Pathnames

Pathnames are strings that designate the location of a resource within a hierarchical namespace, most commonly a filesystem. They can be absolute, which specifies a location from the root, or relative, describing a location from the current working directory. Pathnames are made up of components separated by a delimiter: typically a forward slash on POSIX systems or a backslash on Windows, though many environments accept forward slashes in general.

A typical pathname contains a root indicator (such as / on POSIX, or a drive letter like C:\ on Windows), followed by one or more directory names and, finally, a resource name such as a file. Special components may appear: . denotes the current directory, and .. denotes the parent directory; consecutive separators are usually treated as a single separator.

Different platforms have different conventions. POSIX pathnames use / as the separator and treat file names as case-sensitive; Windows pathnames can use \ or / as the separator and often are case-insensitive. URL paths are a related concept where the portion after the domain describes nested resources, separated by /.

Pathnames are subject to resolution rules. Some components may be symbolic or junction links that redirect to other locations, requiring normalization to obtain a canonical path. Absolute vs relative paths, symbolic links, and mount points can affect what a given pathname refers to.

In programming, pathnames are manipulated by library functions that join, normalize, split, and resolve components, with care to avoid security risks such as path traversal vulnerabilities when accepting user input.