Pathname

A pathname is a string that identifies a location within a hierarchical namespace, such as a file system. It specifies how to traverse directories to reach a file or directory. Pathnames can be absolute (starting from the root) or relative (based on the current working directory). The components are typically directory names separated by a separator and ending with a final element that may be a directory or a file name.

In Unix-like systems, the separator is a forward slash, absolute paths start with /. In Windows, backslashes are used, and pathnames may begin with a drive letter (C:\) or use UNC syntax for network resources (\\server\share). URLs also contain pathnames after the domain, using slash separators and percent-encoding.

Pathname semantics include special components like .. to move to the parent directory and . for the current directory. Normalization resolves redundant separators and symbolic links or junctions into a canonical form. Some systems offer functions such as realpath or GetFullPathName to obtain the absolute, canonical path. Pathname resolution can be affected by mounted filesystems and access permissions.

In practice, pathnames are used by shells, programming languages, and applications to locate files, modules, or resources. Security considerations include preventing path traversal attacks by validating or sanitizing input and using canonicalized paths. Also, the term pathname is sometimes used interchangeably with file path or URL path in common language.