How do I monitor Linux/BSD system over time without scrolling output?

Posted by Vivek Gite [Last updated: March 27, 2006]

Suppose you would like to monitor memory utilization over time without having to look at scrolling output or disk space without scrolling output then normal commands do not provide any options.

You need to use watch command, which execute a program periodically, showing output in fullscreen mode. It runs command repeatedly, displaying its output. This allows you to watch the program output change over time. By default, the program is run every 2 seconds.

To watch memory usage:

$ watch free -m

Run free –m program is run every 5 seconds:

$ watch -n 5 free -m

To watch disk space usage:

$ watch df -h

To watch the contents of a directory change, you could use:

$ watch -d ls –l

Options:

The -d flag will highlight the differences between successive updates.
The –n {SECOND} flag use to specify a different interval.

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Discussion on This Article:

Anonymous Says: September 22nd, 2006 at 7:48 pm
that doesnt work in bsd. im searching for the solution right now, just letting you know that watch in open and freebsd does something else than it does in linux
John Says: February 27th, 2007 at 6:35 am
For FreeBSD:

cd /usr/ports/sysutils/cmdwatch && make install clean

then substitute cmdwatch for watch as listed above.

The other BSD’s should be very similar.
The stock BSD watch is for snooping on other tty’s (which can be rather useful too ).

But thx for this, it’s helpful to keep an eye on httpd errors, during web development, as well as busloads of other tasks.