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In computer science, control flow (or flow of control) is the order in which individual statements, instructions or function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an imperative programming language from a declarative programming language.
Shell variables, created using the set or @ statements, are internal to C shell. They are not passed to child processes. Shell variables can be either simple strings or arrays of strings. Some of the shell variables are predefined and used to control various internal C shell options, e.g., what should happen if a wildcard fails to match anything.
A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. [1] The various dialects of shell scripts are considered to be command languages . Typical operations performed by shell scripts include file manipulation, program execution, and printing text.
tcsh and sh shell windows on a Mac OS X Leopard [1] desktop. A Unix shell is a command-line interpreter or shell that provides a command line user interface for Unix-like operating systems. The shell is both an interactive command language and a scripting language, and is used by the operating system to control the execution of the system using ...
A scripting language is sometimes referred to as very high-level programming language if it operates at a high level of abstraction, or as a control language, particularly for job control languages on mainframes. The term scripting language is sometimes used in a wider sense, to refer to dynamic high-level programming
The shell's design was intentionally minimalistic; even the if and goto statements, essential for control of program flow, were implemented as separate commands. [1] The shell has no facilities for comments besides a builtin command :. Programmers simply write text after this command, which ignores all parameters and simply succeeds.
In Linux, if the script was executed by a regular user, the shell would attempt to execute the command rm -rf / as a regular user, and the command would fail. However, if the script was executed by the root user, then the command would likely succeed and the filesystem would be erased. It is recommended to use sudo on a per-command basis instead.
In computer programming, a loop counter is a control variable that controls the iterations of a loop (a computer programming language construct). It is so named because most uses of this construct result in the variable taking on a range of integer values in some orderly sequences (for example., starting at 0 and ending at 10 in increments of 1)