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获取有关 Linux shell 内置命令的帮助( 二 )

Linux Shell

从上面的清单中可以看出，help 命令本身就是内置的 。
你可以通过向 help 命令提供你感兴趣的内置命令名称来获取关于它们的更多信息，例如 help dirs：
$ help dirsdirs: dirs [-clpv] [+N] [-N] Display directory stack. Display the list of currently remembered directories. Directories find their way onto the list with the `pushd' command; you can get back up through the list with the `popd' command. Options: -c clear the directory stack by deleting all of the elements -l do not print tilde-prefixed versions of directories relative to your home directory -p print the directory stack with one entry per line -v print the directory stack with one entry per line prefixed with its position in the stack Arguments: +N Displays the Nth entry counting from the left of the list shown by dirs when invoked without options, starting with zero. -N Displays the Nth entry counting from the right of the list shown by dirs when invoked without options, starting with zero. Exit Status: Returns success unless an invalid option is supplied or an error occurs.内置命令提供了每个 shell 的大部分功能 。你使用的任何 shell 都有一些内置命令，但是如何获取这些内置命令的信息可能因 shell 而异 。例如，对于 zsh，你可以使用 man zshbuiltins 命令获得其内置命令的描述 。
$ man zshbuiltinsZSHBUILTINS(1) General Commands Manual ZSHBUILTINS(1)NAME zshbuiltins - zsh built-in commandsSHELL BUILTIN COMMANDS Some shell builtin commands take options as described in individual en‐ tries; these are often referred to in the list below as `flags' to avoid confusion with shell options, which may also have an effect on the behav‐ iour of builtin commands. In this introductory section, `option' always has the meaning of an option to a command that should be familiar to most command line users.…在这个冗长的手册页中，你将找到一个内置命令列表，其中包含有用的描述，如下摘录中所示：
bg [ job ... ]job ... & Put each specified job in the background, or the current job if none is specified.bindkey See the section `Zle Builtins' in zshzle(1).break [ n ] Exit from an enclosing for, while, until, select or repeat loop. If an arithmetic expression n is specified, then break n levels instead of just one.最后Linux 内置命令对于每个 shell 都很重要，它的操作类似特定于 shell 的命令一样 。如果你经常使用不同的 shell，并注意到你经常使用的某些命令似乎不存在或者不能按预期工作，那么它可能是你使用的其他 shell 之一中的内置命令 。


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