Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

#include <stdio.h>
#include <string.h>

int main(void)
{
    char  src[] = "Hello, World";
    char  dest[64];
    char  upper[64];

/* strlen does NOT count the null terminator */
    printf("strlen(\"%s\") = %zu
", src, strlen(src));   /* 12 */

/* strcpy: destination must be large enough */
    strcpy(dest, src);
    printf("strcpy: \"%s\"
", dest);

/* strncpy: safer — limits bytes copied */
    strncpy(upper, src, sizeof(upper) - 1);
    upper[sizeof(upper) - 1] = '\0';   /* always null-terminate! */

/* strcmp: 0 means equal */
    printf("strcmp same:     %d
", strcmp(src, dest));    /* 0  */
    printf("strcmp 'a','b':  %d
", strcmp("a", "b"));    /* <0 */

/* strcat: appending */
    char greeting[64] = "Hello";
    strncat(greeting, ", C!", sizeof(greeting) - strlen(greeting) - 1);
    printf("strcat: \"%s\"
", greeting);

/* strchr: find first occurrence of character */
    char *comma = strchr(src, ',');
    if (comma)
        printf("Found ',' at position %td
", comma - src);

/* strstr: find substring */
    char *world = strstr(src, "World");
    if (world)
        printf("Found \"World\" at position %td
", world - src);

/* Manually uppercase using pointer walk */
    char *p = upper;
    while (*p) {
        if (*p >= 'a' && *p <= 'z') *p -= 32;
        p++;
    }
    printf("upper: \"%s\"
", upper);

return 0;
}