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In computing, command substitution is a facility that allows a command to be run and its output to be pasted back on the command line as arguments to another command. . Command substitution first appeared in the Bourne shell, [1] introduced with Version 7 Unix in 1979, and has remained a characteristic of all later Uni
An MS-DOS command line, illustrating parsing into command and arguments. A command-line argument or parameter is an item of information provided to a program when it is started. [20] A program can have many command-line arguments that identify sources or destinations of information, or that alter the operation of the program.
In MS-DOS, a batch file can be started from the command-line interface by typing its name, followed by any required parameters and pressing the ↵ Enter key. When DOS loads, the file AUTOEXEC.BAT, when present, is automatically executed, so any commands that need to be run to set up the DOS environment may be placed in this file.
For example, the diff command operates on two files at a time. The -n option to xargs specifies how many arguments at a time to supply to the given command. The command will be invoked repeatedly until all input is exhausted. Note that on the last invocation one might get fewer than the desired number of arguments if there is insufficient input.
Background execution allows a shell to run a command without user interaction in the terminal, freeing the command line for additional work with the shell. POSIX shells and other Unix shells allow background execution by using the & character at the end of command. In PowerShell, the Start-Process [43] or Start-Job [44] cmdlets can be used.
The runas command was introduced with the Windows 2000 operating system. [2] Any application can use this API to create a process with alternate credentials, for example, Windows Explorer in Windows 7 allows an application to be started under a different account if the shift key is held while right clicking its icon.
Command-line completion allows the user to type the first few characters of a command, program, or filename, and press a completion key (normally Tab ↹) to fill in the rest of the item. The user then presses Return or ↵ Enter to run the command or open the file.
Different command-line argument parsing methods are used by different programming languages to parse command-line arguments. Programming languages. C C uses ...