Watch is a very useful command for periodically running another command - in this using mysqladmin to display the processlist. This is useful for monitoring which queries are causing your server to clog up. More info here: http://codeinthehole.com/archives/2-Monitoring-MySQL-processes.html

This command displays a clock on your terminal which updates the time every second. Press Ctrl-C to exit. A couple of variants: A little bit bigger text: watch -t -n1 "date +%T|figlet -f big" You can try other figlet fonts, too. Big sideways characters: watch -n 1 -t '/usr/games/banner -w 30 $(date +%M:%S)' This requires a particular version of banner and a 40-line terminal or you can adjust the width ("30" here). Show Sample Output

Create a binary clock. Show Sample Output

It's not my code, but I found it useful to know how many open connections per request I have on a machine to debug connections without opening another http connection for it. You can also decide to sort things out differently then the way it appears in here. Show Sample Output

Other logs can be monitored similarly, e.g. watch "tail -15 /var/log/daemon.log"

Short method of "while x=0; do foo ; sleep 1 ; done"

use "watch" instead of while-loops in these simple cases

This command repeatedly gets the specified process' stack using pstack (which is an insanely clever and tiny wrapper for gdb) and displays it fullscreen. Since it updates every second, you rapidly get an idea of where your program is stuck or spending time. The 'tac' is used to make the output grow down, which makes it less jumpy. If the output is too big for your screen, you can always leave the 'tac' off to see the inner calls. (Or, better yet--get a bigger screen.) Caveats: Won't work with stripped binaries and probably not well with threads, but you don't want to strip your binaries or use threads anyway. Show Sample Output

This will allow you to watch as matches occur in real-time. To filter out only ACCEPT, DROP, LOG..etc, then run the following command: watch 'iptables -nvL | grep -v "0 0" && grep "ACCEPT"' The -v is used to do an inverted filter. ie. NOT "0 0"

I wanted to create a copy of my whole laptop disk on an lvm disk of the same size. First I created the logical volume: lvcreate -L120G -nlaptop mylvms SOURCE: dd if=/dev/sda bs=16065b | netcat ip-target 1234 TARGET: nc -l -p 1234 | dd of=/dev/mapper/mylvms-laptop bs=16065b to follow its process you issue the following command in a different terminal STATS: on target in a different terminal: watch -n60 -- kill -USR1 $(pgrep dd) (see http://www.commandlinefu.com/commands/view/4356/output-stats-from-a-running-dd-command-to-see-its-progress)

Show active calls as the happen on an Asterisk server. Note that the Asterisk command (in single quotes) is formatted for Asterisk 1.6. Use the -n flag on the watch command to modify the refresh period (in seconds - default is 2 seconds). Show Sample Output

Shows updated status in a terminal window for connections to port '80' in a human-friendly form. Use 'watch -n1' to update every second, and 'watch -d' to highlight changes between updates. If you wish for status updates on a port other than '80', always remember to put a space afterwards so that ":80" will not match ":8080". Show Sample Output

If your web server is down, this command will periodically attempt to connect to it. If the output is blank, your server is not yet up. If you see HTML, your server is up. Obviously, you need to replace the Google URL with your web server URL... * 'watch' -- a command for re-executing a command and displaying the output * '-n 15' -- tells watch to redo the command every 15 seconds * 'curl' -- a handy utility for getting the source of a web page * '-s' -- tells curl to be silent about failing * '--connect-timeout 10' -- Try to connect for 10 seconds

to omit "grep -v", put some brackets around a single character

Binary clock with separate H:M:S. Show Sample Output

http://alvinalexander.com/linux/unix-linux-process-memory-sort-ps-command-cpu for an overview of --sort available values

While copying a large file that may take up a good chunk of your hard drive, start the copy and run this command concurrently. It will print out the disk information every second. It's pretty handy when you have a large copy with nothing to monitor the progress.

Shows all those processes; useful when building some massively forking script that could lead to zombies when you don't have your waitpid()'s done just right.

Shows a simple clock in the console -t param removes the watch header Ctrl-c to exit Show Sample Output

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