I'm looking to write a pair of utilities that read in a newline separated list of integers on stdin and output their binary (4 byte) equivalent to stdout, and vice versa.
My first thought was a simple bash/linux command that would do this, but I was unable to find one. My second thought was to do this in C++, but I can't figure out how to change stdin or stdout to a binary stream.
Any thoughts on a good way to do this? I'm impartial to any particular programming language.
In Perl, you could just try:
perl -ne 'chomp; print pack 'i', $_;'
That will give you a host native signed integer of at least 32 bits, but possibly more depending on your local C compiler.
Other options to pack can go in place of the 'i', such as 'l' which will give you a signed long, which should be 32-bits. And there yet more options for little-endian or big-endian.
For the full description, please see http://perldoc.perl.org/functions/pack.html.
And here's your solution in C, in case you want to do it the boring way. :)
#include <stdio.h>
int main () {
int x;
while (fscanf(stdin, "%i", &x)) {
fwrite(&x, sizeof(x), 1, stdout);
}
return 0;
}
You don't need to "change stdout to binary", just output binary to it. This will certainly confuse e.g. a terminal emulator connected to that stream, but that is to be expected.
A plain loop of fscanf() to read each integer, followed by a fwrite() to write it out should work. Beware of endianness issues though, you might want to output each byte separately.
On Unix and its derivatives, there is no need to be concerned about whether the stdin or stdout are 'binary' mode - binary and text modes are the same. I've not conducted extensive testing on Windows, but under Cygwin, I've not noticed any issues there, either.
fwrite() should be used instead.