Run command every second in Bash?

Question

I want to write some image downloader and assign it on bash. What I have and what I need:

I have:

1. Command, which works fine (something like wget http://mywebcam.com/image.jpg -O /var/cam/Image.jpg)

2. Root rights

3. Fast Internet line between my server and my webcam

What I need:

Download image from camera every second*(sleep 1?)* and rewrite it localy (my command do it well) Run this script at once and don't worry about restart (I think I need to create file with bash commands and run it once + set crontab work "on reboot" to this file, right?)

Maybe there's someone who knows what should I to do?

Answer 1

If you want to run a command at one second intervals (one second between the end of one command and the beginning of the next, which is not the same as running every second), just do:

while sleep 1; do cmd; done 

If you want that to start on reboot, the method will depend on your system.

Note that it is certainly possible to start an execution every second rather than running at one second intervals, but I suspect that is not actually what you want. In addition, there are inherent risks with doing so. For example, if the system gets sluggish and the command starts taking longer than one second to run you may run out of resources.

Answer 2

The command watch will do this for you straight up. It also displays the result in a nice way.

$ watch -n 1 date 

Substitute date for your command. The -n option specifies the interval in seconds.