When the end of options is encountered, getopts exits with a return value greater than zero. OPTIND is set to the index of the first non-option argument, and name is set to ‘?’. getopts normally parses the positional parameters, but if more arguments are given in args, getopts parses those instead. getopts can report errors in two ways. If the first character of optstring is a colon, silent error reporting is used. In normal operation, diagnostic messages are printed when invalid options or missing option arguments are encountered.
If the variable OPTERR is set to 0, no error messages will be displayed, even if the first character of optstring is not a colon.
If an invalid option is seen, getopts places ‘?’ into name and, if not silent, prints an error message and unsets OPTARG. If getopts is silent, the option character found is placed in OPTARG and no diagnostic message is printed.
If a required argument is not found, and getopts is not silent, a question mark
(‘?’) is placed in name, OPTARG is unset, and a diagnostic message is printed. If getopts is silent, then a colon (‘:’) is placed in name and OPTARG is set to the option character found. hash hash [-r] [-p filename] [-dt] [name]
Each time hash is invoked, it remembers the full pathnames of the commands specified as name arguments, so they need not be searched for on subsequent invocations. The commands are found by searching through the directories listed in $PATH. Any previously-remembered pathname is discarded. The -p option inhibits the path search, and filename is used as the location of name.
The -r option causes the shell to forget all remembered locations. The -d option causes the shell to forget the remembered location of each name. If the
-t option is supplied, the full pathname to which each name corresponds is printed. If multiple name arguments are supplied with -t the name is printed before the hashed full pathname. The -l option causes output to be displayed in a format that may be reused as input. If no arguments are given, or if only -l is supplied, information about remembered commands is printed. The return status is zero unless a name is not found or an invalid option is supplied. pwd pwd [-LP]
Print the absolute pathname of the current working directory. If the -P option is supplied, the pathname printed will not contain symbolic links. If the -L option is supplied, the pathname printed may contain symbolic links. The return status is zero unless an error is encountered while determining the name of the current directory or an invalid option is supplied. readonly readonly [-aAf] [-p] [name[=value]] ...
Mark each name as readonly. The values of these names may not be changed by subsequent assignment. If the -f option is supplied, each name refers to