PATH (variable)

Source: Wikipedia, the free encyclopedia.

PATH is an

directories where executable programs are located. In general, each executing process or user session
has its own PATH setting.

History

Version 3 Unix the directory was too large and /usr/bin, and a search path, became part of the operating system.[1]

Unix and Unix-like

On POSIX and Unix-like operating systems, the $PATH variable is specified as a list of one or more directory names separated by colon (:) characters.[2][3] Directories in the PATH-string are not meant to be escaped, making it impossible to have directories with : in their name.[4]

The /bin, /usr/bin, and /usr/local/bin directories are typically included in most users' $PATH setting (although this varies from implementation to implementation). The

tarbomb
. In that case, executing such a program requires specifying an absolute (/home/userjoe/bin/script.sh) or relative path (./script.sh) on the command line.

When a command name is specified by the user or an

exec call is made from a program, the system searches through $PATH, examining each directory from left to right in the list, looking for a filename that matches the command name. Once found, the program is executed as a child process
of the command shell or program that issued the command.

DOS, OS/2, and Windows

On DOS, OS/2, and Windows operating systems, the %PATH% variable is specified as a list of one or more directory names separated by semicolon (;) characters.[5]

The Windows system directory (typically C:\WINDOWS\system32) is typically the first directory in the path, followed by many (but not all) of the directories for installed software packages. Many programs do not appear in the path as they are not designed to be executed from a

Graphical User Interface. Some programs may add their directory to the front of the PATH variable's content during installation, to speed up the search process and/or override OS commands. In the DOS era, it was customary to add a PATH {program directory};%PATH% or SET PATH={program directory};%PATH% line to AUTOEXEC.BAT
.

When a command is entered in a command shell or a system call is made by a program to execute a program, the system first searches the

EXE or COM, and batch scripts have extensions of BAT or CMD
. Other executable filename extensions can be registered with the system as well.

Once a matching executable file is found, the system spawns a new process that runs it.

The PATH variable makes it easy to run commonly used programs located in their own folders. If used unwisely, however, the value of the PATH variable can slow down the operating system by searching too many locations, or invalid locations.

Invalid locations can also stop services from running altogether, especially the 'Server' service which is usually a dependency for other services within a Windows Server environment.

References