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Wrapper scripts often use this command to run a program (either directly or through an interpreter or virtual machine) after setting environment variables or other configuration. By using exec, the resources used by the shell program do not need to stay in use after the program is started. [2] The exec command can also perform a redirection.
JP Software command-line processors provide user-configurable colorization of file and directory names in directory listings based on their file extension and/or attributes through an optionally defined %COLORDIR% environment variable. For the Unix/Linux shells, this is a feature of the ls command and the terminal.
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. [2]
A high-level overview of the Linux kernel's system call interface, which handles communication between its various components and the userspace. In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system [a] on which it is executed.
Bash can execute the vast majority of Bourne shell scripts without modification, with the exception of Bourne shell scripts stumbling into fringe syntax behavior interpreted differently in Bash or attempting to run a system command matching a newer Bash builtin, etc. Bash command syntax includes ideas drawn from the Korn Shell (ksh) and the C ...
The interpreter would execute one of a number of predefined commands, one of which would be to run a user program. Common commands would log the user on and off the system, allocate, free, and manipulate devices and files, and query various pieces of information about the system or a user process. [6]
The term user space (or userland) refers to all code that runs outside the operating system's kernel. [2] User space usually refers to the various programs and libraries that the operating system uses to interact with the kernel: software that performs input/output , manipulates file system objects, application software , etc.
Therefore, shell builtins are usually used for simple, almost trivial, functions, such as text output. Because of the nature of some operating systems, some functions of the systems must necessarily be implemented as shell builtins. The most notable example is the cd command, which changes the working directory of the shell.