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 59
  • 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 28
  • 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.commandlinefu.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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Selecting a random file/folder of a folder
Also looks in subfolders

Smart renaming
A powerfull way to rename file using sed groups. & stand for the matched expression. \1 referes to the first group between parenthesis. \2 to the second.

Time Synchronisation with NTP

Get just the IP for a hostname
has the benefit of being a bit more cross-platform.

Find broken symlinks and delete them
recursively deletes all broken symlinks using zsh globbing syntax.

Get ethX mac addresses
I much prefer using /sbin/ip over /sbin/ifconfig for most everything. I find the interface and output to be much more consistent and it has many abilities that ifconfig, route, etc. do not. To get the mac address for only one interface, add 'show dev [interface]' to the 'ip link' part of the command: ip link show dev eth0 | grep 'link/ether' | awk '{print $2}' . Also, both this command and the ifconfig one do not require root access to run, so the sudo is not necessary.

list block devices
Shows all block devices in a tree with descruptions of what they are.

Encrypt every file in the current directory with 256-bit AES, retaining the original.
The password is stored in the password file, which obviously must be kept secure, encrypted later with gpg, deleted, or whatever you prefer. To decrypt: $ openssl enc -d -aes-256-cbc -salt -in filename.enc -out filename -pass file:/path/to/password-file Alternative ciphers can be used, of course.

Get lines count of a list of files
This command gives you the number of lines of every file in the folder and its subfolders matching the search options specified in the find command. It also gives the total amount of lines of these files. The combination of print0 and files0-from options makes the whole command simple and efficient.

Shows all packages installed that are recommended by other packages
Shows the packages installed on your system that are recomemnded by other packages. You should remove these packages.


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