Converting strings to uppercase to compare with user input in C - c

Question

I am attempting to create a program that will allow a user to search for a name in a file. The program does this successfully, but then it occurred to me that not everyone will type in the name as it is capitalized in the file. That is, someone may search for "sarah," but as the name is listed as "Sarah" in the file the name will not be found. To get around this I have attempted to convert both strings into upper case at the time of comparison. I am very, very new to teaching myself C, so I am not certain if I am even heading in the right direction. At this point I cannot even get the program to compile as I am getting two errors that say "array initializer must be an initializer list or string literal." I'm assuming that to mean that my syntax is not only invalid but completely in the wrong direction. What would be the best way to approach my goal?
#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main(void)
{
FILE *inFile;
inFile = fopen("workroster.txt", "r");
char rank[4], gname[20], bname[20], name[20];
printf("Enter a name: __");
scanf("%s", name);
int found = 0;
while(fscanf(inFile, "%s %s %s", rank, bname, gname)== 3)
{ char uppername[40] = toupper(name[15]);
char upperbname[40] = toupper(bname[15]);
if(strcmp(uppberbname,uppername) == 0)
{
printf("%s is number %s on the roster\n", name, rank);
found = 1;
}
}
if ( !found )
printf("%s is not on the roster\n", name);
return 0;
}

Answer 1

This two lines are wrong:
char uppername[40] = toupper(name[15]);
char upperbname[40] = toupper(bname[15]);
int toupper(int c); takes an int and returns an int
Because in C string is just an array of chars with a null terminator, so what you can do is to convert each character of the string to uppercase:
for (size_t I = 0; I < strlen(name); I++) {
uppername[I] = toupper(name[I]);
}
uppername[I] = '\0';
Regarding compare, you can use strcasecmp as suggested, which is Posix.
If you want to just use function in the C stdlib, convert the string as above, and then use strcmp.

Answer 2

toupper() works on a single character, not on a string.
No need to convert the input strings. Simple call a string case-insensitive compare.
As C does not have a standard one, it is easy enough to create your own.
int mystricmp(const char *s1, const char *s2) {
// toupper works with unsigned char values.
// It has trouble (UB) with char, when char is signed.
const unsigned char *p1 = (const unsigned char *) s1;
const unsigned char *p2 = (const unsigned char *) s2;
while (toupper(*p1) == toupper(*p2) && *p1) {
p1++;
p2++;
}
int ch1 = toupper(*p1);
int ch2 = toupper(*p1);
return (ch1 > ch2) - (ch1 < ch2);
}

Answer 3

use the following function, which is included in strings.h
int strcasecmp(const char *s1, const char *s2);
in your case change if statement
if(strcmp(uppberbname,uppername) == 0)
to
if(strcasecmp(bname,name) == 0)
and delete
char uppername[40] = toupper(name[15]);
char upperbname[40] = toupper(bname[15]);

Answer 4

Because the function toupper is for converting a character from small to capital, you cannot use it for a string case conversion. But you can string using the same function in this way:
while(name[i])
{
uppername[i]=toupper(name[i]);
i++;
}
while(bname[j])
{
upperbname[j]=toupper(bname[j]);
j++;
}
These statements do our string case conversion. The whole Program:
#include <stdio.h>
#include <ctype.h>
#include <string.h>
int main(void) {
FILE *inFile;
inFile = fopen("workroster.txt", "r");
char rank[4], gname[20], bname[20], name[20], uppername[40], upperbname[40];
printf("Enter a name: __");
scanf("%s", name);
int found = 0, i = 0, j = 0;
while (fscanf(inFile, "%s %s %s", rank, bname, gname) == 3) {
while (name[i]) {
uppername[i] = toupper(name[i]);
i++;
}
while (bname[j]) {
upperbname[j] = toupper(bname[j]);
j++;
}
//char uppername[40] = toupper(name[15]);
//char upperbname[40] = toupper(bname[15]);
if (strcmp(uppername, upperbname) == 0) {
printf("%s is number %s on the roster\n", name, rank);
found = 1;
}
}
if (!found) printf("%s is not on the roster\n", name);
return 0;
}