glob (programming)

glob() (/ɡlɒb/) is a <a href="/facts/C_standard_library/qdG1nW2c">libc</a> function for globbing, which is the archetypal use of pattern matching against the <a href="/facts/File_system/FdPm90uc">names in a filesystem directory</a> such that a name pattern is expanded into a list of names matching that pattern. Although globbing may now refer to glob()-style pattern matching of any string, not just expansion into a list of filesystem names, the original meaning of the term is still widespread.
The glob() function and the underlying gmatch() function originated at <a href="/facts/Bell_Labs/fKP5Gk0H">Bell Labs</a> in the early 1970s alongside the original <a href="/facts/Research_Unix/5oWmUdwo">AT&T UNIX</a> itself and had a formative influence on the syntax of UNIX command line utilities and therefore also on the present-day reimplementations thereof. 
In their original form, glob() and gmatch() derived from code used in <a href="/facts/Bell_Labs/fKP5Gk0H">Bell Labs</a> in-house utilities that developed alongside the original Unix in the early 1970s. Among those utilities were also two command line tools called glob and <a href="/facts/Find_(Unix)/bg18ASlI">find</a>; each could be used to pass a list of matching filenames to other command line tools, and they shared the backend code subsequently formalized as glob() and gmatch(). Shell-statement-level globbing by default became commonplace following the <a href="/facts/Shell_builtin/9o8PrWpa">"builtin"-integration</a> of globbing-functionality into the <a href="/facts/Version_7_Unix/ju5nRs7k">7th edition</a> of the <a href="/facts/Unix_shell/2G4T2Fb9">Unix shell</a> in 1978. The Unix shell's -f option to disable globbing — i.e. revert to literal "file" mode — appeared in the same version.
The glob pattern quantifiers now standardized by <a href="/facts/POSIX/mQkSt234">POSIX.2</a> (IEEE Std 1003.2) fall into two groups, and can be applied to any character sequence ("string"), not just to directory entries.

<ul><li>"Metacharacters" (also called "Wildcards"):
<ul><li>? (not in brackets) matches any character exactly once.</li>
<li>* (not in brackets) matches a string of zero or more characters.</li></ul></li>
<li>"Ranges/sets":
<ul><li>[...], where the first character within the brackets is not '!', matches any single character among the characters specified in the brackets. If the first character within brackets is '!', then the [!...] matches any single character that is not among the characters specified in the brackets.</li></ul></li></ul>
The characters in the brackets may be a list ([abc]) or a range ([a-c]) or denote a character class (like [[:space:]] where the inner brackets are part of the classname). POSIX does not mandate multi-range ([a-c0-3]) support, which derive originally from <a href="/facts/Regular_expressions/KFL3veHX">regular expressions</a>.
As reimplementations of <a href="/facts/Bell_Labs/fKP5Gk0H">Bell Labs</a>' UNIX proliferated, so did reimplementations of its Bell Labs' libc and shell, and with them glob() and globbing. Today, glob() and globbing are standardized by the <a href="/facts/POSIX/mQkSt234">POSIX.2</a> specification and are integral part of every Unix-like libc ecosystem and shell, including AT&T Bourne shell-compatible <a href="/facts/Korn_shell/MMp8fQ4A">Korn shell (ksh)</a>, <a href="/facts/Z_shell/VhqrFpq0">Z shell (zsh)</a>, <a href="/facts/Almquist_shell/jnS95YW5">Almquist shell (ash)</a> and its derivatives and reimplementations such as <a href="/facts/Busybox/CRv85u7S">busybox</a>, <a href="/facts/Toybox/aLGYht2Q">toybox</a>, <a href="/facts/Bash_(Unix_shell)/RrYLtEJT">GNU bash</a>, <a href="/facts/Debian/cBd93qfJ">Debian dash</a>.

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glob (programming)