时间限制视频录制：
screenrecord --time-limit 20 /sdcard/demo.mp4
抓屏：
screencap -p /sdcard/screen.png
screenshot /sdcard/screen.png
视频录制命令screenrecord
# screenrecord --help
Usage: screenrecord [options] <filename>
Records the device‘s display to a .mp4 file.
Options:
--size WIDTHxHEIGHT
Set the video size, e.g. "1280x720". Default is the device‘s main
display resolution (if supported), 1280x720 if not. For best results,
use a size supported by the AVC encoder.
--bit-rate RATE
Set the video bit rate, in megabits per second. Default 4Mbps.
--time-limit TIME
Set the maximum recording time, in seconds. Default / maximum is 180.
--rotate
Rotate the output 90 degrees.
--verbose
Display interesting information on stdout.
--help
Show this message.
截图命令screencap
# screencap -h
usage: screencap [-hp] [-d display-id] [FILENAME]
-h: this message
-p: save the file as a png.
-d: specify the display id to capture, default 0.
# screenshot -h
screenshot: invalid option -- h
usage: screenshot [-s soundfile] filename.png
-s: play a sound effect to signal success
-i: autoincrement to avoid overwriting filename.png