4.4. /usr/bin : Most user commands

4.4.1. Purpose

This is the primary directory of executable commands on the system.

4.4.2. Requirements

There must be no subdirectories in /usr/bin.

4.4.3. Specific Options

The following files, or symbolic links to files, must be in /usr/bin, if the corresponding subsystem is installed:

perlThe Practical Extraction and Report Language (optional)
pythonThe Python interpreted language (optional)
tclshSimple shell containing Tcl interpreter (optional)
wishSimple Tcl/Tk windowing shell (optional)
expectProgram for interactive dialog (optional)


In many executable scripts, the interpreter to be invoked to execute the script is specified using #!path_to_interpreter on the first line of a script. To make such scripts portable among different systems, it is advantageous to standardize the interpreter locations. The shell interpreter is already fixed in /bin by this specification, but interpreters for Perl, Python, Tcl and expect may be installed in various places. The locations specified here may be implemented as symbolic links to the physical location of the interpreters.