Commands using od (28)

  • Add Rudimentary Logging Levels According to STDOUT/STDERR

    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
  • Random unsigned integer

    Grab 4 bytes from www.random.org over ssl and format them as an integer


    -1
    curl -s "https://www.random.org/cgi-bin/randbyte?nbytes=4" | od -DAn
    PhillipNordwall · 2010-11-09 18:26:24 0
  • Generat a Random MAC address


    -1
    2>/dev/null dd if=/dev/urandom bs=1 count=6 | od -t x1 |sed '2d;s/^0\+ //;s/ /:/g'
    flyc0r · 2011-05-17 21:04:35 0
  •  < 1 2

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Easily scp a file back to the host you're connecting from
Place in .bashrc and invoke like this: "mecp /path/to/file", and it will copy the specified file(s) back to the desktop of the host you're ssh'ing in from. To easily upload a file from the host you're ssh'ing in from use this: ucp (){ scp ${SSH_CLIENT%% *}:Desktop/upload/* .; }

create an emergency swapfile when the existing swap space is getting tight
Create a temporary file that acts as swap space. In this example it's a 1GB file at the root of the file system. This additional capacity is added to the existing swap space.

cut audio file

Write on the console without being registered
just use a space to prevent commands from being recorded in bash's history on most systems

Use result of the last command
\$ which python /usr/bin/python \$ ll `!!` lrwxrwxrwx 1 root root 9 2010-11-08 22:01 /usr/bin/python -> python2.6

umount --rbind mount with submounts
Original: https://bugzilla.redhat.com/show_bug.cgi?id=194342

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"

Virtual Console lock program
vlock command locks the current console by default. Also you can lock all the consoles on the server by using -a parameter. For details, pl man vlock. ps: Generally speaking , system will not install vlock programme . So you should use ' $ sudo apt-get install vlock ' to install vlock .

Search for an active process without catching the search-process
This does the same thing as many of the 'grep' based alternatives but allows a more finite control over the output. For example if you only wanted the process ID you could change the command: $ ps -ef | awk '/mingetty/ && !/awk/ {print $2}' If you wanted to kill the returned PID's: $ ps -ef | awk '/mingetty/ && !/awk/ {print $2}' | xargs -i kill {}

search string in _all_ revisions

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