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In computer science, a for-loop or for loop is a control flow statement for specifying iteration. Specifically, a for-loop functions by running a section of code repeatedly until a certain condition has been satisfied. For-loops have two parts: a header and a body. The header defines the iteration and the body is the code executed once per ...
Editing a FreeBSD shell script for configuring ipfirewall. 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 ...
"Bourne introduced control flows, loops, and variables into scripts, providing a more functional language to interact with the operating system (both interactively and noninteractively). The shell also permitted you to use shell scripts as filters, providing integrated support for handling signals, but lacked the ability to define functions.
For example, the following shell script repeats the echo hello loop until interrupted: while true do echo hello done The commands can be used to ignore the success or failure of a sequence of other commands, as in the example:
In computing, a shell is a computer program that exposes an operating system's services to a human user or other programs. In general, operating system shells use either a command-line interface (CLI) or graphical user interface (GUI), depending on a computer's role and particular operation.
Thus the shell itself is doing no direct processing of the data flowing through the pipeline. However, it's possible for the shell to perform processing directly, using a so-called mill or pipemill (since a while command is used to "mill" over the results from the initial command). This construct generally looks something like:
Rc uses C-like control structures instead of the original Bourne shell's ALGOL-like structures, except that it uses an if not construct instead of else, and has a Bourne-like for loop to iterate over lists. In rc, all variables are lists of strings, which eliminates the need for constructs like "$@". Variables are not re-split when expanded.
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 ...