Command line interpreter
Examples of command line interpreters
- the various Unix shell programs such as Bash
- command.com (DOS, Windows).
- cmd.exe (OS/2, Windows NT)
- 4NT (Windows NT)
- TSO under MVS
- CMS under VM/CMS
- CL for OS/400
Command interpreters as user interfaces
Command line interpreters allow users to issue a lot of commands in a very efficient (and often terse) way. This requires the user to know the names of the commands and their parameters, and the syntax of the language that is interpreted.
graphical user interfaces were developed to provide an alternative user interface where commands were issued as pictorial operations, rather than as textual descriptions. For some complex tasks they are more difficult to use than a command line interface, because of the large number of menus and dialog boxes presented, and the innate difficulty of representing the underlying task pictorially.
Most command line interpreters support scripting, to various extents. (They are, after all, interpreters of an interpreted programming language, albeit that in many cases the language is unique to the particular command line interpreter.) They will interpret scripts (variously termed shell scripts or batch files) written in the language that they interpret. Some command line interpreters also incorporate the interpreter engines of other languages, such as REXX, in addition to their own, allowing the executing of scripts, in those languages, directly within the command line interpreter itself.
Conversely, scripting programming languages, in particular those with an eval function (such as REXX, Perl, Python, or Jython), can be used to implement command line interpreters. For a few operating systems, most notably DOS, such a command interpreter provides a more flexible Command line interface than the one supplied. In other cases, such a command interpreter can present a highly customised user interface employing the user interface and input/output facilities of the language.