually correct in this context?


Great question!

(A coincidence of https://english.stackexchange.com/a/190692/8286 )

Just FWIW, I say "minus" like you ("l s minus a l") or often just don't say the minus. So, in the example I'd read "n c l p 1234"

IMO very few people say hyphen. I'd say "dash" is common, but I'd say "minus" is more common than "dash".

Purely in my opinion: what she is saying (a) sounds silly and (b) I've never heard it before.

(Indeed, since 'tac' is a common command, it's doubly silly - but that's just me.)

Maybe someone here has heard it before?

Explained! - Military usage

Ahh! A user below has explained that "tac" is in fact military talk for the minus sign or hyphen.

All explained!

Again FYI I have never, ever, ever hear this in a computing / shell context.

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  • Thanks for the answer! Strangely enough, someone silently downvoted it.. – Dmitry Frank Aug 17 '14 at 20:18
  • cheers, no worries there votes mean almost nothing on this site! – Fattie Aug 18 '14 at 6:01

I'm the woman from the video. Saying 'tac' isn't silly at all. I grew up in a military family, so this was used regularly when speaking of a dash. Without getting into details, my father was in many fields where he was required to spell out commands via a speaking system, and they used tac. In school, we used 'dash'. Generally, I use tac when referring to commands as it is slightly quicker and easier to distinguish than saying hyphen or dash. I've never used the term 'minus sign' for a dash or a tac unless it's for a mathematical equation. I hope that answers your question.

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    Huh. Just came here after seeing your video. I have never heard "tac" to mean the terminal - character. – Brandon Arnold Apr 23 '16 at 2:56
  • People thought I was weird too. I find myself using dash when the character separates words (composer dump-autoload, dump dash autoload) and tac when it's the flag or separating distinct portions. – ToothlessRebel Dec 14 '17 at 22:28
  • Apologies for adding to the necro, but I'm simply shocked that so few people claim to be familiar with this usage... I guess I do come from parts of the US with a high level of Navy influence, but over a decade through various jobs and (non-military) postings at customer sites across the world, I've found that nearly every "technical" person (i.e. comfortable with a nix terminal) understood "rm tack rf" or "ls tack la" and the majority of them used it without hesitation. I guess mileage really does vary... anyway you and @ToothlessRebel are not completely insane. – A C Dec 22 '17 at 3:41
  • My first exposure to "tac option(s)" was also when I watched Hak5 for the first time (Awesome show by the way!). I really like the use of "tac" because "hyphen option(s)" is too much of a mouth full, and although there is an "en dash" which is technically a "dash" just slightly wider than a hyphen, it's generally interpreted by the eye as a hyphen. When I think of a dash, my mind usually thinks of the "em dash" (denoted by two hyphens "--" or a "—". Also, saying "tac" adds logical sense in that you are "tacking on" an option to the command. – Buggy Jul 4 '18 at 22:59
  • thanks @Shannon for explaining where it came from! – Fattie Mar 7 '19 at 17:04

According to a reddit.com post, this usage “originates as a navy term for flag signalling”:

A tackline is a length of halyard approximately 6 feet long; the exact length depends upon the size of flags in use. The tackline is transmitted and spoken as tack and is written as a dash (hyphen) "-". It is used to avoid ambiguity. It separates signals or groups of numerals that, if not separated, could convey a different meaning from that intended.

Other comments in the post say that tack is used in Air Force radio communications, for brevity and clarity.

The paragraph quoted above continues:

[tack] separates signals or groups of numerals that, if not separated, could convey a different meaning from that intended.

Example: If the signal SL2 means “Prepare to receive personnel casualties,” TACK would be inserted between the digit 2 and the given number of casualties: SL2 TACK 27.

In other words, in flag signalling, tack is a metacharacter, an extramessage separator. A comment later in the thread explains further:

To be precise however it's meant to separate terms so if you [have] two numbers in sequence such as: "twenty, two" it becomes "twenty tack two" and doesn't sound like "22".

If tack is treated as a metacharacter, it's slightly unclean to make it stand for the dash or hyphen that leads off an option specification in a command line, but people cope anyway.

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    It's neat that this was a navy term. But I've never, ever, ever heard it in 4 continents in decades of working in that field. Weird! Note that the description you provide, has utterly no connection to reading out a "minus sign". ("It separates signals or groups of numerals") it also has utterly no connection to Unix or computing. (Am I right? - pls correct if wrong.) I was famiiar with "tack" being used by naval men to "separate groups of numerals" ("who hasn't read Tom Clancy") but I just can't see any connection, even vaguely, with the minus sign that introduces options in Unix. – Fattie Aug 17 '14 at 19:35
  • (Note that, I guess .. say you were reading out a Unix command, where, for some reason, there were groups of numerals that needed to be separated. (A trivial example is a phone number .. 03, tack, 4324, tack, 1234.) I guess that would be a good way to use "tack", since, uh, "tack" is for "separating groups of numerals". It seems utterly bizarre to use it to represent the "options flag" in shell commands - weird one! (I didn't even think of the connection when I heard the lady reading in the video.) – Fattie Aug 17 '14 at 19:37
  • @JoeBlow, I don't find the option-flag use bizarre, but instead a problem because it stirs ambiguity into the meaning of tack as used in radio communication. The person receiving may wonder, “Should I write 20 and 2, or 20-2?” – James Waldby - jwpat7 Aug 17 '14 at 20:06
  • I recognize this post is over a year old but anecdotally this is how hyphens are pronounced in EVE Online. For example a system named like "A-23B" would be pronounced as "A tack two three B" or more briefly "A tack two" if that was unambiguous enough. – mfoy_ Sep 23 '15 at 20:59
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    In case anyone needs a source for this (4 years later!), TACK is made explicit in the NATO unclassified "MTP 1(D), VOLUME II MULTINATIONAL MARITIME TACTICAL SIGNAL AND MANEUVERING BOOK" (usna.edu/ypsquadron/_files/documents/MTP_2.pdf), Section 103.j – Centzon Mar 7 '18 at 7:59

The comment above is correct in that the term "tac" originated in the Navy, used as a flag separator. This made its way into the Unix environment as the options specified after a command are referred to as flags.

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I just heard "tack" for the first time in a 2017 Udemy video relating to a cyber-security tool called Nmap. The DOS/Windows command-line command was >nmap -O, and what would I ordinarily describe as "switch O"* to signal my experience is described by him as "tack O". Since the nmap tool is ubiquitous across platforms and in computer security classes, and hackers tend toward Linux, the instructor's usage is likely correct when using nmap on any platform. However, I bet dollars to donuts that the instructor would understand "switch O"--and sigh internally upon hearing "dash 0".

*note that in spoken English switch is ambiguous and can mean a forward slash (/) or a dash (-), so the dash is formally called an option. Options that are spelled out in a whole English word instead of a character have two dashes, and I know of no jargon-savvy way to call such options anything other than dash dash! Tack-tack, perhaps?

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