Commands by camocrazed (9)

  • when using Gnome or KDE, you will have a hard time getting a screenshot of something like a login screen, or any other screen that occurs before the desktop environment is up and monitoring the printscreen key. (this probably applies for other DEs as well, but I haven't used them) What this command is meant to do is take a screenshot of an X window using a command you can run from your virtual terminals (actual text terminals, not just an emulator) To do this: Press CTRL+ALT+F1 to go to a virtual (text) terminal once your login window comes up Login to the virtual terminal and enter the command (you'll have to type it in) You should now have a file called screenshot.png in your home directory with your screenshot in it. For those of you who are new to the virtual terminal thing, you can use CTRL+ALT+F7 to get back to your regular GUI From http://www.gnome.org


    3
    chvt 7 ; sleep 2 ; DISPLAY=:0.0 import -window root screenshot.png
    camocrazed · 2010-08-20 17:28:49 1
  • Broaden your knowledge of the utilities available to you in no particular order whatsoever! Then use that knowledge to create more nifty one-liners that you can post here. =p Takes a random number modulo the number of files in $dir, prints the filename corresponding to that number, and passes it as an argument to man.


    -2
    dir="/bin"; man $(ls $dir |sed -n "$(echo $(( $RANDOM % $(ls $dir |wc -l | awk "{ print $1; }" ) + 1 )) )p")
    camocrazed · 2010-08-20 16:31:50 1
  • This will allow you to convert an audio file to wav format, and send it via ssh to a player on the other computer, which will open and play it there. Of course, substitute your information for the sound file and remote address You do not have to use paplay on the remote end, as it is a PulseAudio thing. If the remote end uses ALSA, you should use aplay instead. If it uses OSS, you should berate them about having a lousy sound system. Also, you're not limited to transmitting encoded as wav either, it's just that AFAIK, most systems don't come with mp3 codecs, but will play wav files fine. If you know SoX is installed on the remote end and has mp3 codecs, you can use the following instead: cat Klaxon.mp3 |ssh thelab@company.com play -t mp3 - this will transmit as mp3. Again, use your specific information. if you're not playing mp3s, use another type with the -t option


    7
    sox Klaxon.mp3 -t wav - |ssh thelab@company.com paplay
    camocrazed · 2010-07-29 23:23:39 0
  • This takes quite a while on my system. You may want to test it out with /bin first, or background it and keep working. If you want to get rid of the "No manual entry for [whatever]" and just have the [whatever], use the following sed command after this one finishes. sed -n 's/^No manual entry for \(.*\)/\1/p' nomanlist.txt Show Sample Output


    -2
    for file in $(ls /usr/bin ) ; do man -w $file 2>> nomanlist.txt >/dev/null ; done
    camocrazed · 2010-07-26 19:39:53 3
  • the tee command does fine with file names, but not so much with file descriptors, such as &2 (stderr). This uses process redirection to tee to the specified descriptor. In the sample output, it's being used to tee to stderr, which is connected with the terminal, and to wc -l, which is also outputting to the terminal. The result is the output of bash --version followed by the linecount Show Sample Output


    5
    tee >(cat - >&2)
    camocrazed · 2010-07-20 17:22:31 3
  • If you're going to use od, here's how to suppress the labels at the beginning. Also, it doesn't output the \x, hence the sed command at the end. Remove it for space separated hex values instead Show Sample Output


    5
    echo -n "text" | od -A n -t x1 |sed 's/ /\\x/g'
    camocrazed · 2010-07-14 15:31:36 1
  • first off, if you just want a random UUID, here's the actual command to use: uuidgen Your chances of finding a duplicate after running this nonstop for a year are about the same as being hit by a meteorite before finishing this sentence The reason for the command I have is that it's more provably unique than the one that uuidgen creates. uuidgen creates a random one by default, or an unencrypted one based on time and network address if you give it the -t option. Mine uses the mac address of the ethernet interface, the process id of the caller, and the system time down to nanosecond resolution, which is provably unique over all computers past, present, and future, subject to collisions in the cryptographic hash used, and the uniqueness of your mac address. Warning: feel free to experiment, but be warned that the stdin of the hash is binary data at that point, which may mess up your terminal if you don't pipe it into something. If it does mess up though, just type reset Show Sample Output


    0
    printf $(( echo "obase=16;$(echo $$$(date +%s%N))"|bc; ip link show|sed -n '/eth/ {N; p}'|grep -o -E '([[:xdigit:]]{1,2}:){5}[[:xdigit:]]{1,2}'|head -c 17 )|tr -d [:space:][:punct:] |sed 's/[[:xdigit:]]\{2\}/\\x&/g')|sha1sum|head -c 32; echo
    camocrazed · 2010-07-14 14:04:53 0
  • Change the number to change the number of spaces. Leaving it out defaults to 8. Leaving out the filename defaults to stdin. And to do it in reverse, you can use the unexpand command.


    -1
    expand -t 2 <filename>
    camocrazed · 2010-07-13 23:04:57 0
  • Same as another one I saw, just with a cleaner sed command Edit: updated the sed command to use the [[:xdigit:]] character class - more portable between locales Note that it will have a newline inserted after every 32 characters of input, due to the output of xxd Show Sample Output


    0
    echo -n 'text' | xxd -ps | sed 's/[[:xdigit:]]\{2\}/\\x&/g'
    camocrazed · 2010-07-13 21:46:30 0

What's this?

commandlinefu.com is the place to record those command-line gems that you return to again and again. 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.

Share Your Commands


Check These Out

create screencast (record text and audio simultaneously) using 'script' and 'arecord'
This shell function takes a single argument, which is used as the base name of the .wav, .timing and .session files created. To create a screencast: $ screencast test type and talk ... then type 'exit' or to exit the screencast. test.wav will contain the audio from your screencast. test.session will contain text and control characters needed to paint the screen test.timing will contain timing information needed to synch individual keystrokes in test.session with the audio. to play back: $ aplay test.wav & scriptreplay test.{timing,session} NOTE: because the shell function uses the variable "$!", and bash likes to expand '!' during history expansion, you will need to turn off bash's history before you enter the shell function. This can be achieved using the command $set +H

Get AWS temporary credentials ready to export based on a MFA virtual appliance
You might want to secure your AWS operations requiring to use a MFA token. But then to use API or tools, you need to pass credentials generated with a MFA token. This commands asks you for the MFA code and retrieves these credentials using AWS Cli. To print the exports, you can use: `awk '{ print "export AWS_ACCESS_KEY_ID=\"" $1 "\"\n" "export AWS_SECRET_ACCESS_KEY=\"" $2 "\"\n" "export AWS_SESSION_TOKEN=\"" $3 "\"" }'` You must adapt the command line to include: * $MFA_IDis ARN of the virtual MFA or serial number of the physical one * TTL for the credentials

For Gentoo users : helping with USE / emerge
This command puts all the flags of the USE variable actually used by the packages you emerged to the file "use", and those which are unused but available to the file "notuse"

Clean swap area after using a memory hogging application
When you run a memory intensive application (VirtualBox, large java application, etc) swap area is used as soon as memory becomes insufficient. After you close the program, the data in swap is not put back on memory and that decreases the responsiveness. Swapoff disables the swap area and forces system to put swap data be placed in memory. Since running without a swap area might be detrimental, swapon should be used to activate swap again. Both swapoff and swapon require root privileges.

Run a command when a file is changed

Install pip with Proxy
Installs pip packages defining a proxy

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"

Install pip with Proxy
Installs pip packages defining a proxy

Recursive grep of all c++ source under the current directory
I like this better than some of the alternatives using -exec, because if I want to change the string, it's right there at the end of the command line. That means less editing effort and more time to drink coffee.

Redefine the cd command's behavior
Often, the very next command after the cd command is 'ls', so why not combine them?. Tested on a Red Hat derivative and Mac OS X Leopard Update: changed ${1:-$HOME} to "${@:-$HOME}" to accomodate directories with spaces in the names


Stay in the loop…

Follow the Tweets.

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.

» http://twitter.com/commandlinefu
» http://twitter.com/commandlinefu3
» http://twitter.com/commandlinefu10

Subscribe to the feeds.

Use your favourite RSS aggregator to stay in touch with the latest commands. There are feeds mirroring the 3 Twitter streams as well as for virtually every other subset (users, tags, functions,…):

Subscribe to the feed for: