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Functions

Labyrinth pattern

Terminal - Labyrinth pattern
while ( true ) ; do if [ $(expr $RANDOM % 2 ) -eq 0 ] ; then echo -ne "\xE2\x95\xB1" ; else echo -ne "\xE2\x95\xB2" ; fi ; done
2015-01-17 12:46:37
User: tobi
Functions: echo expr true
2
Labyrinth pattern

Generates labyrinth-like pattern on UTF-8 terminal in bash.

For fun ;)

Alternatives

There are 3 alternatives - vote for the best!

Terminal - Alternatives
MAC=`(date; cat /proc/interrupts) | md5sum | sed -r 's/^(.{10}).*$/\1/; s/([0-9a-f]{2})/\1:/g; s/:$//;'`
2009-02-16 07:09:43
User: vaporub
Functions: cat md5sum sed
17

Original author unknown (I believe off of a wifi hacking forum).

Used in conjuction with ifconfig and cron.. can be handy (especially spoofing AP's)

openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/.$//'
2010-09-23 02:31:12
User: putnamhill
Functions: sed
Tags: sed xxd openssl
15

Use the following variation for FreeBSD:

openssl rand 6 | xxd -p | sed 's/\(..\)/\1:/g; s/:$//'
hexdump -n6 -e '/1 ":%02X"' /dev/random|sed s/^://g
2015-01-19 03:09:43
User: rubo77
Functions: hexdump sed
3

Generate a random MAC address with capital letters

od -An -N10 -x /dev/random | md5sum | sed -r 's/^(.{10}).*$/\1/; s/([0-9a-f]{2})/\1:/g; s/:$//;'
od /dev/urandom -w6 -tx1 -An|sed -e 's/ //' -e 's/ /:/g'|head -n 1
2011-05-16 15:05:34
User: karel1980
Functions: head od sed
2

Just increase the 1 at the end if you want to generate more than one.

(Alternative to "| head -n N" you could use the -b flag of od: -b $[6*N]

Know a better way?

If you can do better, submit your command here.

What others think

The output's pretty, but the command could be improved.

.

First, let's swap (true) for :

The colon operator is a null-operation (but it returns true).

So this is common:

while :; do COMMAND; done

.

Next, tidy the test condition and get rid of expr (an external command).

Bash supports doing maths in $((...))

if [ $(($RANDOM % 2)) -eq 0 ]; then ...

Personally, I'd change the "-eq 0" to "= 0"

Yes, that's a string comparison, but it's nicer to read.

.

Next, replace the if statement with some boolean operators.

'[' is a command in its own right: man test(1)

If you've only got two one-command options, you can write:

[ TEST-CONDITION ] && TRUE-COMMAND || FALSE-COMMAND

.

Combine all the above and you get:

while :; do [ $(($RANDOM % 2)) = 0 ] && echo -ne "\xE2\x95\xB1" || echo -ne "\xE2\x95\xB2"; done

.

Because it only uses bash builtin commands it's much quicker, too.

Comment by flatcap 152 weeks and 2 days ago

Hmm... I wasn't content with my previous answer.

It's not 'fu' enough :-)

The output is one of:

echo -ne "\xE2\x95\xB1" echo -ne "\xE2\x95\xB2"

.

So I need to substitute a 1 or a 2 into an echo.

.

Adding 1 to the previous random number:

echo $((RANDOM%2+1))

.

And substitute for the test condition:

while :; do echo -ne "\xE2\x95\xB$((RANDOM%2+1))"; done

.

Much nicer.

Comment by flatcap 152 weeks and 2 days ago

Well, really fast!

Comment by tobi 152 weeks and 2 days ago

Your point of view

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