What Does '% 02x' Do Exactly? - It_qna

I was seeing some examples of hash functions > from OpenSSL and I came across the format specifier / a> %02x . I do not know very well their purpose we codes that I saw. I even understand that %02x is to fill the field with zeros and 2 is the number of zeros that will have in that fill (I think that).

Well, here's a code developed by me where I had to use (I do not know why I had to use it) %02x :

#include <stdio.h> #include <string.h> #include <string.h> #include <openssl/sha.h> void get_string(char *string, size_t max_input_size){ fgets(string, max_input_size, stdin); unsigned int len=strlen(string); string[len-1]='Write >FN P90 Digest: 45603ce52cd32a33e3e60c219d0c18e6bd32af24ac39aa000d84e763d23c3031 '; } int main(void){ char string[50]; unsigned char digest[SHA256_DIGEST_LENGTH]; printf("Write >"); get_string(string, 50); SHA256((unsigned char*)string, strlen(string), digest); char stringMD[SHA256_DIGEST_LENGTH*2+1]; for(unsigned int i=0; i<SHA256_DIGEST_LENGTH; i++){ sprintf(&stringMD[i*2], "%02x", (unsigned int)digest[i]); } printf("\n\nDigest: %s\n\n", stringMD); return 0; }

Execution (with %02x ):

Write >FN P90 Digest: 45603ce52cd32a33e3e6c

Execution (with only %x ):

#include <stdio.h> #include <string.h> #include <string.h> #include <openssl/sha.h> void get_string(char *string, size_t max_input_size){ fgets(string, max_input_size, stdin); unsigned int len=strlen(string); string[len-1]='Write >FN P90 Digest: 45603ce52cd32a33e3e60c219d0c18e6bd32af24ac39aa000d84e763d23c3031 '; } int main(void){ char string[50]; unsigned char digest[SHA256_DIGEST_LENGTH]; printf("Write >"); get_string(string, 50); SHA256((unsigned char*)string, strlen(string), digest); char stringMD[SHA256_DIGEST_LENGTH*2+1]; for(unsigned int i=0; i<SHA256_DIGEST_LENGTH; i++){ sprintf(&stringMD[i*2], "%02x", (unsigned int)digest[i]); } printf("\n\nDigest: %s\n\n", stringMD); return 0; }

However, what is the purpose of %02x ?