su

Description

su is used to become another user during a login session. Invoked without a username, su defaults to becoming the super user. The optional argument - may be used to provide an environment similar to what the user would expect had the user logged in directly.

The user will be prompted for a password, if appropriate. Invalid passwords will produce an error message. All attempts, both valid and invalid, are logged to detect abuses of the system. Applications may not assume the format of prompts and anticipated input for user interaction, because they are unspecified.

An optional command can be executed. This is done by the shell specified in /etc/passwd for the target user unless the -s or -m options are used. Any arguments supplied after the username will be passed to the invoked shell (shell shall support the -c command line option in order for a command to be passed to it).

The current environment is passed to the new shell. The value of PATHis reset to /bin:/usr/bin for unprivileged users, or /sbin:/bin:/usr/sbin:/usr/bin for users with appropriate privilege. This may be changed with the ENV_PATH and ENV_SUPATH definitions in /etc/login.defs. When using the -m or -p options, the user's environment is not changed.

A subsystem login is indicated by the presence of a "*" as the first character of the login shell. If this character is present, it shall be removed, and the remaining path (or /bin/sh if the remaining path is empty) shall be executed after changing the root directory to the directory specified as the home directory.

Standard Options