Ubuntu中update-alternatives命令（版本切换）_update-alternatives --install /usr/bin/g++ g++ /us

1、update-alternatives 命令选项介绍：display、install、remove、config

---

2、display命令：（查看命令链接信息）

# update-alternatives --display name（命令名称）

$ update-alternatives --display gcc
gcc - auto mode
  link currently points to /usr/bin/gcc-4.7
/usr/bin/gcc-4.7 - priority 100
/usr/bin/gcc-4.8 - priority 50
Current 'best' version is '/usr/bin/gcc-4.7'.
1
2
3
4
5
6
7
8

---

3、install命令：（增加命令链接）

# update-alternatives --install link name path priority
# link -> 链接原目录 name -> 链接符名称 
# path -> 链接新目录 priority -> 优先级

$ sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.7 100
$ sudo update-alternatives --install /usr/bin/g++ g++ /usr/bin/g++-4.8 50

$ update-alternatives --display gcc
gcc - auto mode
  link currently points to /usr/bin/gcc-4.7
/usr/bin/gcc-4.7 - priority 100
/usr/bin/gcc-4.8 - priority 50
Current 'best' version is '/usr/bin/gcc-4.7'.
1
2
3
4
5
6
7
8
9
10
11
12
13

---

4、remove命令：（删除命令链接）

# update-alternatives --remove name path
# name, path 与 install命令一样

$ sudo update-alternatives --remove g++ /usr/bin/g++-4.8

$ update-alternatives --display gcc
gcc - auto mode
  link currently points to /usr/bin/gcc-4.7
/usr/bin/gcc-4.7 - priority 100
Current 'best' version is '/usr/bin/gcc-4.7'.
1
2
3
4
5
6
7
8
9
10

---

5、config命令：（配置命令链接）

# update-alternatives --config name

$ update-alternatives --config gcc
There are 2 choices for the alternative gcc (providing /usr/bin/gcc).

  Selection    Path              Priority   Status
------------------------------------------------------------
* 0            /usr/bin/gcc-4.7   100       auto mode
  1            /usr/bin/gcc-4.7   100       manual mode
  2            /usr/bin/gcc-4.8   50        manual mode

Press enter to keep the current choice[*], or type selection number: 
1
2
3
4
5
6
7
8
9
10
11
12

---

6、auto和manual模式转换
默认为auto模式，将manual模式改为auto模式：

# update-alternatives --auto name
$ update-alternatives --auto gcc
1
2

---