Bash中的内置命令非常有用，但是“内置”本身实际上做什么呢？今天的超级用户问答帖子回答了一位好奇的读者的问题。

今天的问答环节是由SuperUser提供的，SuperUser是Stack Exchange的一个分支，是一个由社区驱动的问答网站分组。

问题

超级用户读者lfalin想知道Bash中的内置命令的作用：

I know what a builtin command is, but what does builtin itself do? Executing which ls shows me /bin/ls, but executing which builtin returns nothing. man builtin just gives me a list of builtin commands, one of which is builtin. The rest of the man page explains what a builtin command is, but not what builtin itself is. builtin –help tells me builtin: usage: builtin [shell-builtin [arg …]], but still not what it does. Is it a part of Bash in a way that other builtin commands are not?

Bash中的内置命令是做什么的？

答案

超级用户贡献者斯皮夫为我们提供了答案：

The builtin command makes sure you run the shell built-in version of the command rather than running another command with the same name.

For example, imagine you defined a shell function named cd to print some extra status every time you change directories, but you messed it up and now you cannot change directories correctly. So now you can type builtin cd ~ to successfully cd back to your home directory without running your broken shell function.

By the way, my copy of the Bash man page has a section called “SHELL BUILTIN COMMANDS”, and it defines the meaning of the builtin command in that section (transcribed below).

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