watch Command

While researching some issues I'm having with iostat, I found an interesting command called 'watch'

Instead of running the usual command (up arrow, return, up arrow, return)

[root@nms-tpt-1 ~]# cat /proc/diskstats | grep "sda "
   8    0 sda 42113 18004 1395004 80723 18000492 45624354 508998694 7650613 0 4953776 7730941
[root@nms-tpt-1 ~]# cat /proc/diskstats | grep "sda "
   8    0 sda 42113 18004 1395004 80723 18000492 45624354 508998694 7650613 0 4953776 7730941
[root@nms-tpt-1 ~]# cat /proc/diskstats | grep "sda "
   8    0 sda 42113 18004 1395004 80723 18000497 45624372 508998878 7650614 0 4953777 7730942

...or writing a never ending while loop. You can issue "watch" which will run your program (clearing the screen each time) and even show you (highlighted) the diffs between each call ... pretty nice:

[root@nms-tpt-1 ~]# watch -n 1 -d 'cat /proc/diskstats | grep "sda "'

would show in a new screen:

Every 1.0s: cat /proc/diskstats | grep "sda "                                                                                                            Mon Dec  7 09:42:18 2009

   8    0 sda 42113 18004 1395004 80723 18000540 45624456 508999894 7650638 0 4953787 7730966

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