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 }'
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.
Sample Output
afca515ee00c0c92637ee8d7a476f8a380b969cc43e205bb086e622f2b77ebdd

1
By: jetdillo
2012-08-14 19:02:00

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 $!N;s/\n// Strip out blocks of 7 digits, or single spaces s/\([0-9]\{7\}\)\| //g Stop processing after two lines of input: 2q
flatcap · 321 weeks and 5 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.
my_username · 196 weeks and 6 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
my_username · 196 weeks and 6 days ago

What do you think?

Any thoughts on this command? Does it work on your machine? Can you do the same thing with only 14 characters?

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