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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).
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.
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.
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 .
pexec is a command-line utility for Linux and other Unix-like operating systems which allows the user to execute shell commands in parallel. The specified code can be executed either locally or on remote hosts, in which case ssh is used to build a secure tunnel between them. Similar to shell loops, a variable is changed as the loop starting the ...
The C shell is a command processor which is typically run in a text window, allowing the user to type and execute commands. The C shell can also read commands from a file, called a script . Like all Unix shells, it supports filename wildcarding , piping , here documents , command substitution , variables and control structures for condition ...
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).
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.