I need to count how many bits are set in a binary file. I considered processing the strings from an "od -x" output, since that would remove the many consecutive zero bytes I expect, but I also took a whack with this: 
perl -e '$bytes= -s "dwtest.dat"; 
open(FIN,"dwtest.dat") or die "cant open file\n"; 
$sum=0; 
for($i=0;$i<$bytes;$i++){ 
read(FIN,$c,1); 
(($c | 0x01) && ($sum++)); 
(($c | 0x02) && ($sum++)); 
(($c | 0x04) && ($sum++)); 
(($c | 0x08) && ($sum++)); 
(($c | 0x10) && ($sum++)); 
(($c | 0x20) && ($sum++)); 
(($c | 0x40) && ($sum++)); 

(($c | 0x80) && ($sum++)); 
} 
print "$sum bits are set\n";'

[download]
It works, but it's slow.

Does anyone have a faster solution?

update
pg is right, I'm a bonehead, a bitwise and on the ord is needed. I'm dealing with either 512MB or 4GB files. When I'm working with 512M, Randal's code flies, but because of the slurp, I think I'll have to go to jmcnamara's when I deal with 4G. Now I'm looking at minutes, rather than hours - thanks!

In reply to counting set bits in binary file by dwhite20899

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