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Yves
Asked: 2018-08-08 17:12:52 +0800 CST

为什么我不能哪个 pushd

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pushd在编写 bash 脚本时，我已经使用popd了很长时间。但是今天当我执行时which pushd，我没有得到任何输出。我完全无法理解这一点。我一直认为这pushd只是一个命令，就像cd，ls等等。

那为什么which pushd什么都不给我？

which pushd

1 个回答

  1. Best Answer

    popd并且pushd是内置在 Bash 中的命令，它们不是作为真正的二进制文件存在于 HDD 上的实际可执行文件。

    摘录 bash 手册页 
       DIRSTACK
          An array variable (see Arrays below) containing the current 
          contents of the directory stack.  Directories appear in the stack 
          in the order they are displayed by the dirs builtin.  Assigning to 
          members of  this  array variable may be used to modify directories 
          already in the stack, but the pushd and popd builtins must be used 
          to add and remove directories.  Assignment to this variable will 
          not change the current directory.  If DIRSTACK is unset, it loses 
          its special properties, even if it is subsequently reset.

    所有内置命令的完整列表可在 Bash 手册页以及此处 - http://structure.usc.edu/bash/bashref_4.html中找到。

    您还可以使用compgen -b或enable获取所有这些内置函数的完整列表：

    补偿 
    $ compgen -b | grep -E "^push|^pop"
popd
pushd
    使能够 
    $ enable -a | grep -E "\bpop|\bpus"
enable popd
enable pushd

    此外，如果您想获得有关内置函数的帮助，可以使用以下help命令：

    $ help popd | head -5
popd: popd [-n] [+N | -N]
    Remove directories from stack.

    Removes entries from the directory stack.  With no arguments, removes
    the top directory from the stack, and changes to the new top directory.

$ help pushd | head -5
pushd: pushd [-n] [+N | -N | dir]
    Add directories to stack.

    Adds a directory to the top of the directory stack, or rotates
    the stack, making the new top of the stack the current working
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