Glob (programming)

In computer programming, glob patterns specify sets of filenames with wildcard characters. For example, the Unix Bash shell command mv *.txt textfiles/ moves (mv) all files with names ending in codice_1 from the current directory to the directory codice_2. Here, codice_3 is a wildcard standing for "any string of characters" and codice_4 is a glob pattern. The other common wildcard is the question mark (codice_5), which stands for one character. For example, mv ?.txt shorttextfiles/ will move all files named with a single character followed by codice_1 from the current directory to directory codice_7, while ??.txt would match all files whose name consists of 2 characters followed by codice_1.
In addition to matching filenames, globs are also used widely for matching arbitrary strings (wildcard matching). In this capacity a common interface is codice_9.
Origin.
The glob command, short for "global", originates in the earliest versions of Bell Labs' Unix. The command interpreters of the early versions of Unix (1st through 6th Editions, 1969–1975) relied on a separate program to expand wildcard characters in unquoted arguments to a command: "/etc/glob". That program performed the expansion and supplied the expanded list of file paths to the command for execution.
Glob was originally written in the B programming language. It was the first piece of mainline Unix software to be developed in a high-level programming language. Later, this functionality was provided as a C library function, codice_10, used by programs such as the shell. It is usually defined based on a function named codice_11, which tests for whether a string matches a given pattern - the program using this function can then iterate through a series of strings (usually filenames) to determine which ones match. Both functions are a part of POSIX: the functions defined in POSIX.1 since 2001, and the syntax defined in POSIX.2. The idea of defining a separate match function started with wildmat (wildcard match), a simple library to match strings against Bourne Shell globs.
Traditionally, globs do not match hidden files in the form of Unix dotfiles; to match them the pattern must explicitly start with codice_12. For example, codice_3 matches all visible files while codice_14 matches all hidden files.
Syntax.
The most common wildcards are , , and .
Normally, the path separator character ( on Linux/Unix, MacOS, etc. or on Windows) will never be matched. Some shells, such as Bash have functionality allowing users to circumvent this. 
Unix-like.
On Unix-like systems , is defined as above while has two additional meanings:
The ranges are also allowed to include pre-defined character classes, equivalence classes for accented characters, and collation symbols for hard-to-type characters. They are defined to match up with the brackets in POSIX regular expressions.
Unix globbing is handled by the shell per POSIX tradition. Globbing is provided on filenames at the command line and in shell scripts. The POSIX-mandated codice_15 statement in shells provides pattern-matching using glob patterns.
Some shells (such as the C shell and Bash) support additional syntax known as alternation or brace expansion. Because it is not part of the glob syntax, it is not provided in codice_15. It is only expanded on the command line before globbing.
The Bash shell also supports the following extensions:
Windows and DOS.
The original DOS was a clone of CP/M designed to work on Intel's 8088 and 8086 processors. Windows shells, following DOS, do not traditionally perform any glob expansion in arguments passed to external programs. Shells may use an expansion for their own builtin commands:
Windows and DOS programs receive a long command-line string instead of argv-style parameters, and it is their responsibility to perform any splitting, quoting, or glob expansion. There is technically no fixed way of describing wildcards in programs since they are free to do what they wish. Two common glob expanders include:
Most other parts of Windows, including the Indexing Service, use the MS-DOS style of wildcards found in CMD. A relic of the 8.3 filename age, this syntax pays special attention to dots in the pattern and the text (filename). Internally this is done using three extra wildcard characters, . On the Windows API end, the equivalent is , and corresponds to its underlying . (Another fnmatch analogue is .) Both open-source msvcrt expanders use , so 8.3 filename quirks will also apply in them.
SQL.
The SQL operator has an equivalent to and but not .
Standard SQL uses a glob-like syntax for simple string matching in its codice_18 operator, although the term "glob" is not generally used in the SQL community. The percent sign () matches zero or more characters and the underscore () matches exactly one.
Many implementations of SQL have extended the codice_18 operator to allow a richer pattern-matching language, incorporating character ranges (), their negation, and elements of regular expressions.
Compared to regular expressions.
Globs do not include syntax for the Kleene star which allows multiple repetitions of the preceding part of the expression; thus they are not considered regular expressions, which can describe the full set of regular languages over any given finite alphabet.
Globs attempt to match the entire string (for example, matches S.DOC and SA.DOC, but not POST.DOC or SURREY.DOCKS), whereas, depending on implementation details, regular expressions may match a substring.
Implementing as regular expressions.
The original Mozilla proxy auto-config implementation, which provides a glob-matching function on strings, uses a replace-as-RegExp implementation as above. The bracket syntax happens to be covered by regex in such an example.
Python's fnmatch uses a more elaborate procedure to transform the pattern into a regular expression.
Other implementations.
Beyond their uses in shells, globs patterns also find use in a variety of programming languages, mainly to process human input. A glob-style interface for returning files or an fnmatch-style interface for matching strings are found in the following programming languages: