Commands tagged Linux (266)

  • Have netcat listen on port 8000, point browser to http://localhost:8000/ and you see the information sent. netcat terminates as soon as your browser disconnects. I tested this command on my Fedora box but linuxrawkstar pointed out that he needs to use nc -l -p 8000 instead. This depends on the netcat version you use. The additional '-p' is required by GNU netcat that for example is used by Debian but not by the OpenBSD netcat port used by my Fedora system. Show Sample Output


    2
    nc -l 8000
    penpen · 2009-03-25 23:09:38 6
  • In the above example 'muspi merol' (the output of the first rev command) is sent to stderr and 'lorem ipsum' (the output of the second rev command) is sent to stdout. rev reverse lines of a file or files. This use of tee allows testing if a program correctly handles its input without using files that hold the data. Show Sample Output


    2
    rev <<< 'lorem ipsum' | tee /dev/stderr | rev
    penpen · 2009-03-31 13:12:09 7
  • There was another line that was dependent on having un-named screen sessions. This just wouldn't do. This one works no matter what the name is. A possible improvement would be removing the perl dependence, but that doesn't effect me.


    2
    for i in `screen -ls | perl -ne'if(/^\s+\d+\.([^\s]+)/){print $1, " "}'`; do gnome-terminal -e "screen -x $i"; done
    hank · 2009-04-25 22:39:24 7
  • Shell timeout variables (TMOUT) can be very liberal about what is classified as 'activity', like having an editor open. This command string will terminate the login shell for an user with more than a day's idle time.


    2
    fuser -k `who -u | awk '$6 == "old" { print "/dev/"$2'}`
    lbonanomi · 2009-09-07 03:36:43 5
  • This command gives you the charset of a text file, which would be handy if you have no idea of the encoding. Show Sample Output


    2
    file -i <textfile>
    juvenn · 2009-09-08 01:33:19 4
  • This command will transcode a MythTV recording. The target device is a Google Nexus One mobile phone. My recordings are from a HDHomerun with Over The Air content. Plays back nicely on the N1.


    2
    ffmpeg -i /var/lib/mythtv/pretty/Chuck20100208800PMChuckVersustheMask.mpg -s 800x480 -vcodec mpeg4 -acodec libfaac -ac 2 -ar 16000 -r 13 -ab 32000 -aspect 16:9 Chuck20100208800PMChuckVersustheMask.mp4
    PLA · 2010-02-12 12:11:02 7
  • extension to tali713's random fact generator. It takes the output & sends it to notify-osd. Display time is proportional to the lengh of the fact.


    2
    wget randomfunfacts.com -O - 2>/dev/null | grep \<strong\> | sed "s;^.*<i>\(.*\)</i>.*$;\1;" | while read FUNFACT; do notify-send -t $((1000+300*`echo -n $FUNFACT | wc -w`)) -i gtk-dialog-info "RandomFunFact" "$FUNFACT"; done
    mtron · 2010-04-02 09:43:32 4
  • A little aptitude magic. Note: this will remove images AND headers. If you just want to remove images: aptitude remove ?and(~i~nlinux-im ?not(~n`uname -r`)) I used this in zsh without any problems. I'm not sure how other shells will interpret some of the special characters used in the aptitude search terms. Use -s to simulate.


    2
    aptitude remove ?and(~i~nlinux-(im|he) ?not(~n`uname -r`))
    dbbolton · 2010-06-11 22:57:09 6
  • probably only works if you have one graphics card. used this: http://www.cyberciti.biz/faq/howto-find-linux-vga-video-card-ram/ as reference can be expanded, for example: lspci -v -s `lspci | awk '/VGA/{print $1}'` | sed -n '/Memory.*, prefetchable/s/.*\[size=\([^]]\+\)\]/\1/p' will just get the amount of prefetchable memory compare to: lshw -C display which does not give the size (it does give byte ranges and you could calculate the size from that, but that's a pain) Also uses a command which is not standard on linux; wheras lspci is a core utility provided by most systems Show Sample Output


    2
    lspci -v -s `lspci | awk '/VGA/{print $1}'`
    infinull · 2010-10-26 17:45:14 9
  • Specify the size in bytes using the 'c' option for the -size flag. The + sign reads as "bigger than". Then execute du on the list; sort in reverse mode and show the first 10 occurrences. Show Sample Output


    2
    find /myfs -size +209715200c -exec du -m {} \; |sort -nr |head -10
    arlequin · 2011-07-07 21:12:46 3
  • this will open a new tab in firefox for every line in a file the sleep is removable but i found that if you have a large list of urls 50+, and no sleep, it will try to open all the urls at once and this will cause them all to load a lot slower, also depending on the ram of your system sleep gives you a chance to close the tabs before they overload your ram, removing & >2/dev/null will yield unpredictable results.


    2
    for line in `cat $file`; do firefox -new-tab "$line" & 2>/dev/null; sleep 1; done
    hamsolo474 · 2011-11-12 13:47:24 3
  • Converts a number of bytes provided as input, to a human readable number. Show Sample Output


    2
    human_filesize() { awk -v sum="$1" ' BEGIN {hum[1024^3]="Gb"; hum[1024^2]="Mb"; hum[1024]="Kb"; for (x=1024^3; x>=1024; x/=1024) { if (sum>=x) { printf "%.2f %s\n",sum/x,hum[x]; break; } } if (sum<1024) print "1kb"; } '}
    ArtBIT · 2011-12-02 18:21:20 3
  • "What it actually shows is going to be dependent on the commands you've previously entered. When you do this, bash looks for the last command that you entered that contains the substring "ls", in my case that was "lsof ...". If the command that bash finds is what you're looking for, just hit Enter to execute it. You can also edit the command to suit your current needs before executing it (use the left and right arrow keys to move through it). If you're looking for a different command, hit Ctrl+R again to find a matching command further back in the command history. You can also continue to type a longer substring to refine the search, since searching is incremental. Note that the substring you enter is searched for throughout the command, not just at the beginning of the command." - http://www.linuxjournal.com/content/using-bash-history-more-efficiently Show Sample Output


    2
    <ctrl+r>
    *deleted* · 2012-04-15 16:42:32 5
  • list the top 15 folders by decreasing size in MB Show Sample Output


    2
    du -xB M --max-depth=2 /var | sort -rn | head -n 15
    bouktin · 2013-05-23 10:45:21 6
  • Optionally, pipe the output into http://sed.sourceforge.net/grabbag/scripts/html2iso.sed Or: wget -qO - http://www.asciiartfarts.com/random.cgi | sed -n '//,//p' | sed -n '/ Show Sample Output


    2
    wget -qO - http://www.asciiartfarts.com/random.cgi | sed -n '/<pre>/,/<\/pre>/p' | sed -n '/<table*/,/<\/table>/p' | sed '1d' | sed '$d' | recode html..ascii
    krunktron · 2013-08-17 19:42:47 9

  • 2
    grep -v rootfs /proc/mounts > /etc/mtab
    ohe · 2014-01-21 14:28:12 7
  • To show ipv6 instead, use [[ -6 ]] instead of [[ -4 ]] ip -o -6 a s | awk -F'[ /]+' '$2!~/lo/{print $4}' To show only the IP of a specific interface, in case you get more than one result: ip -o -4 a s eth0 | awk -F'[ /]+' '$2!~/lo/{print $4}' ip -o -4 a s wlan0 | awk -F'[ /]+' '$2!~/lo/{print $4}' Show Sample Output


    2
    ip -o -4 a s | awk -F'[ /]+' '$2!~/lo/{print $4}'
    paulera · 2015-02-13 11:19:31 11

  • 2
    tr '\0' ' ' </proc/21679/cmdline ; echo
    pdxdoughnut · 2015-09-25 22:08:31 16
  • Assumes you've downloaded Toni Corvera's vcs script (http://p.outlyer.net/vcs), have it in your PATH, and have installed the script's dependencies. Generates a video contact sheet of 24 thumbnails and 3 thumbnails per column. The bold font and white-on-black color scheme keeps the text readable at the chosen 70% JPEG compression quality, which keeps the file size at a manageable level. You can go even lower with the quality and get a good looking result.


    2
    vcs -c 3 -H 220 -n 24 -dt -ds -dp -j --anonymous -O bg_heading=black -O bg_sign=black -O fg_heading=white -O fg_heading=white -O fg_sign=white -O fg_title=white -O font_heading=DejaVu-Sans-Bold -O quality=70
    Negate · 2018-06-06 00:49:25 218
  • Uses the shell builtin `declare` with the '-f' flag to output only functions to grep out only the function names. You can use it as an alias or function like so: alias shfunctions="builtin declare -f | command grep --color=never -E '^[a-zA-Z_]+\ \(\)'" shfunctions () { builtin declare -f | command grep --color=never -E '^[a-zA-Z_]+\ \(\)'; } Show Sample Output


    2
    builtin declare -f | command grep --color=never -E '^[a-zA-Z_]+\ \(\)'
    sciro · 2018-07-23 05:24:04 1006
  • explanation: grep -- displays process ids -v -- negates the matching, displays all but what is specified in the other options -u -- specifies the user to display, or in this case negate The process loops through all PIDs that are found by pgrep, then orders a forced kill to the processes in numerical order, effectively killing the parent processes first including the shells in use which will force the users to logout. Tested on Slackware Linux 12.2 and Slackware-current


    1
    for i in $(pgrep -v -u root);do kill -9 $i;done
    lostnhell · 2009-03-24 02:54:52 8
  • and, a lot uglier, with sed: ifconfig | sed -n '/inet addr:/s/[^:]\+:\(\S\+\).*/\1/p' Edit: Wanted to be shorter than the perl version. Still think that the perl version is the best..


    1
    ifconfig | awk -F':| +' '/ddr:/{print $4}'
    0x89 · 2009-07-25 22:51:08 4
  • The initial version of this command also outputted extra empty lines, so it went like this: 192.168.166.48 127.0.0.1 This happened on Ubuntu, i haven't tested on anything else. Show Sample Output


    1
    ifconfig | awk '/ddr:[0-9]/ {sub(/addr:/, ""); print $2}'
    danny_b85 · 2009-07-31 09:30:54 3
  • default stack size is 10M. This makes your multithread app filling rapidly your memory. on my PC I was able to create only 300thread with default stack size. Lower the default stack size to the one effectively used by your threads, let you create more. ex. putting 64k I was able to create more than 10.000threads. Obviously ...your thread shouldn't need more than 64k ram!!!


    1
    ulimit -s 64
    ioggstream · 2009-08-06 10:40:25 5
  • you must be in the directory to analyse report all files and links in the currect directory, not recursively. this find command ahs been tested on hp-ux/linux/aix/solaris. Show Sample Output


    1
    find . \( ! -name . -prune \) \( -type f -o -type l \)
    mobidyc · 2009-09-12 15:58:56 11
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convert a .wmv to a .avi

Simple Video Surveillance by email
This takes a picture (with the web cam) every 5 minutes, and send the picture to your e-mail. Some systems support mail -a "References: " so that all video surveillance emails are grouped in a single email thread. To keep your inbox clean, it is still possible to filter and move to trash video surveillance emails (and restore these emails only if you really get robbed!) For instance with Gmail, emails sent to me+trash@gmail.com can be filtered with "Matches: DeliveredTo:me+trash@gmail.com"

Print average GPU core temperature

Create Encrypted WordPress MySQL Backup without any DB details, just the wp-config.php
The coolest way I've found to backup a wordpress mysql database using encryption, and using local variables created directly from the wp-config.php file so that you don't have to type them- which would allow someone sniffing your terminal or viewing your shell history to see your info. I use a variation of this for my servers that have hundreds of wordpress installs and databases by using a find command for the wp-config.php file and passing that through xargs to my function.

Commit command to history file immedeately after execution
This could be added to .bashrc. Background: Linux usually saves history only on clean exit of shell. If shell ends unclean, history is lost. Also numerous terminals might confuse their history. With this variable set, history is immedeately written, accessible to all other open shells.

clone directory structure
dir1 and all its subdirs and subdirs of subdirs ... but *no files* will be copied to dir2 (not even symbolic links of files will be made). To preserve ownerships & permissions: $ cp -Rps dir1 dir2 Yes, you can do it with $ rsync -a --include '*/' --exclude '*' /path/to/source /path/to/dest too, but I didn't test if this can handle attributes correctly (experiment rsync command yourself with --dry-run switch to avoid harming your file system) You must be in the parent directory of dir1 while executing this command (place dir2 where you will), else soft links of files in dir2 will be made. I couldn't find how to avoid this "limitation" (yet). Playing with recursive unlink command loop maybe? PS. Bash will complain, but the job will be done.

Using numsum to sum a column of numbers.
numsum is part of of the num-utils package, which is available in some Linux distros and can also be downloaded at http://suso.suso.org/xulu/Num-utils. It contains about 10 different programs for dealing with numbers from the command line. Obviously you can do a lot of things that the num-utils programs do in awk, sed, bash, perl scripts, but num-utils are there so that you don't have to remember the syntax for more complex operations and can just think: compute the sum, average, boundary numbers, etc.

sshfs usage
you can use this command for mounting local directory to a remost directory..

Display current time in requested time zones.
The time zone names come from the tz database which is usually found at /usr/share/zoneinfo.

Decrypt passwords from Google Chrome and Chromium.
Read this before you down voting and comment that it is not working -> Wont work on latest versions ~75> since database file is locked and has to be decrypted. This is useful if you have an old hdd with a chrome installation and want to decrypt your old passwords fast.


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