使用crontab＆nohup将输出重定向到具有日期格式名称的文件

Question

Now I have a script start.sh to start my application:

java -Dlog4j.configuration=file:~/log4j.xml -Xmx2048m -jar ~/myapp.jar

And I add this script to crontab to make it as a schedule job:

15 05 * * 1-5 /home/me/start.sh >> /home/me/cronlog/$(date +"\%F")-start.log 2>&1

which redirects the output of start.sh to a separate file with date format name

Right now, I'd like use nohup and put the redirect command to the start.sh script rather than in crontab

So the crontab looks clean:

15 05 * * 1-5 /home/me/start.sh

And in the start.sh , after testing it should be:

nohup java -Dlog4j.configuration=file:~/log4j.xml -Xmx2048m -jar ~/myapp.jar > ~/cronlog/$(date +"%F")-nohup.log 2>&1 &

Here is my question:

1. Why in crontab , backslash \\ is needed but in the new start.sh script, it isn't needed?

2. I'd like to record every output to the file including exception or error, should it ends with up 2>&1 & . The last & is from nohup . So what exactly do the 2>&1 and '&` mean?

Answer 1

2>&1 means "redirect standard error on standard output"

http://www.tldp.org/LDP/abs/html/io-redirection.html

As you can see in that page, the numebers refer to the file descriptors used by the OS to point the resources (stderr, stdout), and &> is a redirection operator.