What is the complete list and best practices for string handling functions in C language?

Core String Functions:

String Length

c
size_t strlen(const char *str);
// Returns string length, excluding null terminator '\0'

String Copy

c
char *strcpy(char *dest, const char *src);
char *strncpy(char *dest, const char *src, size_t n);
// strncpy doesn't automatically add '\0', needs manual handling

String Concatenation

c
char *strcat(char *dest, const char *src);
char *strncat(char *dest, const char *src, size_t n);
// Ensure destination buffer is large enough

String Comparison

c
int strcmp(const char *s1, const char *s2);
int strncmp(const char *s1, const char *s2, size_t n);
// Return: 0 for equal, <0 if s1<s2, >0 if s1>s2

String Search

c
char *strchr(const char *str, int c);      // Find first occurrence
char *strrchr(const char *str, int c);     // Find last occurrence
char *strstr(const char *haystack, const char *needle);  // Find substring

String Tokenization

c
char *strtok(char *str, const char *delim);
// Note: strtok modifies original string and is not thread-safe

Secure Versions (C11)

c
errno_t strcpy_s(char *dest, rsize_t destsz, const char *src);
errno_t strcat_s(char *dest, rsize_t destsz, const char *src);

Best Practices:

Buffer Overflow Protection

c
// Unsafe
strcpy(dest, src);

// Safe approach
strncpy(dest, src, sizeof(dest) - 1);
dest[sizeof(dest) - 1] = '\0';

Safe String Concatenation

c
char buffer[100];
snprintf(buffer, sizeof(buffer), "%s%s", str1, str2);

Dynamic String Handling

c
char *safe_strdup(const char *str) {
    if (!str) return NULL;
    size_t len = strlen(str) + 1;
    char *copy = malloc(len);
    if (copy) memcpy(copy, str, len);
    return copy;
}

String Formatting

c
char buffer[256];
int result = snprintf(buffer, sizeof(buffer), "Value: %d", value);
if (result < 0 || result >= sizeof(buffer)) {
    // Handle error
}

Common Pitfalls:

Forgetting to reserve space for '\0'
Using uninitialized strings
Confusing strlen with sizeof
Ignoring function return values
State issues with multiple strtok calls