C Library Functions

String Manipulation Functions

char *strcpy (char *dest, char *src);
Copy src string into dest string.

char *strncpy(char *string1, char *string2, int n);
Copy first n characters of string2 to stringl .

int strcmp(char *string1, char *string2);
Compare string1 and string2 to determine alphabetic order.

int strncmp(char *string1, char *string2, int n);
Compare first n characters of two strings.

int strlen(char *string);
Determine the length of a string.

char *strcat(char *dest, const char *src);
Concatenate string src to the string dest.

char *strncat(char *dest, const char *src, int n);
Concatenate n chracters from string src to the string dest.

char *strchr(char *string, int c);
Find first occurrence of character c in string.

char *strrchr(char *string, int c);
Find last occurrence of character c in string.

char *strstr(char *string2, char string*1);
Find first occurrence of string string1 in string2.

char *strtok(char *s, const char *delim) ;
Parse the string s into tokens using delim as delimiter.

Memory Management Functions

void *calloc(int num elems, int elem_size);
Allocate an array and initialise all elements to zero .

void free(void *mem address);
Free a block of memory.

void *malloc(int num bytes);
Allocate a block of memory.

void *realloc(void *mem address, int newsize);
Reallocate (adjust size) a block of memory.

Buffer Manipulation

void* memcpy(void* s, const void* ct, int n);
Copies n characters from ct to s and returns s. s may be corrupted if objects overlap.

int memcmp(const void* cs, const void* ct, int n);
Compares at most (the first) n characters of cs and ct, returning negative value if cs<ct, zero if cs==ct, positive value if cs>ct.

void* memchr(const void* cs, int c, int n);
Returns pointer to first occurrence of c in first n characters of cs, or NULL if not found.

void* memset(void* s, int c, int n);
Replaces each of the first n characters of s by c and returns s.

void* memmove(void* s, const void* ct, int n);
Copies n characters from ct to s and returns s. s will not be corrupted if objects overlap.

Character Functions

int isalnum(int c);
The function returns nonzero if c is alphanumeric

int isalpha(int c);
The function returns nonzero if c is alphabetic only

int iscntrl(int c);
The function returns nonzero if c is a control chracter

int isdigit(int c);
The function returns nonzero if c is a numeric digit

int isgraph(int c);
The function returns nonzero if c is any character for which either isalnum or ispunct returns nonzero.

int islower(int c);
The function returns nonzero if c is a lower case character.

int isprint(int c);
The function returns nonzero if c is space or a character for which isgraph returns nonzero.

int ispunct(int c);
The function returns nonzero if c is punctuation

int isspace(int c);
The function returns nonzero if c is space character

int isupper(int c);
The function returns nonzero if c is upper case character

int isxdigit(int c);
The function returns nonzero if c is hexa digit

int tolower(int c);
The function returns the corresponding lowercase letter if one exists and if isupper(c); otherwise, it returns c.

int toupper(int c);
The function returns the corresponding uppercase letter if one exists and if islower(c); otherwise, it returns c.

Error Handling Functions

void perror(const char *s);
produces a message on standard error output describing the last error encountered.

char *strerror(int errnum );
returns a string describing the error code passed in the argument errnum.

Leave a comment

Your email address will not be published.