Translations by Anthony Fok

Enable and disable shell builtins. Enables and disables builtin shell commands. Disabling allows you to execute a disk command which has the same name as a shell builtin without using a full pathname. Options: -a print a list of builtins showing whether or not each is enabled -n disable each NAME or display a list of disabled builtins -p print the list of builtins in a reusable format -s print only the names of Posix `special' builtins Options controlling dynamic loading: -f Load builtin NAME from shared object FILENAME -d Remove a builtin loaded with -f Without options, each NAME is enabled. To use the `test' found in $PATH instead of the shell builtin version, type `enable -n test'. Exit Status: Returns success unless NAME is not a shell builtin or an error occurs.

Parse option arguments. Getopts is used by shell procedures to parse positional parameters as options. OPTSTRING contains the option letters to be recognized; if a letter is followed by a colon, the option is expected to have an argument, which should be separated from it by white space. Each time it is invoked, getopts will place the next option in the shell variable $name, initializing name if it does not exist, and the index of the next argument to be processed into the shell variable OPTIND. OPTIND is initialized to 1 each time the shell or a shell script is invoked. When an option requires an argument, getopts places that argument into the shell variable OPTARG. getopts reports errors in one of two ways. If the first character of OPTSTRING is a colon, getopts uses silent error reporting. In this mode, no error messages are printed. If an invalid option is seen, getopts places the option character found into OPTARG. If a required argument is not found, getopts places a ':' into NAME and sets OPTARG to the option character found. If getopts is not in silent mode, and an invalid option is seen, getopts places '?' into NAME and unsets OPTARG. If a required argument is not found, a '?' is placed in NAME, OPTARG is unset, and a diagnostic message is printed. If the shell variable OPTERR has the value 0, getopts disables the printing of error messages, even if the first character of OPTSTRING is not a colon. OPTERR has the value 1 by default. Getopts normally parses the positional parameters ($0 - $9), but if more arguments are given, they are parsed instead. Exit Status: Returns success if an option is found; fails if the end of options is encountered or an error occurs.

Display or execute commands from the history list. fc is used to list or edit and re-execute commands from the history list. FIRST and LAST can be numbers specifying the range, or FIRST can be a string, which means the most recent command beginning with that string. Options: -e ENAME select which editor to use. Default is FCEDIT, then EDITOR, then vi -l list lines instead of editing -n omit line numbers when listing -r reverse the order of the lines (newest listed first) With the `fc -s [pat=rep ...] [command]' format, COMMAND is re-executed after the substitution OLD=NEW is performed. A useful alias to use with this is r='fc -s', so that typing `r cc' runs the last command beginning with `cc' and typing `r' re-executes the last command. Exit Status: Returns success or status of executed command; non-zero if an error occurs.

Evaluate conditional expression. This is a synonym for the "test" builtin, but the last argument must be a literal `]', to match the opening `['.

Execute conditional command. Returns a status of 0 or 1 depending on the evaluation of the conditional expression EXPRESSION. Expressions are composed of the same primaries used by the `test' builtin, and may be combined using the following operators: ( EXPRESSION ) Returns the value of EXPRESSION ! EXPRESSION True if EXPRESSION is false; else false EXPR1 && EXPR2 True if both EXPR1 and EXPR2 are true; else false EXPR1 || EXPR2 True if either EXPR1 or EXPR2 is true; else false When the `==' and `!=' operators are used, the string to the right of the operator is used as a pattern and pattern matching is performed. When the `=~' operator is used, the string to the right of the operator is matched as a regular expression. The && and || operators do not evaluate EXPR2 if EXPR1 is sufficient to determine the expression's value. Exit Status: 0 or 1 depending on value of EXPRESSION.

Common shell variable names and usage. BASH_VERSION Version information for this Bash. CDPATH A colon-separated list of directories to search for directories given as arguments to `cd'. GLOBIGNORE A colon-separated list of patterns describing filenames to be ignored by pathname expansion. HISTFILE The name of the file where your command history is stored. HISTFILESIZE The maximum number of lines this file can contain. HISTSIZE The maximum number of history lines that a running shell can access. HOME The complete pathname to your login directory. HOSTNAME The name of the current host. HOSTTYPE The type of CPU this version of Bash is running under. IGNOREEOF Controls the action of the shell on receipt of an EOF character as the sole input. If set, then the value of it is the number of EOF characters that can be seen in a row on an empty line before the shell will exit (default 10). When unset, EOF signifies the end of input. MACHTYPE A string describing the current system Bash is running on. MAILCHECK How often, in seconds, Bash checks for new mail. MAILPATH A colon-separated list of filenames which Bash checks for new mail. OSTYPE The version of Unix this version of Bash is running on. PATH A colon-separated list of directories to search when looking for commands. PROMPT_COMMAND A command to be executed before the printing of each primary prompt. PS1 The primary prompt string. PS2 The secondary prompt string. PWD The full pathname of the current directory. SHELLOPTS A colon-separated list of enabled shell options. TERM The name of the current terminal type. TIMEFORMAT The output format for timing statistics displayed by the `time' reserved word. auto_resume Non-null means a command word appearing on a line by itself is first looked for in the list of currently stopped jobs. If found there, that job is foregrounded. A value of `exact' means that the command word must exactly match a command in the list of stopped jobs. A value of `substring' means that the command word must match a substring of the job. Any other value means that the command must be a prefix of a stopped job. histchars Characters controlling history expansion and quick substitution. The first character is the history substitution character, usually `!'. The second is the `quick substitution' character, usually `^'. The third is the `history comment' character, usually `#'. HISTIGNORE A colon-separated list of patterns used to decide which commands should be saved on the history list.

Set and unset shell options. Change the setting of each shell option OPTNAME. Without any option arguments, list all shell options with an indication of whether or not each is set. Options: -o restrict OPTNAMEs to those defined for use with `set -o' -p print each shell option with an indication of its status -q suppress output -s enable (set) each OPTNAME -u disable (unset) each OPTNAME Exit Status: Returns success if OPTNAME is enabled; fails if an invalid option is given or OPTNAME is disabled.