stdlib.h

stdlib.h: C Standard General Utilities Library

This header defines several general purpose functions, including dynamic memory management, random number generation, communication with the environment, integer arithmetics, searching, sorting and converting.

String Conversion

Searching and Sorting

qsort

void qsort (void* base, size_t num, size_t size, int (*compar)(const void*,const void*));

Sorts the num elements of the array pointed to by base, each element size bytes long, using the compar function to determine the order.

An example of compar function:

int compare (const void * a, const void * b) {
  return ( *(int*)a - *(int*)b );
}

Random

rand

#include <stdlib.h>
#include <time.h>

srand(time(NULL));
int i = rand() % 10;  // i \in [0, 9]

Dynamic Memory Management