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The Unix command su, which stands for 'substitute user' [1] [2] (or historically 'superuser' [3] [4]), is used by a computer user to execute commands with the privileges of another user account. When executed it invokes a shell without changing the current working directory or the user environment.
The current Linux manual pages for su define it as "substitute user", [9] making the correct meaning of sudo "substitute user, do", because sudo can run a command as other users as well. [10] [11] Unlike the similar command su, users must, by default, supply their own password for
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. It is recommended to use sudo on a per-command basis instead.
The remote shell (rsh) is a command-line computer program that can execute shell commands as another user, and on another computer across a computer network. The remote system to which rsh connects runs the rsh daemon (rshd). The daemon typically uses the well-known Transmission Control Protocol (TCP) port number 513.
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. [7]
Support for command history means that a user can recall a previous command into the command-line editor and edit it before issuing the potentially modified command. Shells that support completion may also be able to directly complete the command from the command history given a partial/initial part of the previous command.
Command-line interpreters allow users to issue various commands in a very efficient (and often terse) way. This requires the user to know the names of the commands and their parameters, and the syntax of the language that is interpreted. The Unix #! mechanism and OS/2 EXTPROC command facilitate the passing of batch files to external processors ...
Modern Unix systems generally use user groups as a security protocol to control access privileges. The wheel group is a special user group used on some Unix systems, mostly BSD systems, [citation needed] to control access to the su [4] [5] or sudo command, which allows a user to masquerade as another user (usually the super user).