Experts differ regarding what defines a scripting language and what defines a programming language. It’s clear that languages such as Python blur the old distinction between programming and scripting.

Originally, scripting was writing small files of commands that invoked other system commands. For example, you could write a script that wraps the Linux file command. Scripts were executed by scripting-language interpreters that parsed each command one at a time and then executed the command.

Modern scripting languages, such as Tcl, are parsed at runtime and compiled into an internal bytecode format. Once compiled, there is no real difference from a language associated with programming such as Java.

With a scripting language

*You generally don’t have to compile the script in advance. The scripting language interpreter may compile the program, often to an internal byte code, but you don’t have to invoke a compiler as a separate step.

*The facilities of the language generally provide a higher level and more abstract level of interaction with the system than with programming languages. For example, writing socket-based networking code in Tcl requires a lot less code than writing the same code in a programming language such as C. Tcl provides a more abstract view of networking; therefore, your code is a lot simpler.

*The commands in the scripting language are mostly the commands available to you on the command line. Scripting languages introduce their own commands, too.

*The language is generally identified as a scripting language. This is more consensus than anything else. Forth is considered an interpreted programming language, while Perl is considered a scripting language.

Table 15-1 lists some of the more common scripting and programming languages. Note that these are the generally-accepted categories for these languages, not hard and fast rules. This should not stop you, for example, from writing programs in Perl or Python. The distinctions between programming and scripting have blurred in recent years.

Table 15-1 Common Scripting Languages and Common Programming Languages