#Bash 的 hash 命令

hash [OPTION]... [NAME]...

功能

记录或打印程序位置，执行被记录的命令时不再进行查找。

Bash 在默认配置下，执行一次命令后会自动进行记录。

类型

Bash 内置命令。

参数

OPTION - 选项：
- -d - 移除 NAME 的记录
- -l - 以命令行的格式打印记录列表
- -p pathname - 使用 PATHNAME 作为 NAME 的完整路径
- -r - 移除所有记录
- -t - 查看记录
NAME - 要查看或记录的命令列表

#示例

查看记录

$ hash -l           # 列出记录
builtin hash -p /usr/bin/cp cp
builtin hash -p /bin/ls ls
builtin hash -p /usr/bin/cat cat
$ hash -t ls        # 查看 ls 的路径
/bin/ls

添加记录

$ type arch                         # 查看命令的类型，返回命令的路径
arch is /usr/bin/arch
$ hash arch                         # 记录位置
$ type arch                         # 再次查看命令的类型，显示命令被哈希缓存，不再从 PATH 中进行查找
arch is hashed (/usr/bin/arch)

指定记录

$ hash -p /path/to/my_cmd my_cmd
$ type my_cmd
my_cmd is hashed (/path/to/my_cmd)

移除记录

$ hash -d my_cmd
$ type my_cmd
-bash: type: my_cmd: not found

#手册

hash: hash [-lr] [-p pathname] [-dt] [name ...]
    Remember or display program locations.

    Determine and remember the full pathname of each command NAME.  If
    no arguments are given, information about remembered commands is displayed.

    Options:
      -d	forget the remembered location of each NAME
      -l	display in a format that may be reused as input
      -p pathname	use PATHNAME as the full pathname of NAME
      -r	forget all remembered locations
      -t	print the remembered location of each NAME, preceding
    		each location with the corresponding NAME if multiple
    		NAMEs are given
    Arguments:
      NAME	Each NAME is searched for in $PATH and added to the list
    		of remembered commands.

    Exit Status:
    Returns success unless NAME is not found or an invalid option is given.