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This page is about the meaning of symbols and certain single letters. For information about how the enter Special Characters such as © and ¶ please see that page.

^ (caret)

Caret is short-hand for the control key. For example, "^C" would mean, "press ctrl C'', I.E. hold ctrl while typing "C". This is a classical UNIX documentation convention which is eschewed by The Hub in favor of indicating the characters in square brackets

# (hash)

Hash, also known as "octothorpe" can mean several things, it can mean "pounds", it can be used as an improper substitute for ♯ and can mean the same as №. In some UNIX and Windows configuration files, such as the host file, # at the beginning of a line means a "comment", I.E. that line is only for information purposes and its contents are ignored. It can also refer to an HTML anchor, which is an HTML "anchor" tag that refers to a specific place in an HTML document. This only applies when used in URIs

@ (at sign)

At sign indicates which host a user is to be found at. For example: you@frontios.vistua.net means the user "you" on the machine "frontios" in the domain "vistua.net". @ signs are most commonly to be found in internet email addresses¹ to indicate which mailbox the mail should go to. Finger, FTP, SSH and certain other UNIX programs use identical syntax to refer to specific UNIX accounts, technically this is actually the same thing.

$ (dollar sign)

For historical reasons, $ sign refers to variables in many programming languages and in the UNIX shell. Variables are "placeholders" that refer to assigned values, similarly to variables in algebra. In some languages % serves this purpose. Most UNIX shells also end their command prompt with a $

& (ampersand)

The Ampersand can mean "and" as well as refer to a "XML Entity" which is a way of encoding special symbols into webpages, for example © would produce ©. In most UNIX shells, a double ampersand is used to execute multiple commands in succession with one command line, provided that each previous command succedes.

* (asterisk)

In most operating systems, including Windows and UNIX, * indicates the "anything-wildcard". I.E. "kid*" refers to any filename that begins with kid, "*kid", any filename that ends with kid and *kid* any filename that contains kid. On UNIX a single, solitary, * refers to "all files in the current directory", "*.*" serves that purpose on DOS/Windows.

- (hyphen)

Often confused with en and em dashes, the hyphen, colloquially referred to as dash begins a command-line flag on UNIX. For example, ls -l means, "execute the ls command with the flag "lowercase-L". (L means "long listing style" in this context).\\ For certain programs written by the Free Software Foundation, and other groups following the "GNU" style, flags that are words, not single letters are prefixed with a double dash for disambiguation. For example, tar --lzma means, run tar with the flag "lzma". This is because, technically, tar -lzma could be interpreted as the same as tar -l -z -m -a because classically UNIX has allowed single letter flags to be combined that way. However, this style is not universal. Many programs that have both single-letter flags and whole-word flags only use the single dash.

M (capital English M)

For arcane historical reasons, in some older UNIX and OpenVMS documentation the M followed by a dash refers to the "alt" key. For example, "press M-x" means, "press alt X". Most modern documentation eschews this format due to it being stupid and referring to a type of keyboard that is now extremely rare. (For further information, please consult Wikipedia:Meta_key.)

Notes

¹ A very, very, long time ago. Some emails were not sent over the internet, but relayed over a system called UUCP (Unix to Unix CoPy), in this case exclaimation marks (!) were used for a similar purpose

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