bash 插入 HDMI 时自动检测
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Automatically detect when HDMI is plugged in
提问by Katembers
Sometimes I connect my laptop to my TV over HDMI to have a bigger screen. Unfortunately, it doesn't automatically switch the audio output, so I have to do that myself every single time I plug or unplug it, with either of those two, to have the sound come from where I want it to come from.
有时我通过 HDMI 将笔记本电脑连接到电视以获得更大的屏幕。不幸的是，它不会自动切换音频输出，所以我每次插入或拔出它时都必须自己这样做，使用这两者中的任何一个，以使声音来自我想要的地方。
pacmd set-card-profile 0 output:hdmi-stereo-extra1pacmd set-card-profile 0 output:analog-stereo+input:analog-stereo
pacmd set-card-profile 0 output:hdmi-stereo-extra1pacmd set-card-profile 0 output:analog-stereo+input:analog-stereo
Is there any way to detect if HDMI is plugged in, or at least if a change has occurred? Thanks!
有没有办法检测HDMI是否插入，或者至少是否发生了变化？谢谢！
Linux Mint 18.2 Xfce x64, Asus P756U
Linux Mint 18.2 Xfce x64，华硕 P756U
回答by George Vasiliou
I am using two different ways to determine if HDMI is plugged in:
我使用两种不同的方法来确定是否插入了 HDMI：
a) Using xrandr
A simple xrandr will report your hdmi monitor as connected
To use this in a script you can do something like:
a) 使用 xrandr
一个简单的 xrandr 会将您的 hdmi 显示器报告为已连接要在脚本中使用它，您可以执行以下操作：
hdmi_active=$(xrandr |grep ' connected' |grep 'HDMI' |awk '{print }')
Above will return the connected hdmi port (i.e HDMI-1) or will return nothing if no HDMI is connected.
以上将返回已连接的 hdmi 端口（即 HDMI-1），如果未连接 HDMI，则不返回任何内容。
You can then use something like
然后你可以使用类似的东西
[[ ! -z "$hdmi_active" ]] && do_your_stuff
zbecomes trueif $hdmi_activeis not set . ! zreverts this behavior and returns trueif hdmi_active has a value = hdmi is connected
z变为trueif$hdmi_active未设置。如果 hdmi_active 具有值 = hdmi 已连接，则! z恢复此行为并返回true
b) Using the HDMI status file:
b) 使用 HDMI 状态文件：
$ cat /sys/class/drm/card0/*HDMI*/status
This returns connected / disconnected for your hdmi ports:
这将为您的 hdmi 端口返回连接/断开连接：
$ cat /sys/class/drm/card0/*HDMI*/status
disconnected
disconnected
You can then test against that result with something like:
然后，您可以使用以下内容对该结果进行测试：
hdmi_active="$(cat /sys/class/drm/card0/*HDMI*/status |grep '^connected')" #Using ^ we avoind matching disconnected from the regex match, since ^ in an anchor to the beginning of the line
[[ ! -z "$hdmi_active" ]] && do_your_stuff #hdmi is active
