~/.config/karabiner/assets/complex_modification/switch_im.json

switch_im.json

{
  "title": "Switch IM",
  "rules": [
    {
      "description": "right_control -> CN",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "right_control"
          },
          "to": [{
            "shell_command": "/usr/local/bin/InputSourceSelector select 'com.baidu.inputmethod.BaiduIM.pinyin'"
          }]
        }
      ]
    },
    {
      "description": "right_shift -> US",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "right_shift"
          },
          "to": [{
            "shell_command": "/usr/local/bin/InputSourceSelector select 'com.apple.keylayout.US'"
          }]
        }
      ]
    },
    {
      "description": "right_alt -> JP",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "right_alt"
          },
          "to": [{
            "shell_command": "/usr/local/bin/InputSourceSelector select 'com.justsystems.inputmethod.atok30.Japanese'"
          }]
        }
      ]
    }
  ]
}