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.

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.

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.

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

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.

Find files in a specific date range - in this case, the first half of last year.

-newermt = modification time of the file is more recent than this date

GNU find allows any date specfication that GNU date would accept, e.g.

or

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

Print all columns except the 1st and 3rd.

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

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

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

~$ tar --version

tar (GNU tar) 1.20

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.

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

(relies on 'imagemagick')

This command will convert all .pdf files in a directory into a 800px (wide or height, whichever is smaller) image (with the aspect ratio kept) .jpg.

If the file is named 'example1.pdf' it will be named 'example1.jpg' when it is complete.

This is a VERY worthwhile command! People pay hundreds of dollars for this in the Windows world.

My .jpg files average between 150kB to 300kB, but your's may differ.

While editing a source file in vim, or using vimdiff to compare two or more files, the ':TOhtml' command can be used to export each buffer as an html file, including syntax highlighting and vimdiff colorization. If you are in insert mode in vim, you will have to type

:TOhtml

This will open a new buffer filled with html, which you can then save.

PDF files are simultaneously wonderful and heinous. They are wonderful in being ubiquitous and mostly being cross platform. They are heinous in being very difficult to work with from the command line, search, grep, use only the text inside the PDF, or use outside of proprietary products.

xpdf is a wonderful set of PDF tools. It is on many linux distros and can be installed on OS X. While primarily an open PDF viewer for X, xpdf has the tool "pdftotext" that can extract formated or unformatted text from inside a PDF that has text. This text stream can then be further processed by grep or other tool. The '-' after the file name directs output to stdout rather than to a text file the same name as the PDF.

Make sure you use version 3.02 of pdftotext or later; earlier versions clipped lines.

The lines extracted from a PDF without the "-layout" option are very long. More paragraphs. Use just to test that a pattern exists in the file. With "-layout" the output resembles the lines, but it is not perfect.

xpdf is available open source at http://www.foolabs.com/xpdf/