Add Line Numbers to “cat” Output

cat can be used to print the contents of a file in a Terminal, and it’s often useful to number each line of the output (including empty lines). Adding line numbers is as simple as adding the -n switch to the command: cat -n filename.txt Example Output, with -n switch: $ cat -n filename.txt 1 Line …

Using grep and Ignoring Case (Case Insensitive grep)

grep is a great way to find phrases, words, and characters in text.  One of the biggest stumbling blocks is case – is the word “Hello”, “hello”, “HELLO”, or even “HeLLo”?  All of these are different, and a “grep “Hello”” would only find lines containing the first “Hello” example. You can, however, exclude case from …

Using dig to Query a Specific DNS Server (Name Server) Directly (Linux, BSD, OSX)

There may be occasions when you wish to query a DNS server directly.  I often do it before changing DNS servers for a domain; I’ll setup the new records on the new DNS servers, and then query them directly to ensure they are returning the correct records. I recommend that anyone running DNS services for …

Using grep to Exclude Lines Containing Certain Characters/Text

I like to watch Apache log files using tail -f but they often get filled up with data I don’t want/need to see – like, when I access the web site. grep is a great tool to search for certain information in text files – but it can also exclude certain pieces of information which …

Kill a GNU Screen Session from the Command Line

This article is about GNU Screen – you can read about GNU Screen here: http://www.gnu.org/software/screen/ There may be times when you have multiple, or even a single, screen session which you want to kill without attaching to it and ending it as you normally would. You can kill a screen session using the session ID or the …

Finding out when (and where from) a user last logged into a Linux/BSD machine

There may be times when you want to find out when and where from a user last logged into a Linux or BSD machine. Of course, you could trawl through auth logs, but there is a quicker way by using “lastlog“. lastlog is a command which shows you the last login time and also from …

SSH Client: Saving Server Configuration (Alias, Port, Username)

There may be occasions where you want to connect to a host with a long host name, for example ssh servername.example.com – now it’s not massive, but it’s not as quick as ssh servername If you’ve been following droptips.com, you’ll have noticed my other post about setting the port number in the SSH config file …

SSH Client: Automatically Connect to a Servers’ Non-Standard Port

If you run an SSH server, or many SSH servers, then you may have set the SSH daemon to run on a non-standard port. SSH normally listens on port 22, but with the large amount of script/bot attacks now on this port, attempting random logins, changing it to something different is a quick way to …