Commands by kostis (4)

  • Quickly add a new user to all groups the default user is in

    This is a standard procedure for me, whenever I set up a new Raspberry Pi system. Because the default user is "pi", I quickly replace it with my own (e.g. "kostis"), but I have to substitute that user to all of pi's groups first, before deleting the default account. xargs helps a lot with that in a single line, while avoiding boring "for" loops. For everything trickier, there's always "parallel" :)


    3
    groups pi | xargs -n 1 | tail -n +4 | xargs -n 1 sudo adduser kostis
    kostis · 2022-01-25 07:20:09 574
  • Converts all pngs in a folder to webp using all available cores

    As an alternative to the above command, this one ditches the unnecessary and complicated for loop in favor of a way faster multi-core approach for a task that's more CPU than I/O intensive, making it a perfect suite for GNU parallel


    4
    parallel cwebp -q 80 {} -o {.}.webp ::: *.png
    kostis · 2018-12-07 23:37:24 34
  • quick integer CPU benchmark

    You could have that little benchmark run on all cores in parallel, as a multi-core benchmark or stress test First find the number of cores, then have parallel iterate over that in, well, parallel Show Sample Output


    -1
    time cat /proc/cpuinfo |grep proc|wc -l|xargs seq|parallel -N 0 echo "2^2^20" '|' bc
    kostis · 2018-12-06 05:36:55 1064
  • small CPU benchmark with PI, bc and time.

    Broken in two parts, first get the number of cores with cat /proc/cpuinfo |grep proc|wc -l and create a integer sequence with that number (xargs seq), then have GNU parallel loop that many times over the given command. Cheers! Show Sample Output


    -2
    time cat /proc/cpuinfo |grep proc|wc -l|xargs seq|parallel -N 0 echo "scale=4000\; a\(1\)\*4" '|' bc -l
    kostis · 2018-12-06 05:15:24 703

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Sort disk usage from directories
Sort disk usage from directories in the current directory

recursive search and replace old with new string, inside files
This command find all files in the current dir and subdirs, and replace all occurances of "oldstring" in every file with "newstring".

Wait for file to stop changing
This loop will finish if a file hasn't changed in the last 10 seconds. . It checks the file's modification timestamp against the clock. If 10 seconds have elapsed without any change to the file, then the loop ends. . This script will give a false positive if there's a 10 second delay between updates, e.g. due to network congestion . How does it work? 'date +%s' gives the current time in seconds 'stat -c %Y' gives the file's last modification time in seconds '$(( ))' is bash's way of doing maths '[ X -lt 10 ]' tests the result is Less Than 10 otherwise sleep for 1 second and repeat . Note: Clever as this script is, inotify is smarter.

get you public ip address

View a colorful logfile using less

bulk rename files with sed, one-liner
Far from my favorite, but works in sh and with an old sed that doesn't support '-E'

search office documents for credit card numbers and social security number SSN docx xlsx
# CC with SSN dash ( low false positive only match ###-##-#### not any 8digi number ) $ find . -iname "*.???x" -type f -exec unzip -p '{}' '*' \; | sed -e 's/]\{1,\}>/ /g; s/[^[:print:]]\{1,\}/ /g' | egrep "\b4[0-9]{12}(?:[0-9]{3})?\b|\b5[1-5][0-9]{14}\b|\b6011[0-9]{14}\b|\b3(?:0[0-5]\b|\b[68][0-9])[0-9]{11}\b|\b3[47][0-9]{13}\b|\b[0-9]{3}-[0-9]{2}-[0-9]{4}\b" $ rmccurdyDOTcom

List the size (in human readable form) of all sub folders from the current location

Run the last command as root
Useful when you forget to use sudo for a command. "!!" grabs the last run command.

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"

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