Commands tagged unix (62)

  • "Sample output" shows a minimalistic configuration file. Show Sample Output


    2
    rsync --daemon --port 1234 --no-detach -v --config rsyncd.conf
    denilsonsa · 2016-08-21 22:10:17 0
  • Ever needed to test firewalls but didn't have netcat, telnet or even FTP? Enter /dev/tcp, your new best friend. /dev/tcp/(hostname)/(port) is a bash builtin that bash can use to open connections to TCP and UDP ports. This one-liner opens a connection on a port to a server and lets you read and write to it from the terminal. How it works: First, exec sets up a redirect for /dev/tcp/$server/$port to file descriptor 5. Then, as per some excellent feedback from @flatcap, we launch a redirect from file descriptor 5 to STDOUT and send that to the background (which is what causes the PID to be printed when the commands are run), and then redirect STDIN to file descriptor 5 with the second cat. Finally, when the second cat dies (the connection is closed), we clean up the file descriptor with 'exec 5>&-'. It can be used to test FTP, HTTP, NTP, or can connect to netcat listening on a port (makes for a simple chat client!) Replace /tcp/ with /udp/ to use UDP instead.


    15
    exec 5<>/dev/tcp/time.nist.gov/13; cat <&5 & cat >&5; exec 5>&-
    tyzbit · 2015-07-30 21:12:38 9
  • This will show all changes in all log files under /var/log/ that are regular files and don't end with `gz` nor with a number Show Sample Output


    4
    find /var/log -type f -iregex '.*[^\.][^0-9]+$' -not -iregex '.*gz$' 2> /dev/null | xargs tail -n0 -f | ccze -A
    rubo77 · 2014-07-29 17:11:17 0
  • In this example, 192.168.12.50 is the host that should be routed via the VPN and "ppp0" is the name of the VPN network interface (ifconfig shows you the list of network interfaces). Can be a IP or domain name. Show Sample Output


    0
    sudo /sbin/route add -host 192.168.12.50 -interface ppp0
    jifilis · 2014-04-13 00:17:53 0
  • Lists directory size up to a maximum traversal depth on systems like IBM AIX, where the du command doesn't have Linux's --max-depth option. AIX's du uses -g to display directory size on gigabytes, -m to use megabytes, and -k to use kilobytes. tr### is a Perl function that replaces characters and returns the amount of changed characters, so in this case it will return how many slashes there were in the full path name. Show Sample Output


    0
    du -g | perl -ne 'print if (tr#/#/# == <maximum depth>)'
    RAKK · 2014-02-15 07:33:36 0
  • This example is taken from Cygwin running on Win7Ent-64. Device names will vary by platform. Both commands resulted in identical files per the output of md5sum, and ran in the same time down to the second (2m45s), less than 100ms apart. I timed the commands with 'time', which added before 'dd' or 'readom' gives execution times after the command completes. See 'man time' for more info...it can be found on any Unix or Linux newer than 1973. Yeah, that means everywhere. readom is supposed to guarantee good reads, and does support flags for bypassing bad blocks where dd will either fail or hang. readom's verbosity gave more interesting output than dd. On Cygwin, my attempt with 'readom' from the first answer actually ended up reading my hard drive. Both attempts got to 5GB before I killed them, seeing as that is past any CD or standard DVD. dd: 'bs=1M' says "read 1MB into RAM from source, then write that 1MB to output. I also tested 10MB, which shaved the time down to 2m42s. 'if=/dev/scd0' selects Cygwin's representation of the first CD-ROM drive. 'of=./filename.iso' simply means "create filename.iso in the current directory." readom: '-v' says "be a little noisy (verbose)." The man page implies more verbosity with more 'v's, e.g. -vvv. dev='D:' in Cygwin explicitly specifies the D-drive. I tried other entries, like '/dev/scd0' and '2,0', but both read from my hard drive instead of the CD-ROM. I imagine my LUN-foo (2,0) was off for my system, but on Cygwin 'D:' sort of "cut to the chase" and did the job. f='./filename.iso' specifies the output file. speed=2 simply sets the speed at which the CD is read. I also tried 4, which ran the exact same 2m45s. retries=8 simply means try reading a block up to 8 times before giving up. This is useful for damaged media (scratches, glue lines, etc.), allowing you to automatically "get everything that can be copied" so you at least have most of the data. Show Sample Output


    -1
    dd bs=1M if=/dev/scd0 of=./filename.iso OR readom -v dev='D:' f='./filename.iso' speed=2 retries=8
    scotharkins · 2013-10-23 15:53:27 0
  • This command is used to verify a sha256sum-formatted file hash list on IBM AIX or any other UNIX-like OS that has openssl but doesn't have sha256sum by default. Steps: 1: Save to the filesystem a script that: A: Receives as arguments the two parts of one line of a sha256sum listing B: Feeds a file into openssl on SHA256 standard input hash calculation mode, and saves the result C: Compares the calculated hash against the one received as argument D: Outputs the result in a sha256sum-like format 2: Make the script runnable 3: Feed the sha256sum listing to xargs, running the aforementioned script and passing 2 arguments at a time Show Sample Output


    0
    echo '#! /usr/bin/ksh\ncat $2 | openssl dgst -sha256 | read hashish; if [[ $hashish = $1 ]]; then echo $2: OK; else echo $2: FAILED; fi;' > shacheck; chmod +x shacheck; cat hashishes.sha256 | xargs -n 2 ./shacheck;
    RAKK · 2013-09-18 21:51:20 2
  • This command is for producing GNU sha256sum-compatible hashes on UNIX systems that don't have sha256sum but do have OpenSSL, such as stock IBM AIX. 1.- Saves a wrapper script for UNIX find that does the following: A.- Feeds a file to openssl on SHA256 hash calculation mode B.- Echoes the output followed by the filename 2.- Makes the file executable 3.- Runs find on a directory, only processing files, and running on each one the wrapper script that calculates SHA256 hashes Pending is figuring out how to verify a sha256sum file on a similar environment. Show Sample Output


    0
    echo '#! /usr/bin/ksh\necho `cat $1 | openssl dgst -sha256` $1' > sslsha256; chmod +x sslsha256; find directory -type f -exec ./sslsha256 \{\} \;
    RAKK · 2013-09-18 17:37:50 0
  • Replace '/tmp/file 1.txt' '/tmp/file 2.jpg' with "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS" for Nautilus script Or with %F for Thunar action If you linking the symlinks itself, but want to link to source files instead of symlinks, use "`readlink -m "$i"`" instead of "$i" like this: for i in '/tmp/file 1.txt' '/tmp/file 2.jpg'; do ln -s "`readlink -m "$i"`" "$i LINK"; done ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Show Sample Output


    0
    for i in '/tmp/file 1.txt' '/tmp/file 2.jpg'; do ln -s "$i" "$i LINK"; done
    qwertyroot · 2013-08-02 08:30:50 0
  • while commandt do command command ... done {commandt is executed and its exit status tested.} for i in 1 2 3 > do > echo $i > done Show Sample Output


    -3
    i=0; while [ $i -lt 100 ]; do echo "test, ttest, tttest-${i}" >> kk.file; i=`expr $i + 1`; done
    kaushalmehra · 2012-09-13 21:46:18 0
  • sed '$ d' foo.txt.tmp ...deletes last line from the file


    -2
    cp foo.txt foo.txt.tmp; sed '$ d' foo.txt.tmp > foo.txt; rm -f foo.txt.tmp
    kaushalmehra · 2012-09-13 20:57:40 2
  • Output lines starting at line 2.


    3
    tail -n +2 foo.txt
    kaushalmehra · 2012-09-13 20:54:36 0
  • This physical volumne - hdisk1 - has TOTAL PPs:11999 (1535872 megabytes) -> 1.5 TB This physical volumne - hdisk1 - has -> 60 GB Show Sample Output


    0
    lspv hdisk1
    kaushalmehra · 2012-09-13 15:40:58 0
  • Like the above, but runs a single rm command


    0
    find /backup/directory -name "FILENAME_*" -mtime +15 -exec rm -vf {} +
    mrfixit42 · 2012-08-03 04:20:53 0
  • This will check if there are any empty directories, or newly emptied directories, in a list of directories. It will then delete all of those directories. It works with gnu find and OSX/BSD find.


    0
    for foo in <list of directories>; do while find $foo -type d -empty 2>/dev/null| grep -q "."; do find $foo -type d -empty -print0 | xargs -0 rmdir; done; done
    ClashTheBunny · 2012-05-23 08:09:16 0

  • 3
    find . -iname *.java -type f -exec bash -c "iconv -f WINDOWS-1252 -t UTF-8 {} > {}.tmp " \; -exec mv {}.tmp {} \;
    miguelbaldi · 2012-01-12 20:00:26 0

  • 0
    find . -type f -exec awk '/linux/ { printf "%s %s: %s\n",FILENAME,NR,$0; }' {} \;
    Neo23x0 · 2011-11-29 12:32:06 1
  • An example config file is placed in the sample output along with the command line call to use it. The rsync daemon here is setup on the destination, thus requiring the read only = false flag. Also it uses uid and gid of root, change as required. Show Sample Output


    -3
    rsync --daemon --port 9999 --no-detach -v --config .rsyncd.conf
    pykler · 2011-09-22 20:48:31 0
  • 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 0

  • 2
    find /var/log -iregex '.*[^\.][^0-9]+$' -not -iregex '.*gz$' 2> /dev/null | xargs tail -n0 -f | ccze -A
    brejktru · 2011-04-17 18:09:25 0
  • Will rot 13 whatever parameter follows 'rot13', whether it is a string or a file. Additionally, it will rot 5 each digit in a number


    -5
    function rot13 { if [ -r $1 ]; then cat $1 | tr '[N-ZA-Mn-za-m5-90-4]' '[A-Za-z0-9]'; else echo $* | tr '[N-ZA-Mn-za-m5-90-4]' '[A-Za-z0-9]'; fi }
    twjolson · 2011-03-18 09:59:41 0

  • 10
    alias rot13="tr a-zA-Z n-za-mN-ZA-M"
    mathias · 2011-03-17 11:21:19 0
  • list top committers (and number of their commits) of svn repository. in this example it counts revisions of current directory. Show Sample Output


    2
    svn log -q | grep '^r[0-9]' | cut -f2 -d "|" | sort | uniq -c | sort -nr
    kkapron · 2011-01-03 15:23:08 0
  • if you dont want to alias also then you can do killall rapidly_spawning_process ; !! ; !! ; !!


    3
    alias a=" killall rapidly_spawning_process"; a; a; a;
    raj77_in · 2010-05-20 02:33:28 0
  • Use this if you can't type repeated killall commands fast enough to kill rapidly spawning processes. If a process keeps spawning copies of itself too rapidly, it can do so faster than a single killall can catch them and kill them. Retyping the command at the prompt can be too slow too, even with command history retrieval. Chaining a few killalls on single command line can start up the next killall more quickly. The first killall will get most of the processes, except for some that were starting up in the meanwhile, the second will get most of the rest, and the third mops up.


    -2
    killall rapidly_spawning_process ; killall rapidly_spawning_process ; killall rapidly_spawning_process
    unixmonkey7434 · 2010-05-20 00:26:10 2
  •  1 2 3 > 

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



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: