bashのヘルプ

help, type, command, builtin, function, local, declare とか。

$ help help

help: help [-s] [pattern ...]

     Display helpful information about builtin commands.  If PATTERN is

    specified, gives detailed help on all commands matching PATTERN,

    otherwise a list of the builtins is printed.  The -s option

    restricts the output for each builtin command matching PATTERN to

    a short usage synopsis.
$ help type

type: type [-afptP] name [name ...]

     For each NAME, indicate how it would be interpreted if used as a

    command name.
    If the -t option is used, `type' outputs a single word which is one of

    `alias', `keyword', `function', `builtin', `file' or `', if NAME is an

    alias, shell reserved word, shell function, shell builtin, disk file,

    or unfound, respectively.
    If the -p flag is used, `type' either returns the name of the disk

    file that would be executed, or nothing if `type -t NAME' would not

    return `file'.
    If the -a flag is used, `type' displays all of the places that contain

    an executable named `file'.  This includes aliases, builtins, and

    functions, if and only if the -p flag is not also used.
    The -f flag suppresses shell function lookup.
    The -P flag forces a PATH search for each NAME, even if it is an alias,

    builtin, or function, and returns the name of the disk file that would

    be executed.

typeset: typeset [-afFirtx] [-p] name[=value] ...

     Obsolete.  See `declare'.
$ help command

command: command [-pVv] command [arg ...]

     Runs COMMAND with ARGS ignoring shell functions.  If you have a shell

    function called `ls', and you wish to call the command `ls', you can

    say "command ls".  If the -p option is given, a default value is used

    for PATH that is guaranteed to find all of the standard utilities.  If

    the -V or -v option is given, a string is printed describing COMMAND.

    The -V option produces a more verbose description.
$ help builtin

builtin: builtin [shell-builtin [arg ...]]

     Run a shell builtin.  This is useful when you wish to rename a

    shell builtin to be a function, but need the functionality of the

    builtin within the function itself.
$ help function

function: function NAME { COMMANDS ; } or NAME () { COMMANDS ; }

     Create a simple command invoked by NAME which runs COMMANDS.

    Arguments on the command line along with NAME are passed to the

    function as $0 .. $n.
$ help local

local: local name[=value] ...

     Create a local variable called NAME, and give it VALUE.  LOCAL

    can only be used within a function; it makes the variable NAME

    have a visible scope restricted to that function and its children.
$ help declare

declare: declare [-afFirtx] [-p] [name[=value] ...]

     Declare variables and/or give them attributes.  If no NAMEs are

    given, then display the values of variables instead.  The -p option

    will display the attributes and values of each NAME.
    The flags are:
      -a        to make NAMEs arrays (if supported)

      -f        to select from among function names only

      -F        to display function names (and line number and source file name if

        debugging) without definitions

      -i        to make NAMEs have the `integer' attribute

      -r        to make NAMEs readonly

      -t        to make NAMEs have the `trace' attribute

      -x        to make NAMEs export
    Variables with the integer attribute have arithmetic evaluation (see

    `let') done when the variable is assigned to.
    When displaying values of variables, -f displays a function's name

    and definition.  The -F option restricts the display to function

    name only.
    Using `+' instead of `-' turns off the given attribute instead.  When

    used in a function, makes NAMEs local, as with the `local' command.
$