Returns the hyperbolic arc tangent of its argument.

Format

#include <math.h>

double atanh (double x);

float atanhf (float x);

long double atanhl (long double x);

Argument

x

A radian expressed as a real value in the domain [-1, 1].

Description

The atanh functions return the hyperbolic arc tangent of x. The atanh function is the inverse function of tanh where atanh ( tanh (x)) = x.

|x| > 1 is an invalid argument.

Registers a function that is called without arguments at program termination.

Format

#include <stdlib.h>

int atexit (void (*func) (void));

Argument

func

A pointer to the function to be registered.

Return Values

0	Indicates that the registration has succeeded.
nonzero	Indicates failure.

Restriction

The longjmp function cannot be executed from within the handler, because the destination address of the longjmp no longer exists.

Example

#include <stdlib.h> #include <stdio.h> static void hw(void); main() { atexit(hw); } static void hw() { puts("Hello, world\n"); }

Running this example produces the following output:

Hello, world

Converts an ASCII character string to a double-precision number.

Format

#include <stdlib.h>

double atof (const char *nptr);

Argument

nptr

A pointer to the character string to be converted to a double-precision number. The string is interpreted by the same rules that are used to interpret floating constants.

Description

The string to be converted has the following format:

[white-spaces][+|-]digits[radix-character][digits][e|E[+|-]integer]

Where radix-character is defined in the current locale.

The first unrecognized character ends the conversion.

This function is equivalent to strtod(nptr, (char**) NULL) .

Return Values

x	The converted value.
0	Indicates an underflow or the conversion could not be performed. The function sets errno to ERANGE or EINVAL, respectively.
(+/-)HUGE_VAL	Indicates overflow; errno is set to ERANGE.

Convert strings of ASCII characters to the appropriate numeric values.

Format

#include <stdlib.h>

int atoi (const char *nptr);

long int atol (const char *nptr);

Argument

nptr

A pointer to the character string to be converted to a numeric value.

Description

The atoi and atol functions convert the initial portion of a string to its decimal int or long int value, respectively. The atoi and atol functions do not account for overflows resulting from the conversion. The string to be converted has the following format:

[white-spaces][+|-]digits

The function call atol (str) is equivalent to strtol (str, (char**)NULL, 10) , and the function call atoi (str) is equivalent to (int) strtol (str, (char**)NULL, 10) , except, in both cases, for the behavior on error.

Return Value

n	The converted value.

Convert strings of ASCII characters to the appropriate numeric values. atoll is a synonym for atoq .

Format

#include <stdlib.h>

__int64 atoq (const char *nptr);

__int64 atoll (const char *nptr);

Argument

nptr

A pointer to the character string to be converted to a numeric value.

Description

The atoq (or atoll ) function converts the initial portion of a string to its decimal __int64 value. This function does not account for overflows resulting from the conversion. The string to be converted has the following format:

[white-spaces][+|-]digits

The function call atoq (str) is equivalent to strtoq (str, (char**)NULL, 10) , except for the behavior on error.

Return Value

n	The converted value.

Returns the last component of a path name.

Format

#include <libgen.h>

char *basename (char *path);

Argument

path

A UNIX style pathname from which the base path name is extracted.

Description

This function takes the UNIX style pathname pointed to by path and returns a pointer to the pathname's final component, deleting any trailing slash (/) characters.

If path consists entirely of the slash (/) character, the function returns a pointer to the string "/".

If path is a NULL pointer or points to an empty string, the function returns a pointer to the string ".".

The basename function can modify the string pointed to by path.

Return Values

x	A pointer to the final component of path.
"/"	If path consists entirely of the '/' character.
"."	If path is a NULL pointer or points to an empty string.

Compares byte strings.

Format

#include <strings.h>

void bcmp (const void *string1, const void *string2, size_t length);

Arguments

string1, string2

The byte strings to be compared.

length

The length (in bytes) of the strings.

Description

The bcmp function compares the byte string in string1 against the byte string in string2.

Unlike the string functions, there is no checking for null bytes. Zero-length strings are always identical.

Note that bcmp is equivalent to memcmp , which is defined by the ANSI C Standard. Therefore, using memcmp is recommended for portable programs.

Return Values

0	The strings are identical.
Nonzero	The strings are not identical.

Copies byte strings.

Format

#include <strings.h>

void bcopy (const void *source, void *destination, size_t length);

Arguments

source

Pointer to the source string.

destination

Pointer to the destination string.

length

The length (in bytes) of the string.

Description

The bcopy function operates on variable-length strings of bytes. It copies the value of the length argument in bytes from the string in the source argument to the string in the destination argument.

Unlike the string functions, there is no checking for null bytes. If the length argument is 0 (zero), no bytes are copied.

Note that bcopy is equivalent to memcpy , which is defined by the ANSI C Standard. Therefore, using memcpy is recommended for portable programs.

Draws a box around the window using the character vert as the character for drawing the vertical lines of the rectangle, and hor for drawing the horizontal lines of the rectangle.

Format

#include <curses.h>

int box (WINDOW *win, char vert, char hor);

Arguments

win

The address of the window.

vert

The character for the vertical edges of the window.

hor

The character for the horizontal edges of the window.

Description

This function copies boxes drawn on subwindows onto the underlying window. Use caution when using functions such as overlay and overwrite with boxed subwindows. Such functions copy the box onto the underlying window.

Return Values

OK	Indicates success.
ERR	Indicates an error.

Determines the lowest virtual address that is not used with the program.

Format

#include <stdlib.h>

void *brk (unsigned long int addr);

Argument

addr

The lowest address, which the function rounds up to the next multiple of the page size. This rounded address is called the break address.

Description

An address that is greater than or equal to the break address and less than the stack pointer is considered to be outside the program's address space. Attempts to reference it will cause access violations.

When a program is executed, the break address is set to the highest location defined by the program and data storage areas. Consequently, brk is needed only by programs that have growing data areas.

Return Values

n	The new break address.
(void *)(--1)	Indicates that the program is requesting too much memory. errno and vaxc$errno are updated.

Restriction

Unlike other C library implementations, the Compaq C RTL memory allocation functions (such as malloc ) do not rely on brk or sbrk to manage the program heap space. Consequently, on OpenVMS systems, calling brk or sbrk can interfere with memory allocation routines. The brk and sbrk functions are provided only for compatibility purposes.

Performs a binary search. It searches an array of sorted objects for a specified object.

Format

#include <stdlib.h>

void *bsearch (const void *key, const void *base, size_t nmemb, size_t size, int (*compar)
(const void *, const void *));

Arguments

key

A pointer to the object to be sought in the array. This pointer should be of type pointer-to-object and cast to type pointer-to-void.

base

A pointer to the initial member of the array. This pointer should be of type pointer-to-object and cast to type pointer-to-void.

nmemb

The number of objects in the array.

size

The size of an object, in bytes.

compar

A pointer to the comparison function.

Description

The array must first be sorted in increasing order according to the specified comparison function pointed to by compar.

Two arguments are passed to the comparison function pointed to by compar. The two arguments point to the objects being compared. Depending on whether the first argument is less than, equal to, or greater than the second argument, the comparison function must return an integer less than, equal to, or greater than 0.

It is not necessary for the comparison function (compar) to compare every byte in the array. Therefore, the objects in the array can contain arbitrary data in addition to the data being compared.

Since it is declared as type pointer-to-void, the value returned must be cast or assigned into type pointer-to-object.

Return Values

x	A pointer to the matching member of the array or a null pointer if no match is found.
NULL	Indicates that the key cannot be found in the array.

Example

#include <stdio.h> #include <stdlib.h> #define SSIZE 30 extern int compare(); /* prototype for comparison function */ int array[SSIZE] = {30, 1, 29, 2, 28, 3, 27, 4, 26, 5, 24, 6, 23, 7, 22, 8, 21, 9, 20, 10, 19, 11, 18, 12, 17, 13, 16, 14, 15, 25}; /* This program takes an unsorted array, sorts it using qsort, */ /* and then calls bsearch for each element in the array, */ /* making sure that bsearch returns the correct element. */ main() { int i; int failure = FALSE; int *rkey; qsort(array, SSIZE, sizeof (array[0]), &compare); /* search for each element */ for (i = 0; i < SSIZE - 1; i++) { /* search array element i */ rkey = bsearch((array + i), array, SSIZE, sizeof(array[0]), &compare); /* check for successful search */ if (&array[i] != rkey) { printf("Not in array, array element %d\n", i); failure = TRUE; break; } } if (!failure) printf("All elements successfully found!\n"); } /* Simple comparison routine. */ /* */ /* Returns: = 0 if a == b */ /* < 0 if a < b */ /* > 0 if a > b */ int compare(int *a, int *b) { return (*a - *b); }

This example program outputs the following:

All elements successfully found!

Converts a one-byte multibyte character to a wide character in the initial shift state.

Format

#include <wchar.h>

wint_t btowc (int c);

Arguments

c

The character to be converted to a wide-character representation.

Description

This function determines whether ( unsigned char )c is a valid one-byte multibyte character in the initial shift state, and if so, returns a wide-character representation of that character.

Return Values

x	The wide-character representation of unsigned char c .
WEOF	Indicates an error. The c argument has the value EOF or does not constitute a valid one-byte multibyte character in the initial shift state.

Copies null characters into byte strings.

Format

#include <strings.h>

void bzero (void *string, size_t length);

Arguments

string

Specifies the byte string into which you want to copy null characters.

length

Specifies the length (in bytes) of the string.

Description

This function copies null characters ('\0') into the byte string pointed to by string for length bytes. If length is 0 (zero), then no bytes are copied.

Returns the absolute value of a complex number.

Format

#include <math.h>

double cabs (cabs_t z);

float cabsf (cabsf_t z); (ALPHA ONLY)

long double cabsl (cabsl_t z); (ALPHA ONLY)

Arguments

z

A structure of type cabs_t , cabsf_t , or cabsl_t . These types are defined in the <math.h> header file as follows:

typedef struct {double x,y;} cabs_t; typedef struct { float x, y; } cabsf_t; (ALPHA ONLY) typedef struct { long double x, y; } cabsl_t; (ALPHA ONLY)

Description

The cabs functions return the absolute value of a complex number by computing the Euclidean distance between its two points as the square root of their respective squares:

sqrt(x2 + y2)

On overflow, the return value is undefined.

The cabs , cabsf , and cabsl functions are equivalent to the hypot , hypotf , and hypotl functions, respectively.

Allocates an area of zeroed memory. This function is AST-reentrant.

Format

#include <stdlib.h>

void *calloc (size_t number, size_t size);

Arguments

number

The number of items to be allocated.

size

The size of each item.

Description

The calloc function initializes the items to 0.

See also malloc and realloc in this section.

Return Values

n	The address of the first byte, which is aligned on a quadword boundary.
NULL	Indicates an inability to allocate the space.