commandlinefu.com is the place to record those command-line gems that you return to again and again.
Delete that bloated snippets file you've been using and share your personal repository with the world. That way others can gain from your CLI wisdom and you from theirs too. All commands can be commented on, discussed and voted up or down.
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Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.
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Wow, didn't really expect you to read this far down. The latest iteration of the site is in open beta. It's a gentle open beta-- not in prime-time just yet. It's being hosted over at UpGuard (link) and you are more than welcome to give it a shot. Couple things:
I think it would be wise if anyone voting down left a comment indicating the reason for that action. Don't keep it to yourself. Thanks.
The output of "echo $PATH" is hard to read, this is much easier. The parentheses ensure that the change to the input field separator (IFS) only happens the the sub shell and not affecting the current shell.
I am new to linux, and I was trying to figure out why I could not sudo with my username in Fedora 10. This command, when run as root, will add a line to the sudoers file allowing the loginname supplied to sudo. The above line will require a password when you sudo, if you wish to sudo without password, use:
echo 'loginname ALL=(ALL) NOPASSWD:ALL' >> /etc/sudoers
instead. you have to run this command as su, and this is just an easier way of using visudo, just adds it right from the terminal.
Issues a scan command on the given scsi host adapter (ex. a fibre channel adapter, in the example above on host0). Output can be watched in the messages log or in "dmesg"
Thanks to OpenSSL, you can quickly and easily generate MD5 hashes for your passwords.
Alternative (thanks to linuxrawkstar and atoponce):
echo -n 'text to be encrypted' | md5sum -
Note that the above method does not utlise OpenSSL.
This will send a test print job to a networked printer.
This command is a bit Linux specific, as --stdin doesn't exist for passwd on many Unix machines. Further, useradd is high level in most distributions and Unix derivatives except for the Debian family of distros, where adduser would be more appropriate. The last bit, with chage, will force the user to change their password on new login.
command to turn off your computer when you go home and can not wait
Replace (as opposed to insert) hex opcodes, data, breakpoints, etc. without opening a hex editor.
HEXBYTES contains the hex you want to inject in ascii form (e.g. 31c0)
OFFSET is the hex offset (e.g. 49cf) into the binary FILE
This is quite usefull in Unix system share via NFS or AppleTalk with OSX clients that like to populate your filesystem with these pesky files
A useful way to generate the MD5 hash for a string by command line
What this does is, if I type ?ssh ? then hit the page-up key, it will complete the line to the last time in my history file that I typed ssh. Hitting page up again will go to the 2nd to last time I typed it. Incredibly handy if you ever type the same commands more than once.
echo "\"\e[6~\": history-search-forward" >> ~/.inputrc
This was useful to generate random passwords to some webpage users, using the sample code, inside a bash script
This is the result of a several week venture without X. I found myself totally happy without X (and by extension without flash) and was able to do just about anything but watch YouTube videos... so this a the solution I came up with for that. I am sure this can be done better but this does indeed work... and tends to work far better than YouTube's ghetto proprietary flash player ;-)
Replace $i with any YouTube ID you want and this will scrape the site for the _real_ URL to the full quality .FLV file on Youtube's server and will then will hand that over to mplayer (or vlc or whatever you want) to be streamed.
In some browsers you can replace $i with just a % or put this in a shell script so all YouTube IDs can be handed directly off to your media player of choice for true streaming without the need for Flash or a downloader like clive. (I do however fully recommend clive if you wish to archive videos instead of streaming them)
If any interest is shown I would be more than happy to provide similar commands for other sites. Most streaming flash players use similar logic to YouTube.
Edit: 05/03/2011 -
Updated line to work with current YouTube. It could be a lot prettier but I will probably follow up with another update when I figure out how to get rid of that pesky Grep. Sed should take that syntax... but it doesn't.
Original (no longer working) command:
mplayer -fs $(echo "http://youtube.com/get_video.php?$(curl -s $youtube_url | sed -n "/watch_fullscreen/s;.*\(video_id.\+\)&title.*;\1;p")")
only for sudo-style systems.
Use this construct instead of I/O re-directors ``>'' or ``>>'' because
sudo only elevates the commands and *not* the re-directors.
***warning: remember that the `tee` command will clobber
file contents unless it is given the ``-a'' argument
Also, for extra security, the "left" command is still run unprivileged.
This is a simple example of using proper command nesting using $() over ``. There are a number of advantages of $() over backticks. First, they can be easily nested without escapes:
program1 $(program2 $(program3 $(program4)))
program1 `program2 \`program3 \`program4\`\``
Second, they're easier to read, then trying to decipher the difference between the backtick and the singlequote: `'. The only drawback $() suffers from is lack of total portability. If your script must be portable to the archaic Bourne shell, or old versions of the C-shell or Korn shell, then backticks are appropriate, otherwise, we should all get into the habit of $(). Your future script maintainers will thank you for producing cleaner code.
This will print out the third column of every line in FILE. Useful for many files in /proc or *csv data.
This example summarize size of all pdf files in /tmp directory and its subdirectories (in bytes).
Replace "/tmp" with directory path of your choice and "\*pdf" or even "-iname \*pdf" with your own pattern to match specific type of files. You can replace also parameter for du to count kilo or megabytes, but because of du rounding the sum will not be correct (especially with lot of small files and megabytes counting).
In some cases you could probably use sth like this:
du -cb `find /tmp -type f -iname \*pdf`|tail -n 1
But be aware that this second command CANNOT count files with spaces in their names and it will cheat you, if there are some files matching the pattern that you don't have rights to read. The first oneliner is resistant to such problems (it will not count sizes of files which you cant read but will give you correct sum of rest of them).
Compares two versions with dpkg. It is not always obvious what version dpkg/apt will consider to be more recent. Operators include the following :
* These treat an empty version as earlier than any version: lt le eq ne ge gt.
* These treat an empty version as later than any version: lt-nl le-nl ge-nl gt-nl.
* These are provided only for compatibility with control file syntax: < > >.
This command doesn't output anything. It only returns with status 0 or 1, hence the echo "y" || echo "n" to get an output.
I use this command on my machines running VMware Server to print out the state of all registered Virtual machines.