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The test command in Unix evaluates the expression parameter. In most recent shell implementations, it is a shell builtin, even though the external version still exists.In the second form of the command, the [ ] (brackets) must be surrounded by blank spaces (this is because [is a program and POSIX compatible shells require a space between the program name and its arguments).
In computing, which is a command for various operating systems used to identify the location of executables. The command is available in Unix and Unix-like systems, the AROS shell, [4] for FreeDOS [5] and for Microsoft Windows. [2] The functionality of the which command is similar to some implementations of the type command.
The true command is sometimes substituted with the very similar null command, [1] written as a single colon (:). The null command is built into the shell, and may therefore be more efficient if true is an external program (true is usually a shell built in function). We can rewrite the upper example using : instead of true:
This is a list of commands from the GNU Core Utilities for Unix environments. These commands can be found on Unix operating systems and most Unix-like operating systems. GNU Core Utilities include basic file, shell and text manipulation utilities. Coreutils includes all of the basic command-line tools that are expected in a POSIX system.
Bash, short for Bourne-Again SHell, is a shell program and command language supported by the Free Software Foundation [7] and first developed for the GNU Project [8] by Brian Fox. [9] Designed as a 100% [ 10 ] free software alternative for the Bourne shell , [ 11 ] [ 12 ] [ 13 ] it was initially released in 1989. [ 14 ]
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 shell scripts .
getopts is a built-in Unix shell command for parsing command-line arguments. It is designed to process command line arguments that follow the POSIX Utility Syntax Guidelines, based on the C interface of getopt. The predecessor to getopts was the external program getopt by Unix System Laboratories.
The most notable example is the cd command, which changes the working directory of the shell. Since each executable program runs in a separate process , and working directories are specific to each process, loading cd as an external program would not affect the working directory of the shell that loaded it.