Unix Command Language: sh/bash/zsh
The UNIX shell is most people's main access to the UNIX operating system. The Bourne shell (sh) and it's decenents (bash/zsh) have a strong and powerful syntactical language built in supplying various features usually found only in more sophisticated general-purpose programming languages, such as control-flow constructs, variables, comments, arrays, subroutines, and so on. With these sorts of features available, it is possible to write reasonably sophisticated applications as shell scripts. Often, writing a shell script is much quicker than writing the equivalent code in other programming languages. The many advantages include easy program or file selection, quick start, and interactive debugging. A shell script can be used to provide a sequencing and decision-making linkage around existing programs, and for moderately-sized scripts the absence of a compilation step is an advantage. Interpretive running makes it easy to write debugging code into a script and rerun it to detect and fix bugs. Non-expert users can use scripting to tailor the behavior of programs, and shell scripting provides some limited scope for multiprocessing.