Commands by tyzbit (12)

  • Tails a log and replaces it line-by-line according to whatever you want to replace. Useful if the file writing to the log can't be modified, so you need to modify its output instead. Show Sample Output


    0
    tail -F logfile|while read l; do sed 's/find/replace/g' <<< $l; done
    tyzbit · 2020-08-07 12:26:39 29
  • Colorify colors input by converting the text to a number and then performing modulo 7 on it. This resulting number is used as the color escape code. This can be used to color the results of commands with complex outputs (like "482279054165371") so if any of the digits change, there's a good chance the color will change too. I say good chance because there's only 7 unique colors here, so assuming you were watching random numbers, there would be a 6/7 chance that the color would change when the number changed. This should really only be used to help quickly identify when things change, but should not be the only thing relied upon to positively assert that an output has not changed. Show Sample Output


    1
    function colorify() { n=$(bc <<< "$(echo ${1}|od -An -vtu1 -w100000000|tr -d ' ') % 7"); echo -e "\e[3${n}m${1}\e[0m"; }
    tyzbit · 2020-08-06 15:17:45 24
  • Get the total RESIDENT memory used by processes of a specific name. This means this is the MINIMUM used by a process, but some memory could be paged out to swap. Show Sample Output


    0
    pids=$(pidof chrome); for p in ${pids[@]}; do cat /proc/$p/status | grep -i vmrss | awk '{print $2}'; done | while read m; do let t=$t+$m; echo $t; done | echo "$(tail -n 1) kB"
    tyzbit · 2018-04-08 16:43:35 1
  • simple jq one-liner to convert from configmaps to secrets (which require the values to be base64 encoded). To automatically pull the config map, convert it, and re-upload the corresponding secret: kubectl get --export -o json cm [configmap name] | jq 'with_entries(if .key == "data" then .value=(.value | to_entries | map( { (.key): (.value|@base64) } ) | add ) elif .key == "kind" then .value="Secret" else . end)' > secret.json; kubectl create -f secret.json Show Sample Output


    0
    cat configmap.json | jq 'with_entries(if .key == "data" then .value=(.value | to_entries | map( { (.key): (.value|@base64) } ) | add ) elif .key == "kind" then .value="Secret" else . end)'
    tyzbit · 2017-12-11 19:18:25 0
  • This is a bit of a bash hack to catch STDERR and append a log level to it. So for example, if your script has pseudo loglevels like so: echo "INFO - finding files" [ -f ${files} ] || echo "WARN - no files found" Any subcommands that write to STDERR will screw that up Adding 2> >(fb=$(dd bs=1 count=1 2>/dev/null | od -t o1 -A n); [ "$fb" ] && err=$(printf "\\${fb# }"; cat) && echo "ERROR - $err") to the command does the following: 2> Redirect STDERR >( Spawn a subshell (STDERR is then redirected to the file descriptor for this subshell) fb=$(....) get the first byte of input [ "$fb" ] test if there's a first byte && err=$(printf....) save the output to the $err variable && echo "ERROR - $err" append your pseudo loglevel and the error message Heavily borrowed from https://unix.stackexchange.com/questions/33049/check-if-pipe-is-empty-and-run-a-command-on-the-data-if-it-isnt Show Sample Output


    0
    [command] 2> >(fb=$(dd bs=1 count=1 2>/dev/null | od -t o1 -A n); [ "$fb" ] && err=$(printf "\\${fb# }"; cat) && echo "ERROR - $err")
    tyzbit · 2017-10-16 22:22:42 1
  • Ever needed to test firewalls but didn't have netcat, telnet or even FTP? Enter /dev/tcp, your new best friend. /dev/tcp/(hostname)/(port) is a bash builtin that bash can use to open connections to TCP and UDP ports. This one-liner opens a connection on a port to a server and lets you read and write to it from the terminal. How it works: First, exec sets up a redirect for /dev/tcp/$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
  • Most distributions alias cp to 'cp -i', which means when you attempt to copy into a directory that already contains the file, cp will prompt to overwrite. A great default to have, but when you mean to overwrite thousands of files, you don't want to sit there hitting [y] then [enter] thousands of times. Enter the backslash. It runs the command unaliased, so as in the example, cp will happily overwrite existing files much in the way mv works. Show Sample Output


    1
    \[command]
    tyzbit · 2015-01-15 18:31:50 0
  • Use this command to watch apache access logs in real time to see what pages are getting hit. Show Sample Output


    0
    tail -f access_log | awk '{print $1 , $12}'
    tyzbit · 2014-12-24 14:15:52 1
  • This is not exhaustive but after checking /etc/cron* is a good way to see if there are any other jobs any users may have set. Note: this is a repost from a comment "flatcap" made on http://www.brpent.com/commands/view/3726/print-crontab-entries-for-all-the-users-that-actually-have-a-crontab#comment, for which I am grateful and I take no credit.


    0
    for USER in /var/spool/cron/*; do echo "--- crontab for $USER ---"; cat "$USER"; done
    tyzbit · 2014-12-11 19:48:46 1
  • This checks the system load every second and if it's over a certain threshold (.8 in this example), it spits out the date, system loads and top 4 processes sorted by CPU. Additionally, the \a in the first echo creates an audible bell.


    0
    while sleep 1; do if [ $(echo "$(cat /proc/loadavg | cut -d' ' -f1) > .8 " | bc) -gt 0 ]; then echo -e "\n\a"$(date)" \e[5m"$(cat /proc/loadavg)"\e[0m"; ps aux --sort=-%cpu|head -n 5; fi; done
    tyzbit · 2014-12-08 15:44:40 0
  • Wakes up a computer on your LAN with a Wake-On-LAN packet. MAC Address must match the NIC MAC, computer must have WOL enabled in the BIOS. Show Sample Output


    0
    wakeonlan 00:00:DE:AD:BE:EF
    tyzbit · 2014-06-13 16:16:33 1
  • Use this command to watch video files on the terminal using VLC. prerequisite: VLC and cvlc sudo apt-get install vlc cvlc Show Sample Output


    0
    cvlc /path/to/file.avi -V caca
    tyzbit · 2014-06-13 16:10:36 6

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Propagate X session cookies on a different user and login as that user
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View Processeses like a fu, fu
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Find usb device in realtime
Using this command you can track a moment when usb device was attached.

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

Double your disk read performance in a single command
(WARN) This will absolutely not work on all systems, unless you're running large, high speed, hardware RAID arrays. For example, systems using Dell PERC 5/i SAS/SATA arrays. If you have a hardware RAID array, try it. It certainly wont hurt. You may be can test the speed disk with some large file in your system, before and after using this: $ time dd if=/tmp/disk.iso of=/dev/null bs=256k To know the value of block device parameter known as readahead. $ blockdev --getra /dev/sdb And set the a value 1024, 2048, 4096, 8192, and maybe 16384... it really depends on the number of hard disks, their speed, your RAID controller, etc. (see sample)

Define a quick calculator function
POSIX compliant arithmetic evaluation. = 10*2+3

Bind a key with a command
Now type Ctrl-l and it will list all files

Ping all hosts on 192.168.1.0/24
Will report back IP address's of all hosts that are UP.

Find the package that installed a command

find which lines in a file are longer than N characters
Filter out lines of input that contain 72, or fewer, characters. This uses bash only. ${#i} is the number of characters in variable i.


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