Question

Bash文档说echo写入stdout。我有一个脚本，将stderr重定向到带有2>/home/pi/mydir/stderr-log.txt的文件。它不会重定向stdout。 echo输出的文本仍将进入日志文件。

通过在命令末尾添加&可以在后台运行脚本有什么不同吗？

完整的脚本：

#! /bin/sh

case "$1" in 
start)
echo "Starting mjpg_streamer!"
#First init
/usr/local/bin/mjpg_streamer -i "/usr/local/lib/mjpg-streamer/input_uvc.so -n -f 30 -r 640x480 -d /dev/video0" -o "/usr/local/lib/mjpg-streamer/output_http.so -p 8085 -w /usr/local/share/mjpg-streamer/www" 2>/home/pi/mydir/stderr-log.txt &
#Second init
/usr/local/bin/mjpg_streamer -i "/usr/local/lib/mjpg-streamer/input_uvc.so -n -f 30 -r 640x480 -d /dev/video1" -o "/usr/local/lib/mjpg-streamer/output_http.so -p 8086 -w /usr/local/share/mjpg-streamer/www" 2>/home/pi/mydir/stderr-log.txt &
;;
stop)
echo "Stopping mjpg_streamer!"
killall mjpg_streamer
;;
*)
echo "usage: videoinit {start|stop}"
exit 1
;;
esac
exit 0

调用该脚本的脚本（当它在日志文件中找到新的错误消息时）：

#!/bin/bash

    ERRORLOG="/home/pi/mydir/stderr-log.txt"
    LINECOUNT=0
    NEWLINECOUNT=0
    rm ${ERRORLOG}
    touch ${ERRORLOG}
    while true; do
       inotifywait -q -e modify ${ERRORLOG} > /dev/null
       NEWLINECOUNT=$(grep --count "Error grabbing frames" ${ERRORLOG} )
       if [[ NEWLINECOUNT > LINECOUNT ]]; then
          LINECOUNT=NEWLINECOUNT
          /etc/init.d/videoinit stop
          echo "Attempting mjpg-streamer reboot."
          /etc/init.d/videoinit start
       fi
    done

bash stdout输出出现在重定向的stderr文件中

0 个答案: