没有cd命令的手册页

Ubuntu的Linux 15.10 – 我只是注意到,没有手册页的cd

这似乎有点奇怪。

我试过了:

 man cd 

在CMD线,我回来了

 No manual entry for cd 

我正在试图find文件

 cd - 

在最后一个目录和当前目录之间翻转是非常方便的

cd --

这似乎是一个别名

 cd ~ 

我在这里错过了非常明显的东西,还是应该在手册页面?

cd不是一个命令,它是内置到你的shell。 这是必要的,因为您当前的工作目录是由PWD (打印工作目录)环境变量控制的。

父进程的环境变量不能被子进程改变。 所以,如果你的shell运行了/bin/cd ,它改变了PWD它只会影响/bin/cd和它运行的任何东西。 它不会改变外壳的PWD

一些系统,如OS X,将cd man页面映射到builtin列表中,其中列出了所有builtin的shell,并让你知道你应该看看你的shell的手册页。

你可以用echo $SHELL来检查你的shell,可能是bash

cd是一个内置shell命令。

你可以在Bash上用cd打开一个帮助页面

 $ help cd 

目前显示(Ubuntu 16.04):

 $ help cd cd: cd [-L|[-P [-e]] [-@]] [dir] Change the shell working directory. Change the current directory to DIR. The default DIR is the value of the HOME shell variable. The variable CDPATH defines the search path for the directory containing DIR. Alternative directory names in CDPATH are separated by a colon (:). A null directory name is the same as the current directory. If DIR begins with a slash (/), then CDPATH is not used. If the directory is not found, and the shell option `cdable_vars' is set, the word is assumed to be a variable name. If that variable has a value, its value is used for DIR. Options: -L force symbolic links to be followed: resolve symbolic links in DIR after processing instances of `..' -P use the physical directory structure without following symbolic links: resolve symbolic links in DIR before processing instances of `..' -e if the -P option is supplied, and the current working directory cannot be determined successfully, exit with a non-zero status -@ on systems that support it, present a file with extended attributes as a directory containing the file attributes The default is to follow symbolic links, as if `-L' were specified. `..' is processed by removing the immediately previous pathname component back to a slash or the beginning of DIR. Exit Status: Returns 0 if the directory is changed, and if $PWD is set successfully when -P is used; non-zero otherwise. 

不幸的是,它不能回答你的问题。 有文件,但是。

你可以去

 $ man builtins 

它用less默认查看器打开许多页面。 我可以通过按/键找到cd的帮助,然后输入cd ,然后Enter ,然后按两次让我到达子字符串的第三个实例,帮助,其中:

  cd [-L|[-P [-e]] [-@]] [dir] Change the current directory to dir. if dir is not supplied, the value of the HOME shell variable is the default. Any addi‐ tional arguments following dir are ignored. The variable CDPATH defines the search path for the directory containing dir: each directory name in CDPATH is searched for dir. Alternative directory names in CDPATH are separated by a colon (:). A null directory name in CDPATH is the same as the current directory, ie, ``.''. If dir begins with a slash (/), then CDPATH is not used. The -P option causes cd to use the physical directory structure by resolving symbolic links while traversing dir and before processing instances of .. in dir (see also the -P option to the set builtin command); the -L option forces symbolic links to be followed by resolving the link after processing instances of .. in dir. If .. appears in dir, it is processed by removing the immediately previous pathname component from dir, back to a slash or the beginning of dir. If the -e option is supplied with -P, and the current working directory cannot be success‐ fully determined after a successful directory change, cd will return an unsuccessful status. On systems that support it, the -@ option presents the extended attributes associated with a file as a directory. An argument of - is converted to $OLDPWD before the directory change is attempted. If a non-empty direc‐ tory name from CDPATH is used, or if - is the first argument, and the directory change is successful, the absolute pathname of the new working directory is written to the standard output. The return value is true if the directory was successfully changed; false otherwise. 

从最后看第七行。

请注意,没有参数 – 这似乎意味着它实际上忽略了它。

相关摘录从bash man page覆盖cd -使用cd -

  cd [-L|[-P [-e]] [-@]] [dir] Change the current directory to dir. ... An argument of - is converted to $OLDPWD before the directory change is attempted. If a non- empty directory name from CDPATH is used, or if - is the first argument, and the directory change is successful, the absolute pathname of the new working directory is written to the standard output. The return value is true if the directory was successfully changed; false otherwise.