Path (computing)

 ( Computer File Systems ) 

A path (or filepath, file path, pathname, or similar) is a string that uniquely identifies an item in a hierarchical file system. Generally, a path is composed of directory names, special format specifiers, and optionally a filename, all separated by delimiters. This delimiter can vary by operating system, but popular, modern systems use the slash , backslash , or colon .

The case sensitivity of individual path components will vary based on operating system, or based on options specified at the time of a file system's mkfs or first use. In practice, this means that for a case-sensitive system, path components named and can coexist at the same level in the hierarchy, whereas for a case- insensitive file system, they cannot (an error will occur). macOS and Windows' native file systems are case-insensitive by default, whereas typical Linux file systems are case-sensitive. Includes a description of APFS, the default file system for macOS Windows file system treats file and directory names as case-insensitive. FOO.txt and foo.txt will be treated as equivalent files. Linux file system treats file and directory names as case-sensitive. FOO.txt and foo.txt will be treated as distinct files. Case sensitivity in Linux refers to files and directories recognizing differences between lowercase and uppercase characters in filenames. For instance, "File.txt" and "file.txt" would both be treated as two distinct files. This concept is integral to Unix-like operating systems, including Linux.

A path can be either relative or absolute. A relative path is a path in relation to another, most often the working directory. An absolute path indicates a location regardless of the current directory; that is, it specifies all path components starting from the file system's Root directory, and does not depend on context like a relative path does.

Paths are also essential for locating hierarchically-organized network resources, as seen in URLs and UNC paths.

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History Multics first introduced a hierarchical file system with directories (separated by ">") in the mid-1960s.

Around 1970, Unix introduced the slash as its directory separator.

Originally, MS-DOS did not support directories. When adding the feature, using the Unix standard of a slash was not a good option since many existing commands used a slash as the switch prefix (i.e., ). In contrast, Unix uses the dash as the switch prefix. The backslash was ultimately chosen instead for its similarity to the slash and not conflicting with existing commands. This convention continued into Windows. However, some areas of Windows do accept or understand Unix-style slashes also, such as PowerShell.

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Summary of systems The following table describes the syntax of paths in notable operating systems:

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In programming languages Most programming languages use the path representation of the underlying system, but some may also be system-independent.

For instance, this C code is system- dependent and may fail on opposing systems:

uxFile = fopen("project/readme.txt", "r") // Fails on Windows winFile = fopen("C:\\Program Files\\bin\\config.bat", "r") // Fails on Unix

• In Java, the field stores the system-dependent separator. Some functions preclude the need for the separator entirely.

import java.io.File;

import java.nio.file.Path; import java.nio.file.Paths; // ... File file = new File("path" + File.separator + "file.txt"); Path path = Paths.get("path", "file.txt");

• In Python, the module offers system-independent path operations.

from pathlib import Path

with (Path("path") / "to" / "file.txt").open() as open_file:

   ...
     

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In Unix Most Unix-like systems use a similar syntax. POSIX allows treating a path beginning with two slashes in an implementation-defined manner, though in other cases systems must treat consecutive slashes as one.

Many applications on Unix-like systems (for example, secure copy, rcp, and rsync) use resource definitions such as , or URI schemes with the service name (here 'smb'), like .

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In macOS When macOS was being developed, it inherited some pathname choices from Classic Mac OS and the Unix-like NeXTSTEP. The classic Mac OS uses a while Unix and Unix-like systems use a as the path delimiter. As a solution, to preserve compatibility for software and familiarity for users, and to allow disk file systems to be used both by the classic Mac OS and macOS, some portions of macOS convert between colons and slashes in pathnames; for example, the HFS+ file system, from the classic Mac OS, converts colons in file names to slashes and, when reading a directory, converts slashes in filenames to colons, and the Carbon toolkit converts colons in pathnames to slashes and slashes in path names to colons, and converts them back when providing filenames and pathnames to the caller.

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In DOS and Windows

DOS and Windows have no single root directory; a root exists for each storage drive, indicated with a drive letter or through UNC.

Directory and file name comparisons are case-insensitive: "test.TXT" would match "Test.txt".

Windows understands the following kinds of paths:

• Local paths, such as .
• Universal naming convention (UNC).
• DOS device paths, such as or . The first, skips path normalization. The second, uses the raw device namespace.

In the Windows API, file I/O functions automatically convert into (except when using the prefix). Paths using standard Windows APIs (dating back to DOS and Win9x), were limited to 260 characters, or less, as defined by the environment variable . For backwards compatibility with legacy applications this limitation was not removed until Windows 10, build 1607, when it could be expanded to 32,767. Windows NT always supported the 32,767 path length internally but only if using Unicode APIs or forcing UNC paths by the prefix.

PowerShell allows slash-interoperability for backwards-compatibility:

PS C:\>Get-Content -Path "C:/path/to/file.txt"

Here is some text within a file

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Yen/won character error

Japanese and Korean versions of Windows often displayed the '¥' character or the 'Won sign' character instead of the directory separator. This is because while in ANSI codepages, the character at 0x5C was the backslash, and in Japanese and Korean codepages, 0x5C was the yen and won signs, respectively. Therefore, when the character for a backslash was used, other glyphs appeared.

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Universal Naming Convention

The Microsoft Universal Naming Convention ( UNC, uniform naming convention, or network path), is a syntax to describe the location of a network resource, such as a shared file, directory, or printer. A UNC path has the general form:

Some Windows interfaces allow or require UNC syntax for WebDAV share access, rather than a URL. The UNC syntax is extended with optional components to denote use of SSL and TCP/IP port number. Thus, the WebDAV URL of becomes .

When viewed remotely, the "SharedFolder" may have a name different from what a program on the server sees when opening "\SharedFolder". Instead, the SharedFolder name consists of an arbitrary name assigned during creation of the share.

Since UNCs start with two backslashes, and the backslash is also used for Escape sequence and in regular expressions, cases of leaning toothpick syndrome may arise. An escaped string for a regular expression matching a UNC begins with 8 backslashes because the string and regular expression both require escaping. This can be simplified by using , such as in C#, in Python, or in Perl.

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See also

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Notes

Categories: Computer File Systems

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