Commands using tail

Netcat is used to serve a log-file over a network on port 1234.

Point a browser to the specified server/port combo to view log-file updates in real-time.

Debian-specific but very useful as cron files are prone to very subtle gotchas

Just a quick hack to give reasonable filenames to TrueType and OpenType fonts.

I'd accumulated a big bunch of bizarrely and inconsistently named font files in my ~/.fonts directory. I wanted to copy some, but not all, of them over to my new machine, but I had no idea what many of them were. This script renames .ttf files based on the name embedded inside the font. It will also work for .otf files, but make sure you change the mv part so it gives them the proper extension.

REQUIREMENTS: Bash (for extended pattern globbing), showttf (Debian has it in the fontforge-extras package), GNU grep (for context), and rev (because it's hilarious).

BUGS: Well, like I said, this is a quick hack. It grew piece by piece on the command line. I only needed to do this once and spent hardly any time on it, so it's a bit goofy. For example, I find 'rev | cut -f1 | rev' pleasantly amusing --- it seems so clearly wrong, and yet it works to print the last argument. I think flexibility in expressiveness like this is part of the beauty of Unix shell scripting. One-off tasks can be be written quickly, built-up as a person is "thinking aloud" at the command line. That's why Unix is such a huge boost to productivity: it allows each person to think their own way instead of enforcing some "right way".

On a tangent: One of the things I wish commandlinefu would show is the command line HISTORY of the person as they developed the script. I think it's that conversation between programmer and computer, as the pipeline is built piece-by-piece, that is the more valuable lesson than any canned script.

Another way of counting the line output of tail over 10s not requiring pv.

Cut to have the average per second rate :

tail -n0 -f access.log>/tmp/tmp.log & sleep 10; kill $! ; wc -l /tmp/tmp.log | cut -c-2

You can also enclose it in a loop and send stderr to /dev/null :

while true; do tail -n0 -f access.log>/tmp/tmp.log & sleep 2; kill $! ; wc -l /tmp/tmp.log | cut -c-2; done 2>/dev/null

Displays the realtime line output rate of a logfile.

-l tels pv to count lines

-i to refresh every 10 seconds

-l option is not in old versions of pv. If the remote system has an old pv version:

ssh tail -f /var/log/apache2/access.log | pv -l -i10 -r >/dev/null

Change the cut range for hits per 10 sec, minute and so on... Grep can be used to filter on url or source IP.

This searches the Apache error_log for each of the 5 most significant Apache error levels, if any are found the date is then cut from the output in order to sort then print the most common occurrence of each error.

gentoo only or gentoo-like linux distributions.

Several people have submitted commands to do this, but I think this is the simplest solution. It also happens to be the most portable one: It should work with any sh or csh derived shell under any UNIX-like OS.

Oh by the way, with my German locale ($LC_TIME set appropriately) it prints "g" most of the time, and sometimes (on Wednesdays) it prints "h". It never prints "y".

Change open-command and type to suit your needs. One example would be to open the last .jpg file with Eye Of Gnome:

eog $(ls -rt *.jpg | tail -n 1)

Prints the top 10 memory consuming processes (with children and instances aggregated) sorted by total RSS and calculates the percentage of total RAM each uses. Please note that since RSS can include shared libraries it is possible for the percentages to add up to more that the total amount of RAM, but this still gives you a pretty good idea. Also note that this does not work with the mawk version of awk, but it works fine with GNU Awk which is on most Linux systems. It also does not work on OS X.

Finds all C++, Python, SWIG files in your present directory (uses "*" rather than "." to exclude invisibles) and counts how many lines are in them. Returns only the last line (the total).

This command loops over all of the processes in a system and creates an associative array in awk with the process name as the key and the sum of the RSS as the value. The associative array has the effect of summing a parent process and all of it's children. It then prints the top ten processes sorted by size.

Change the name of the process and what is echoed to suit your needs. The brackets around the h in the grep statement cause grep to skip over "grep httpd", it is the equivalent of grep -v grep although more elegant.

-f file(s) to be monitorized

-n number of last line to be printed on the screen

in this example, the content of two files are displayed

Prints the unique IP Addresses as they arrive from an Apache `access.log` file.

The '-W interactive' tells awk to start writing to stdout immediately and not buffer the output.

This command builds on the uniq lines without sorting command (http://www.commandlinefu.com/commands/view/4389/remove-duplicate-entries-in-a-file-without-sorting.)

Useful with new unknown devices or just monitoring, probably useful for the sysadmin. Updates every 2 seconds. More here: http://linuxclisecurity.blogspot.com/2009/12/monitor-kernel-ring-buffer.html.

Put into some file. No special purpouse, just for fun...

Figures out what has changed in the last 12 hours.

Change the author to yourself, change the time since to whatever you want.