| If the shell is invoked by exec(2), and the first character of argument zero ($0) is -, then the shell is assumed to be a login shell and commands are read from /etc/profile and then from either .profile in the current directory or $HOME/.profile, if either file exists. Next, for interactive shells, commands are read from the file named by performing parameter expansion, command substitution, and arithmetic substitution on the value of the environment variable ENV if the file exists. If the -s option is not present and arg is, then a path search is performed on the first arg to determine the name of the script to execute. The script arg must have read permission and any setuid and setgid settings will be ignored. If the script is not found on the path, arg is processed as if it named a built-in command or function. Commands are then read as described below; the following options are interpreted by the shell when it is invoked: | -c | If the -c option is present, then commands are read from the first arg. Any remaining arguments become positional parameters starting at 0. | | -s | If the -s option is present or if no arguments remain, then commands are read from the standard input. Shell output, except for the output of the special commands listed earlier in this appendix, is written to file descriptor 2. | | -i | If the -i option is present or if the shell input and output are attached to a terminal (as told by tcgetattr(2)), then this shell is interactive. In this case TERM is ignored (so that kill 0 does not kill an interactive shell) and INTR is caught and ignored (so that wait is interruptible). In all cases, QUIT is ignored by the shell. | | -r | If the -r option is present, the shell is a restricted shell. | | -D | A list of all double quoted strings that are preceded by a $ will be printed on standard output and the shell will exit. This set of strings will be subject to language translation when the locale is not C or POSIX. No commands will be executed. | | -I filename | The -R filename option is used to generate a cross reference database that can be used by a separate utility to find definitions and references for variables and commands. |
The remaining options and arguments are described under the set command above. An optional - as the first argument is ignored. |
