Get your colorized grep output in less(1). This involves two things: forcing grep to output colors even though it's not going to a terminal and telling less to handle those properly.

Ever ask yourself "How much data would be lost if I pressed the reset button?"

Scary, isn't it?

SSH can be controlled trough an ~ escape sequence. Example, to terminate the current ssh connection, type a newline, then the ~ character, and last a . character.

This is useful eg when an ssh connection hangs after you reboot a machine and the connection hangs.

Much simpler method. More portable version: ssh host -l user "`cat cmd.txt`"

CCZE is a robust and modular log coloriser, with plugins for apm, exim, fetchmail, httpd, postfix, procmail, squid, syslog, ulogd, vsftpd, xferlog and more.

Examples:

tail -f /var/log/messages | ccze -A

tail -f /var/log/exim4/mainlog | ccze -A

show only the name of the apps that are using internet

This uses Bash's "process substitution" feature to compare (using diff) the output of two different process pipelines.

If you spend most of your time in front of the terminal, leave is a useful reminder. Leave can have absolute form: leave 1555 reminds you to leave at 3:55PM

remotely connects to an https site, fetches the ssl certificate and displays the valid dates for the cert

You have an external USB drive or key.

Apply this command (using the file path of anything on your device) and it will simulate the unplug of this device.

If you just want the port, just type :

echo $(sudo lshw -businfo | grep -B 1 -m 1 $(df "/path/to/file" | tail -1 | awk '{print $1}' | cut -c 6-8) | head -n 1 | awk '{print $1}' | cut -c 5- | tr ":" "-")

youtube-dl has this functionality built in. If you're running an older version of youtube-dl, you can update it using `youtube-dl -U` (although if you have an older version, it probably doesn't download youtube videos anyway.)

youtube-dl --help will show you other options that may come in useful.

Print all columns except the 1st and 3rd.

Negative shell globs already come with bash. Make sure to turn on extended pattern matching with 'shopt -e extglob'.

~$ tar --version

tar (GNU tar) 1.20

this exits bash without saving the history. unlike explicitly disabling the history in some way, this works anywhere, and it works if you decide *after* issuing the command you don't want logged, that you don't want it logged

... $$ ( or ${$} ) is the pid of the current bash instance

this also works perfectly in shells that don't have $$ if you do something like

Forwards localhost:1234 to machine:port, running all data through your chain of piped commands. The above command logs inbound and outbound traffic to two files.

Tip: replace tee with sed to manipulate the data in real time (use "sed -e 's/400 Bad Request/200 OK/'" to tweak a web server's responses ;-) Limitless possibilities.

Even faster without the need for cut... :)

sorts the files by integer megabytes, which should be enough to (interactively) find the space wasters. Now you can

for the above output,

for only the 3 biggest files and so on. It's always a good idea to have this line in your .profile or .bashrc

How often do you make a directory (or series of directories) and then change into it to do whatever? 99% of the time that is what I do.

This BASH function 'md' will make the directory path then immediately change to the new directory. By using the 'mkdir -p' switch, the intermediate directories are created as well if they do not exist.

After the command is done, open the html file in a browser

If you're a moron like me, sometimes your fingers get away from you and you, for example, enter your password when you're already authenticated to ssh-agent, sudo, etc., and your password ends up in shell history. Here's how to get it out.

Useful mainly for debugging or troubleshooting an application or system, such as X11, Apache, Bind, DHCP and others. Another useful switch that can be combined with -mmin, -mtime and so forth is -daystart. For example, to find files that were modified in the /etc directory only yesterday:

Long before tabbed terminals existed, people have been using Gnu screen to open many shells in a single text terminal. Combined with ssh, it gives you the ability to have many open shells with a single remote connection using the above options. If you detach with "Ctrl-a d" or if the ssh session is accidentally terminated, all processes running in your remote shells remain undisturbed, ready for you to reconnect. Other useful screen commands are "Ctrl-a c" (open new shell) and "Ctrl-a a" (alternate between shells). Read this quick reference for more screen commands: http://aperiodic.net/screen/quick_reference