C Transforming array into string using sprintf - c

Question

I have scanned "ABCDEFGHIJK" with fscanf into a char array[26]. Then I got "ABCDEFGHIJK" using "for" into another array[11]. Now I need to get to an "ABCDEFGHIJK.mp4" array[15] in order to feed that filename into a rename function.
I don't know much about C programming besides printf, scanf, for and while.
sprintf(filename, "%c%c%c%c%c%c%c%c%c%c%c.mp4", codigo[0], codigo[1], codigo[2], codigo[3], codigo[4], codigo[5], codigo[6], codigo[7], codigo[8], codigo[9], codigo[10]);
This code above seems to work, but I wonder if there is a simpler way (especially for bigger arrays)?
Clarification: I have a txt file, formatted with these containing the filenames without extension and the human filename. I'm trying to make a program that will rename these files to the correct name, as they are from a backup that failed.
EDIT: Here is the full program. I renamed the variables to make more sense, so "codigo" is now "idcode".
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(void)
{
int i, j, k;
char value1[26], value2[70], idcode[11], filename[16], fullname[64], filenamestring[16], fullnamestring[64];
// Opening file.
FILE *nomes;
nomes = fopen("/Users/EA/Desktop/Songs/backup.txt", "rt");
if(nomes == NULL)
{
printf("Erro ao abrir backup.txt");
exit(1);
}
// Skipping beggining of file until first value.
for(i=0; i<10; i++)
{
fscanf(nomes, "%*s");
}
// Reading first value, and repetition.
while(fscanf(nomes, "%s", value1) == 1)
{
j = k = 0;
// Extracting idcode from value1.
for(i=7; i<18; i++)
{
idcode[j] = value1[i];
j++;
}
// Filling the complete filename.
sprintf(filename, "%.*s.mp4", 11, idcode);
// Reading second value, the "human" filename.
fscanf(nomes, "\n%[^\n]", value2);
for(i=6; i<70; i++)
{
fullname[k] = value2[i];
k++;
}
// Transforming filenames into strings for rename function.
strncpy(filenamestring, filename, 16);
strncpy(fullnamestring, fullname, 64);
// Renaming the files.
rename(filename, fullname);
// Skipping useless data before the next cycle.
for(i=0; i<9; i++)
{
fscanf(nomes, "%*s");
}
}
// Closing file and ending program.
fclose(nomes);
return(0);
}

Answer 1

It looks like you got an array of char's.
You can simply do:
sprintf(filename, "%.*s.mp4", 11, codigo)
You can read more about the %.*s specifier in this question.

Answer 2

If you just want to append the format ".mp4" to the end of the string the easiest way to do that is just:
strcat(filename,".mp4");
after you printed the name without the ".mp4" into it.
If you really want to use sprintf then i think this should suffice:
sprintf(filename,"%s.mp4", codigo);
Also,if you want your string to be bigger and not fixed in size you can put "\0" at the end of it(this might not work if you try to use the strings in other programming languages but c) with strcat as above,or you can do this:
memset(&filename, 0, sizeof(filename));