globbing

Globbing is a pattern matching technique used for filename expansion in many shell environments and programming languages. A glob pattern is a string that contains wildcard characters, which the shell expands into a list of matching file names before the command is executed. This simplifies referring to groups of files without listing them individually.

The most common metacharacters are the asterisk *, which matches any sequence of characters; the question mark ?, which matches exactly one character; and character classes such as [a-z], which match any one character from the enclosed set. Some shells also support negated classes like [^...], and extended patterns under specialized settings (for example, bash extglob or brace expansion). Patterns may be combined, and the exact rules can vary between platforms.

How globbing works: the shell scans the command for glob patterns, queries the file system for names that match, and replaces the pattern with the resulting list. If no file matches, behavior varies by shell: some options treat the pattern as a literal, others report an error. Some environments offer options such as nullglob to treat unmatched patterns as empty results.

Examples: ls *.txt lists all text files in the current directory; cp /path/to/images/*.jpg /backup/ copies all JPEG files from that directory. In programming languages, modules such as Python's glob or Java's NIO glob support similar patterns for locating files.

Globbing is distinct from regular expressions; it provides a simpler, file-system oriented syntax designed for expanding filenames rather than matching arbitrary string structures. It is widely implemented in shells and language libraries, with variations in syntax and behavior across platforms.