是否可以使用 bash sript 将数字的二进制表示形式写入文件？

Question

I need to write the 4 bytes representation of a number (176) into a .bin file. I was using the following command

perl -we 'print pack "N", shift' 176 >> package.bin

and it works fine. But now I'd need to do exactly the same thing without using perl. Is it possible? I can only find solutions with perl but unfortunatly I can't use it because of project requirements.

I also tried this solution:

local n bit
for (( n=$1 ; n>0 ; n >>= 1 )); do  bit="$(( n&1 ))$bit"; done
echo -n -e $bit > tobin.bin

But it doesn't work because it writes 10110000 into my destination file and it is wrong because it is considered to be 8 bytes long and not 4 (1 byte for each character).

Answer 1

Try

num=176

printf -v oct0 '%03o' "$(( (num>>24) & 0xff ))"
printf -v oct1 '%03o' "$(( (num>>16) & 0xff ))"
printf -v oct2 '%03o' "$(( (num>> 8) & 0xff ))"
printf -v oct3 '%03o' "$(( num       & 0xff ))"

printf "\\$oct0\\$oct1\\$oct2\\$oct3" >package.bin

• You can set num to any 32-bit positive integer value.
• See BashFAQ/071 (How do I convert an ASCII character to its decimal (or hexadecimal) value and back?) for details of how the conversion is done.