Related Functions atof( ), atoi( ), and atoll( ) atoll in Software

Creation Quick Response Code in Software Related Functions atof( ), atoi( ), and atoll( ) atoll

#include <stdlibh> long long int atoll(const char *str);

atoll( ) was added by C99 The atoll( ) function converts the string pointed to by str into a long long int value It is otherwise similar to atoll( ) Related Functions atof( ), atoi( ), and atol( ) bsearch

#include <stdlibh> void *bsearch(const void *key, const void *buf, size_t num, size_t size, int (*compare)(const void *, const void *));

The bsearch( ) function performs a binary search on the sorted array pointed to by buf and returns a pointer to the first member that matches the key pointed to by key The number of elements in the array is specified by num, and the size (in bytes) of each element is described by size The function pointed to by compare is used to compare an element of the array with the key The form of the compare function must be as follows: int func_name(const void *arg1, const void *arg2);

It must return values as described in the following table: Comparison arg1 is less than arg2 arg1 is equal to arg2 arg1 is greater than arg2 Value Returned Less than zero Zero Greater than zero

The array must be sorted in ascending order with the lowest address containing the lowest element If the array does not contain the key, a null pointer is returned Example The following program reads a character entered at the keyboard and determines whether it belongs to the alphabet:

#include <stdlibh> #include <ctypeh> #include <stdioh> char *alpha = "abcdefghijklmnopqrstuvwxyz"; int comp(const void *ch, const void *s); int main(void) { char ch; char *p; printf("Enter a character: "); ch = getchar(); ch = tolower(ch); p = (char *) bsearch(&ch, alpha, 26, 1, comp); if(p) printf('' %c is in alphabet\n", *p); else printf("is not in alphabet\n"); return 0; } /* Compare two characters */ int comp(const void *ch, const void *s) {

Page 448 return *(char *)ch *(char *)s; }

#include <stdlibh> div_t div(int numerator, int denominator);

The div( ) function returns the quotient and the remainder of the operation numerator/denominator in a structure of type div_t The structure type div_t has these two fields:

int quot; /* quotient */ int rem; /* remainder */

This program displays the quotient and remainder of 10/3:

#include <stdlibh> #include <stdioh> int main(void) { div_t n; n = div(10, 3);

printf("Quotient and remainder: %d %d\n", nquot, nrem); return 0; }

#include <:stdlibh> void exit(int exit_code);

The exit( ) function causes immediate, normal termination of a program This means that termination functions registered by atexit( ) are called, and any open files are flushed and closed The value of exit_code is passed to the calling process usually the operating system if the environment supports it By convention, if the value of exit_code is zero, or EXIT_SUCCESS, normal program termination is assumed A nonzero value, or EXIT_FAILURE, is used to indicate an implementation-defined error Example This function performs menu selection for a mailing list program If Q is selected, the program is terminated

int menu(void) { char choice; do { printf(''Enter names (E)\n"); printf("Delete name (D)\n"); printf("Print (P)\n"); printf("Quit (Q)\n"); choice = getchar(); } while(!strchr("EDPQ", toupper(choice))); if(choice=='Q') exit(0); return choice; }

#include <stdlibh> void _Exit(int exit_code);

_Exit( ) was added by C99 The _Exit( ) function is similar to exit( ) except for the following: No calls to termination functions registered by atexit( ) are made No calls to signal handlers registered by signal( ) are made Open files are not necessarily flushed or closed Related Functions atexit( ), abort( ) and exit( ) getenv

#include <stdlibh> char *getenv(const char *name);

The getenv( ) function returns a pointer to environmental information associated with the string pointed to by name in the implementation-defined environmental information table The string must not be changed by your code The environment of a program may include such things as path names and devices online The exact nature of this data is implementation defined You will need to refer to your compiler's documentation for details If a call is made to getenv( ) with an argument that does not match any of the environment data, a null pointer is returned Example Assuming that a specific compiler maintains environmental information about the devices connected to the system, the following fragment returns a pointer to the list of devices:

Page 451 char *p /* (/ p = getevn(''DEVICES");