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Open Port Check
also could specify port number: lsof -ni TCP:80

Find the package that installed a command

To play a file at 1.5 times normal speed without increasing the pitch

Display IP : Count of failed login attempts
The lastb command presents you with the history of failed login attempts (stored in /var/log/btmp). The reference file is read/write by root only by default. This can be quite an exhaustive list with lots of bots hammering away at your machine. Sometimes it is more important to see the scale of things, or in this case the volume of failed logins tied to each source IP. The awk statement determines if the 3rd element is an IP address, and if so increments the running count of failed login attempts associated with it. When done it prints the IP and count. The sort statement sorts numerically (-n) by column 3 (-k 3), so you can see the most aggressive sources of login attempts. Note that the ':' character is the 2nd column, and that the -n and -k can be combined to -nk. Please be aware that the btmp file will contain every instance of a failed login unless explicitly rolled over. It should be safe to delete/archive this file after you've processed it.

Convert seconds to [DD:][HH:]MM:SS
Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Unzip 25 zip files files at once

Suspend, background, and foreground a process
1. Start a process, such as 'top' command 2. # suspend process {ctrl-Z} 3. # background process bg 4. # list all backgrounded jobs jobs 5. # bring it back to foreground fg

Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

A formatting test for David Winterbottom: improving commandlinefu for submitters
Commandlinefu.com is great but has a few bugs when people are submitting new commands: . 1. There is no preview button. This was a minor inconvenience before, but now is a major problem since new commands won't show up to be edited until they have been moderated. . 2. White space in the description field and in the comments is almost completely lost. People resort to using periods in between paragraphs to force a line break. Indentation of code is ridiculous. . 3. Many characters get munged. . 3a. For example, a less than character in the description gets read as an HTML tag and discarded. In order to type a less than, I've had to type "<" (I hope that comes out right). Unfortunately, when re-editing a command, the HTML entity is turned into a literal less than character, which I have to change back by hand before saving. 3b. Some unicode characters work in the description field, but turn into ugly literal HTML strings when put in the sample output or in an additional command using the $ prefix. . For example, here is a unicode character: ❥ $ Here is the same character after a dollar sign: ❥ . 3c. Some unicode characters don't work anywhere. Bizarrely, it appears to be the most commonly needed ones, such as Latin-1 accented characters. Here are some examples, . Bullet: ?, Center dot: ?, Umlaut u: ?. . 4. Here is an example of the greater than, >, and less than,

NICs, IPs, and Mac
Needed to get the Mac of various devices on a solaris box, but didn't have root. This command used awk to display the Network device, the IP, and the MAC a line at a time.


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