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Shell Programming and Scripting

binary/hex output

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# 1  
Old 08-13-2008
binary/hex output
i want to output something like
2f 00 00 00

but i can't seem to escape characters like i'm used to in some programming languages, so with this:

echo "/\0\0\0" >> outputfile

i actually get
2f 5c 30 5c 30 5c 30 0a

ie the \0 isn't giving me the 00 i need, and in addition it has got an extra couple of bytes on the end - 0a (return carriage?).

obviously i'm going about this the wrong way - any suggestions? thanks.
# 2  
Old 08-13-2008
Code:
/home/jmcnama> printf "%c%c%c" 0 0 0 | od -c
0000000   0   0   0
0000003

does generate three ascii nul characters...
# 3  
Old 08-13-2008
Try without the quotes.

Code:
echo 2f \0\0 \0\0 \0\0
2f 00 00 00

# 4  
Old 08-15-2008
hm, without the quotes it still seems to just give the character values

2f 00 00 00

writes a file like this

32 66 20 30 30 20 30 30 20 30 30 0A

(32 for the '2' character, 66 for 'f', 20 for ' ' etc., and still with a return carriage at the end)

likewise with "%c" 0, this gives actual hex byte value of 30 (for an ascii '0' character)

any ideas how to get round this?
# 5  
Old 08-15-2008
How about echo -n /... | tr . '\000'

... or use Perl (or awk, or ...)

Code:
perl -e 'printf "/\0\0\0"'

# 6  
Old 08-15-2008
didn't know about -n, great thanks. what's the tr for? '.' seems to be 2e rather than 00
# 7  
Old 08-15-2008
the tr bit seems to do the trick but i dont get why.. thanks though
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