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May 19, 2015 - A Look At The New Commandlinefu
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extracts 64 bytes of random digits from random lines out of /dev/random sent to stdio

Terminal - extracts 64 bytes of random digits from random lines out of /dev/random sent to stdio
cat /dev/urandom|od -t x1|awk 'NR > line { pos=int(rand()*15)+2;printf("%s",$pos);line=NR+(rand()*1000);digits = digits+2 } digits == 64 { print("\n");exit }'
2012-08-14 19:02:00
User: jetdillo
Functions: awk cat exit od
extracts 64 bytes of random digits from random lines out of /dev/random sent to stdio

Use this the next time you need to come up with a reasonably random bitstring, like for a WPA/WPA2 PSK or something. Takes a continuous stream of bytes coming from /dev/urandom, runs it through od(1), picking a random field ($0 and $1 excluded) from a random line and then prints it.


There are 6 alternatives - vote for the best!

Terminal - Alternatives

Know a better way?

If you can do better, submit your command here.

What others think

Your command can be shortened quite a bit.

First, picking random digits out of a random stream doesn't make the result any more random

(ask a mathematician for a fuller explanation).

Next, ask pass /dev/urandom to od directly:

od -t x1 /dev/urandom | ...

Finally replace awk with an incomprehensible sed :-)

od -t x1 /dev/urandom | sed '$!N;s/\n//;s/\([0-9]\{7\}\)\| //g;2q'

Which means: Join the first two lines


Strip out blocks of 7 digits, or single spaces

s/\([0-9]\{7\}\)\| //g

Stop processing after two lines of input:

Comment by flatcap 296 weeks and 2 days ago

You can do this just using hexdump. To get 80 bytes of pseudo-random hex:

hexdump -n 80 -e '80/1 "%x" "\n"' /dev/urandom

-n 80 limits the input to 80 bytes. -e takes the hexdump format string:

80/1 "%x" "\n"

80/1 tells hexdump to apply the following format string (%x for hex) 80 times one byte at a time. Then it prints the new line.

Comment by my_username 171 weeks and 4 days ago

Small omission in my previous example. You need to specify 0 padding in the format string:

hexdump -n 80 -e '80/1 "%02x" "\n"' /dev/urandom
Comment by my_username 171 weeks and 4 days ago

Your point of view

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