PATH环境变量也有缓存

PATH环境变量也有缓存

 

hash - hash database access method

hase 命令：用来显示和清除哈希表，执行命令的时候，系统将先查询哈希表。

当你输入命令，首先在hash表中寻找，如果不存在，才会利用$PATH环境变量指定的路径寻找命令，然后加以执行。同时也会将其放入到hash table 中，当下一次执行同样的命令时就不会再通过$PATH寻找。以此提高命令的执行效率。

显示哈希表中命令使用频率

$ hash

hits command

   6 /usr/bin/svn

   1 /bin/chown

   3 /bin/bash

   4 /usr/bin/git

  12 /usr/bin/php

   1 /bin/rm

   1 /bin/chmod

   1 /usr/bin/nmap

   5 /bin/cat

  13 /usr/bin/vim

   3 /usr/bin/sudo

   4 /bin/sed

   2 /bin/ps

   2 /usr/bin/man

  23 /bin/ls

 

显示哈希表

$ hash -l

builtin hash -p /usr/bin/svn svn

builtin hash -p /bin/chown chown

builtin hash -p /bin/bash bash

builtin hash -p /usr/bin/git git

builtin hash -p /usr/bin/php php

builtin hash -p /bin/rm rm

builtin hash -p /bin/chmod chmod

builtin hash -p /usr/bin/nmap nmap

builtin hash -p /bin/cat cat

builtin hash -p /usr/bin/vim vim

builtin hash -p /usr/bin/sudo sudo

builtin hash -p /bin/sed sed

builtin hash -p /bin/ps ps

builtin hash -p /usr/bin/man man

builtin hash -p /bin/ls ls

 

显示命令的完整路径

$ hash -t git

/usr/bin/git

 

向哈希表中增加内容

 

$ hash -p /home/www/deployment/run run

 

$ run

Usage: /home/www/deployment/run [OPTION] <server-id> <directory/timepoint>

 

OPTION:

development <domain> <host>

testing <domain> <host>

production <domain> <host>

 

branch {development|testing|production} <domain> <host> <branchname>

revert {development|testing|production} <domain> <host> <revision>

backup <domain> <host> <directory>

release <domain> <host> <tags> <message>

 

list

list <domain> <host>

 

clean {development|testing|production} <domain> <host>

log <project> <line>

 

conf list

cron show

cron setup

cron edit

 

 

命令等同于

PATH=$PATH:$HOME/www/deployment

 

export PATH

 

删除哈希表内容

$ hash -r

 

$ hash -l

hash: hash table empty