如何将stderr重定向到文件，并将某些回显（不是stdout）重定向到同一文件

Question

I am learning bash scripting. I am trying to write a simple script that runs apt-get update in regular intervals using crontab for scheduling. I am trying to send the errors (with the time the error occurred )to a log file but I am only getting the error and not the time,

The script file ,

echo "----------   $(date +"%d %B %G") , $(date +%r) :";
apt-get update;

The crontab file (sudo crontab -e)

0 */5 * * * /root/scripts/update_sys.sh 2>/root/logs/updateLog 1>/dev/null

as far as I understood the echo statement in the script file dumps the text to the standard output, thus it ends up in /dev/null , but how could I include it in the log file without the entire info ( I mean info that apt-get dumps like Hit http://in.archive.ubuntu.com precise-backports/main Sources ) ?

Answer 1

If you can modify the script but not the crontab then the simplest is to redirect the echoes in the script to stderr .

echo "----------   $(date +"%d %B %G") , $(date +%r) :" >&2

All stdout will still go to /dev/null and all stderr will be logged along with the echoes to stderr .

If you can modify the crontab but not the script, then the simplest would be devnull 's suggestion.

If you can modify either, then you have a choice.