Thread: Help adding leading zero's to a char!!

Hi all;

I basically want to add leading zero's to a char when going from int to a char in snprintf.

See example :

Code:

unsigned char len[2];
int length = 144;

snprintf(len, 2, "02%d", length);  /*this would add leading zeros to the integer*/

snprintf(len, 2, "02%c", length);  /*this doesnt work for a char, any ideas?

Thanks

First off, the correct format string to add leading zeroes to an integer is "%02d". Note that with your example (but with the corrected format string), since you are passing in 2 as the size of the buffer, the string will contain "1", which is one character plus a null terminator.

Second, what does it mean to add leading zeroes to a char? "%c" gives you a single character. If you want a leading zero in front of that, use "0%c". But again, "%c" is just a character, not a decimal integer or anything like that. For example, if you tried to print "0%c" to a string with the character 65, you would get the string "0A" (but by passing a size of 2 to snprintf, the string would always be "0"). Is that what you want? If not you need to be more specific about what you actually want to do.

Thanks for the replies .

Basically my unsigned char array will hold 0x00 0x00
if value is 144 Dec i like it to be 0090 in array in hex. so maybe i should use %x in sprintf?

thks

Try reading this page.

Do you want a 16-bit big-endian binary value stored in your array?

Code:

sprintf(len, "%c%c", 0, length); // note: this is only one way to do this

Or do you want a human-readable string like "0090"? That requires 5 bytes in your array (or 4 if you don't have a null terminator), plus reading the page that whiteflags linked to.