ANSI STANDARD C FUNCTION DEFINITIONS
FOR THE CURIOUS
THE DESPERATE
THE FRANTIC
AND THE SUICIDAL

Version 1.2.5

Updated 10 April 2005

The material contained in this ebook is not to be altered or copied without written permission from the author.
Geoffrey Trott ©1998
  t_geoffrey@hotmail.com
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A B C D E F G I L M O P Q R S T U V W
 
 
 
 

LIBRARIES

C89

assert.h    ctype.h    locale.h    math.h   setjmp.h     signal.h

  stdarg.h     stddef.h    stdio.h    stdlib.h     string.h    time.h   
   

C99

complex.h   ctype.h   fenv.h   inttypes.h   math.h    stdarg.h  

 stdio.h    stdlib.h    string.h    time.h    wchar.h   wctype.h  
 

abort

void abort (void)

HEADER      stdlib.h

PURPOSE
This function causes the program which calls it to end abruptly, unless SIGABRT is caught and the interrupt handler function defined by signal() does not return.

RESULT
No values are returned by this function.

NOTES
Whether files open when abort() is called are closed, or information contained within buffers linked to those files transferred, is implementation defined.
abort() calls raise(SIGABRT), which returns an implementation defined message confirming unsuccessful termination to the operating system.
Although ANSI does not require it, many implementations display an error message of some kind.

SEE ALSO  atexit(), exit().

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abs

int abs (int num)

HEADER      stdlib.h

PURPOSE
To convert the value passed to num into its absolute value.

RESULT
If successful abs() returns the absolute value of the integer num, otherwise the value returned is implementation defined.

NOTES
An absolute value can be any NON negative value including ZERO.

SEE ALSO   div(), fabs(), labs(), ldiv(), C99.

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acos

double acos (double angle)

HEADER      math.h

PURPOSE To convert the double precision value passed to angle into its arc cosine.

RESULT
If successful, acos() returns the arc cosine of angle in radians, otherwise if the value returned by acos() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, acos() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small acos() returns 0.0, but whether errno is set to ERANGE is implementation defined.

NOTES
If the value contained within angle is neither a double number, nor between -1 and 1.
A domain error (an illegal argument) will occur, the global integer errno set to EDOM, and an implementation defined value returned.

SEE ALSO   asin(), atan(), atan2(), cos(), cosh(), sin(), sinh(), tan(), tanh(), C99.

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asctime

char *asctime (const struct tm *currtime)

HEADER      time.h

PURPOSE
To obtain the current date, in the form of weekday, month, day of the month, hour, minutes, seconds, year.
This is then placed into a string 26 characters long.

RESULT
If successful, asctime() returns a pointer to the buffer where the character string has been stored,
otherwise the value it returns is implementation defined.

NOTES
Each time either asctime(), or ctime() is called, information stored within the string may be overwritten.
To initialise the tm structure pointed to by currtime, either localtime(), or gmtime() must be called.

The tm structure contains at least the following members in any order:

int tm_sec	the number of seconds	(0,60)
int tm_min	the number of minutes	(0,59)
int tm_hour	the number of hours	(0,23)
int tm_mday	the day of the month	(1,31)
int tm_month	the number of months since January	(0,11)
int tm_year	the number of years since 1900	(0,99)
int tm_wday	the number of days since Sunday	(0,6)
int tm_yday	the number of days since January 1st	(0,365)
int tm_isdst	the daylight savings time indicator

If the value of tm_isdst is GREATER than or EQUAL to 1, the daylight savings time indicator is switched on.
Or if the value of tm_isdst is ZERO then the indicator is switched off.
If the value of tm_isdst is negative the indicator is not being used.

SEE ALSO   clock(), difftime(), time().

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asin

double asin (double angle)

HEADER      math.h

PURPOSE
To convert the double precision value passed to angle into its arc sine.

RESULT
If successful, asin() returns the arc sine of angle, in radians, otherwise if the value returned by asin() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, asin() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small asin() returns 0.0, but whether errno is set to ERANGE is implementation defined.

NOTES
If the value contained within angle is neither a double number, nor between -1 and 1.
A domain error (a illegal argument) will occur, the global integer errno set to EDOM, and an implementation defined value returned.

SEE ALSO   acos(), atan(), atan2(), cos(), cosh(), sin(), sinh(), tan(), tanh(), C99.

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assert

void assert (int comparison)

HEADER      assert.h

PURPOSE
To help track down errors of logic within a program.

RESULT
No values are returned by this function.

NOTES
assert() is implemented as a macro not a function.
If the assert() macro is replaced by a function, the behavior of that function is undefined.
If the result of the comparison is ZERO, assert() generates an implementation defined error message.
Showing the predefined macros _FILE_ (the name of the file), and _LINE_ (the line where the error occurred),
together with the values contained within comparison.
Following this it calls abort().
Otherwise assert() will allow the program to continue.
If you wish to switch assert() off, after the program has been tested for bugs, #define the macro NDEBUG.

SEE ALSO   raise(), signal().

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atan

double atan (double angle)

HEADER      math.h

PURPOSE
To convert the double precision value passed to angle into its arc tangent.

RESULT
atan() returns the arc tangent of angle, in radians, otherwise if the value returned by atan() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, atan() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small atan() returns 0.0, but whether errno is set to ERANGE is implementation defined.

NOTES
If the value contained within angle is not a double value, a domain error (an illegal argument) will occur, the global integer errno set to EDOM, and an implementation defined value returned.

SEE ALSO   acos(), asin(), atan2(), cos(), cosh(), sin(), sinh(), tan(), tanh(), C99.

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atan2

double atan2 (double first, double second)

HEADER      math.h

PURPOSE
To calculate the value of the arc tangent of first divided by second, using the signs of both arguments to calculate its quadrant.

RESULT
If successful, atan2() returns the value of the arc tangent in radians, otherwise if the value returned by atan2() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, atan2() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small atan2() returns 0.0, but whether errno is set to ERANGE is implementation defined.

NOTES
If the values of both first and second do not contain double precision numbers, or contain ZERO.
A domain error (an illegal argument) will occur, the global integer errno set to EDOM, and an implementation defined value returned.

SEE ALSO   acos(), asin(), atan(), cos(), cosh(), sin(), sinh(), tan(), tanh(), C99.

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atexit

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

HEADER      stdlib.h

PURPOSE
The function pointed to by func(), will be called when the program terminates normally.

RESULT
atexit() returns ZERO if the function exists and can be nominated.
Otherwise a NON ZERO value is returned.

NOTES
ANSI allows a minimum of 32 termination functions to be nominated.
They are called in reverse order by exit(), these functions cannot have parameters.
 

SEE ALSO abort(), getenv(), system().

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atof

double atof (const char *string)

HEADER      stdlib.h

PURPOSE

To convert the character array pointed to by string into a double precision value.

RESULT
If successful, atof() returns a double value.
Otherwise its behavior is implementation defined, it does not have to change the value of the global integer errno.

NOTES
If *string does not contain a floating point number, the value returned cannot be used.
The character array must contain the following in this order:-
[WHITE SPACE SIGN] INTEGER DECIMAL POINT INTEGER [d,D,e,E SIGN INTEGER]
 

A WHITE SPACE consists of an optional space and or a tab character, which are both ignored.

SIGN is either + or -, and is also optional.

INTEGER may contain one or more decimal numbers.
 

If no numbers appear before the DECIMAL POINT then at least one must appear after it.
The numbers may be followed by an exponent, which consists of an introductory letter, either d, D, e, or E and an optional signed integer.
The character array will be processed by atof(), until the function reaches a character which it doesn't recognize, this includes `\0`.

SEE ALSO   atoi(), atol(), strtod(), strtol(), strtoul().

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atoi

int atoi (const char *string)

HEADER      stdlib.h

PURPOSE
To convert the contents of the character array, pointed to by string into an integer value.

RESULT
If successful, atoi() returns an integer value.
Otherwise its behavior is implementation defined, it does not have to change the value of the global integer errno.

NOTES
The character array pointed to by string must contain the following in this order:-
[WHITE SPACE SIGN] INTEGER
 

A WHITE SPACE consists of an optional space and or a tab character, which are both ignored.

SIGN is either + or -, and is also optional.

INTEGER may contain one or more decimal numbers.
 

The character array is processed by atoi() until the function reaches a character which it does not recognise , this includes `\0`.
atoi() does not recognise decimal points or exponents.

SEE ALSO   atof(), atol(), strtod(), strtol(), strtoul().

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atol

long int atol (const char *string)

HEADER      stdlib.h

PURPOSE
To convert the character array pointed to by string into a long integer.

RESULT
If atol() returns a long integer.
Otherwise its behavior is implementation defined, it does not have to change the value of the global integer errno.

NOTES
The character array pointed to by string must contain a long integer value, and take the form:-
[WHITE SPACE SIGN] LONG INTEGER
 

A WHITE SPACE consists of an optional space and or a tab character, which are both ignored.

SIGN is either + or -, and is also optional.

INTEGER may contain one or more decimal numbers.

The character array will then be processed by atol() until the function reaches a character which it doesn't recognise, this includes `\0`.
atol() does not recognise decimal points or exponents.

SEE ALSO   atof(), atoi(), strtod(), strtol(), strtoul().

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bsearch

void *bsearch (const void *key1, const void *buffer, size_t length, size_t width,
                  int (*compare) (const void *key2, const void *elem))

HEADER      stdlib.h

PURPOSE
To perform a binary search on the sorted array pointed to by buffer, until a match is found with the character pointed to by key1.
Where length is the number of array elements, and width the size in bytes of each element.
compare points to a user defined function, which carries out the actual comparison.
key2 points to the same character pointed to by key1 within bsearch(), while elem points to an individual element within the sorted array.

RESULT
If successful, bsearch() itself returns a generic pointer, containing the address of the first match with *key2, otherwise it returns the macro NULL (a NULL pointer).
The user defined function pointed to by compare is called at least once by bsearch().
Each time (*compare ()) tests the value within the array element pointed to by elem, to check whether it matches the value pointed to by key2.
It must return one of the following three values:-

Less than ZERO	If *key2 is less than *elem
ZERO	If *key2 is equal to *elem
More than ZERO	If *key2 is greater than *elem

NOTES
The array being searched must be sorted in ascending order, with the lowest array element containing the lowest value.
It must not contain duplicate records with identical keys.

SEE ALSO   qsort().

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calloc

void *calloc (size_t num, size_t length)

HEADER      stdlib.h

PURPOSE
To allocate an area of memory for an array of elements.
Where num is the number of individual elements and length their size in bytes.

RESULT
If successful, calloc() returns a generic pointer to the beginning of the area of memory allocated. Otherwise it returns the macro NULL (a NULL pointer).

NOTES
Unlike malloc(), calloc()initialises all the bits within the array to ZERO.

SEE ALSO   free(), realloc().

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ceil

double ceil (double upwards)

HEADER      math.h

PURPOSE
To calculate the double precision value passed to upwards, rounded up to its next whole number.

RESULT
If successful ceil() returns a double value, rounded up to the next whole number, otherwise if the value returned by ceil() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, ceil() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small ceil() returns 0.0.
When a domain error occurs, an implementation defined value is returned.

NOTES
If the value contained within upwards is not a double.
A domain error (an illegal argument) will occur, and the global integer errno set to EDOM.

SEE ALSO  fabs(), floor(), fmod().

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clearerr

void clearerr (FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To switch the file error flag off, and to reset the End Of File indicator associated with the file pointed to by file_pointer.

RESULT
No values are returned by this function.

SEE ALSO   feof(), ferror(), fgetpos(), ftell(), fseek(), fsetpos(), perror(), rewind().

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clock

clock_t clock (void)

HEADER       time.h

PURPOSE
To find out how long a distinct process within a program has been running.

RESULT
If successful, clock() returns the amount of time the entire program has been running, as an variable of type clock_t,
otherwise it returns (clock_t)-1.

NOTES
To convert the value returned by clock() into seconds divide it by the macro CLOCKS_PER_SEC.

SEE ALSO   asctime(), ctime(), difftime(), gmtime(), localtime(), mktime(), strftime(), time().

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cos

double cos (double angle)

HEADER      math.h

PURPOSE
To convert the double precision value passed to angle into its cosine.

RESULT
If successful, cos() returns the cosine of angle, in radians, otherwise if the value returned by cos() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, cos() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small cos() returns 0.0, but whether errno is set to ERANGE is implementation defined.

NOTES
If the value contained within angle is not a double number, a domain error (an illegal argument) will occur, the global integer errno set to EDOM, and an implementation defined value returned.

SEE ALSO   acos(), asin(), atan(),atan2(), cosh(), sin(), sinh(), tan(), tanh(), C99.

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cosh

double cosh (double angle)

HEADER      math.h

PURPOSE
To convert the double precision value passed to angle into its hyperbolic cosine.

RESULT
If successful, cosh() returns the hyperbolic cosine of angle, in radians, otherwise if the value returned by cosh() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, cosh() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small cosh() returns 0.0, but whether errno is set to ERANGE is implementation defined.

NOTES
If the value contained within angle is not a double number, a domain error (an illegal argument) will occur, the global integer errno set to EDOM, and an implementation defined value returned. .

SEE ALSO   acos(), asin(), atan(), atan2(), cos(), sin(), sinh(), tan(), tanh(), C99.

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ctime

char *ctime (const time_t *num_seconds)

HEADER      time.h

PURPOSE
To obtain the local time in the form of weekday, month, day of month, year, hours, minutes, seconds.
Which is placed in a string 26 characters long.

RESULT
If successful, ctime() returns a pointer to the buffer, where the character string has been stored, otherwise it returns an implementation defined value.

NOTES
Before calling ctime() num_seconds, a pointer to the calendar time, must be obtained by calling time().
The calendar time is stored as a object of type time_t, containing an implementation defined variable.
Each time either asctime(), or ctime() , is called, information stored within the string may be overwritten.

SEE ALSO   clock(), difftime().

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difftime

double difftime (time_t end, time_t begin)

HEADER      time.h

PURPOSE
To calculate the difference in seconds between the value passed to end (the end of a period of time), and that passed to begin (the beginning).

RESULT
If successful, difftime() returns a double precision value, containing the time difference in seconds.

NOTES
time_t is an object which stores time as an implementation defined variable.
The values contained within begin and end can be obtained by calling clock() on two separate occasions.

SEE ALSO   asctime(), clock(), ctime(), gmtime(), localtime(), mktime(), strftime(), time().

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div

div_t div (int number, int divider)

HEADER      stdlib.h

PURPOSE
To divide the value passed to number, by the value contained in divider.

RESULT
If successful, div() returns a div_t structure containing both the quotient, and the remainder of the division as two separate values, otherwise the value returned is implementation defined..

NOTES
If the value contained in divider is ZERO, the behavior is implementation defined.
However, many implementations terminate with an error message.
The div_t structure contains the following members, although they do not have to appear in that order:

typedef struct
                    { int quot;
                      int rem; }
      div_t div

SEE ALSO    abs(), labs(), ldiv()

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exit

void exit (int exit_code)

HEADER      stdlib.h

PURPOSE
To terminate the program which calls it.

RESULT
No values are returned by this function.

NOTES
exit() can be executed only once within a program.
If the value passed to exit_code is ZERO or EXIT_SUCCESS then the program has terminated normally, any other implementation defined value indicates an error of some kind.
The other macro used by exit_code is EXIT_FALSE .
When exit() is called any functions nominated by atexit() will be called in their reverse order.
Any files which are still open will be closed, after the buffers linked to them have been emptied.
All temporary files created by tmpfile() are deleted.

SEE ALSO   abort(),

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exp

double exp (double num)

HEADER      math.h

PURPOSE
To calculate the natural logarithm e, raised to the power of num.

RESULT
If successful, exp() returns a double precision value containing e to the power of num, otherwise if the value returned by exp() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, exp() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small exp() returns 0.0.
When a domain error occurs, an implementation defined value is returned.

NOTES
If the value contained within num is not a double, a domain error (an illegal argument) will occur, and the global integer errno set to EDOM.

SEE ALSO    log, C99 .

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fabs

double fabs (double num)

HEADER      math.h

PURPOSE
To calculate the absolute (e.g positive) value of num.

RESULT
If successful fabs() returns the absolute value of num as a double precision number, otherwise if the value returned by fabs() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, fabs() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small fabs() returns 0.0.
When a domain error occurs, an implementation defined value is returned.

NOTES
The absolute value of a number can only be positive.
If the value contained within num is not a double, a domain error (an illegal argument) will occur, and the global integer errno set to EDOM.

SEE ALSO   abs(), ceil(), floor(), fmod(), labs().

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fclose

int fclose (FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To close the file pointed to by file_pointer.

RESULT
If successful, fclose() will return ZERO. Otherwise it returns EOF.

NOTES
Information in the buffer pointed to by file_pointer will be emptied, and its contents flushed to that particular file.
However, data which is waiting to be read will be discarded.

SEE ALSO   fflush(), fopen(), freopen().

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feof

int feof (FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To check whether the end of the file pointed to by file_pointer has been reached.

RESULT
If the The End Of File indicator has been set, feof() will return NON ZERO .
Otherwise it returns ZERO.

NOTES
feof() is often used when working with binary files.
Calling clearerr(), fseek(), fsetpos(), or rewind() will clear the EOF indicator.

SEE ALSO  ferror(), perror().

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ferror

int ferror (FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To check for read/write errors in the file pointed to by file_pointer.

RESULT
If an error has been detected ferror() will return NON ZERO.

NOTES
Those error flags linked to file_pointer will remain set until either fclose(), rewind(), or clearerr() are called.
ferror() is often used when checking for errors in binary files.

SEE ALSO   feof(), perror().

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fflush

int fflush (FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To empty the contents of the output buffer, into the file pointed to by file_pointer.

RESULT
If successful, fflush() returns ZERO, otherwise it returns EOF.

NOTES
To flush ALL output buffers call fflush(NULL).
If the file has been opened for read/write, a read may not be followed by a write.
Or vice versa, without first calling either fflush(), fseek(), fsetpos(), or rewind().

SEE ALSO   fclose(), fopen(), freopen(), setbuf(), setvbuf().

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fgetc

int fgetc (FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To obtain the next character from the file pointed to by file_pointer, and increment the file position indicator.

RESULT
If successful, fgetc() will return the numerical value of the character read. Otherwise it will return EOF.

NOTES
fgetc() will also return EOF in the event of a read error.
When working with binary files, feof() must be called, to check that the End Of File position has been reached, and ferror() to check for errors.
If the file has been opened for read/write, a read may not be followed by a write.
Or vice versa, without first calling either fflush(), fseek(), fsetpos(), or rewind(), unless EOF was the last character read by fread()

SEE ALSO   fgets(), fputc(), fputs(), fwrite(), getc(), getchar(), gets(), putc(), putchar(), puts().

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fgetpos

int fgetpos (FILE *file_pointer, fpos_t *position)

HEADER      stdio.h

PURPOSE
To obtain the location of the file position indicator linked to *file_pointer, this value will then be stored in the area of memory pointed to by position.

RESULT
If successful, fgetpos() will return ZERO, otherwise it returns NON ZERO storing an implementation defined positive value in the global integer errno.

NOTES
The information stored in position can be used later by fsetpos() to return the file position indicator to its former location.

SEE ALSO   fflush(), fseek(), ftell(), rewind(), C99 .

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fgets

char *fgets (char *string, int width, FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To read a line of  width - 1 number of characters long into the buffer pointed to by string, from the file pointed to by file_pointer.

RESULT
If successful, fgets() will return the address of the input buffer, otherwise it returns the macro NULL (a NULL pointer).

NOTES
fgets() will continue to read characters until either the '\n' or EOF character is received.
If the length of the line of characters is less than width, the '\n' character will be copied into *string.
At the end of the string an '\0' character is added.
To check whether an error has occurred or the EOF character has been reached, either feof() or ferror() needs to be called.

SEE ALSO   fgetc(), fputc(), fread(), fwrite(), getc(), getchar(), gets(), putc(), putchar(), puts(), C99 .

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floor

double floor (double lower)

HEADER      math.h

PURPOSE
To round the double precision value passed to lower, down to its next whole number.

RESULT
If successful floor() returns a double value rounded down to its nearest whole number, otherwise if the value returned by floor() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, floor() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small floor() returns 0.0.
When a domain error occurs, an implementation defined value is returned.

NOTES
If the value contained within lower is not a double a domain error (an illegal argument) will occur, and the global integer errno set to EDOM.

SEE ALSO   ceil(), fabs(), fmod().

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fmod

double fmod (double first, double second)

HEADER      math.h

PURPOSE
To calculate the remainder of first divided by second.

RESULT
If successful fmod() returns a positive double precision value that is less than the value of second, otherwise if the value returned by fmod() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double, fmod() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small fmod() returns 0.0.
When a domain error occurs, an implementation defined value is returned.

NOTES
If the values of both first and second do not contain double precision numbers, a domain error (an illegal argument) will occur, and the global integer errno set to EDOM.
If the value of second is ZERO, whether a domain error occurs or fmod() returns 0.0 is implementation defined.

SEE ALSO   ceil(), fabs(), floor().

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fopen

FILE *fopen (const char *file_name, const char *mode)

HEADER      stdio.h

PURPOSE
To open the file, whose name is pointed to by file_name, where mode points to the type of access allowed.

RESULT
If successful, fopen() returns a pointer to the opened file.  Otherwise it returns the macro NULL
(a NULL pointer).

NOTES
Unless the length of *file_name is implementation defined, FILENAME_MAX will be the recommended size of the array.
The macro FOPEN_MAX determines the number of files that a program may have open at the same time, under MSDOS this will be at least eight.
Since three are always assigned to stdin (standard input), stdout (standard output), and stderr (standard error), that leaves five.
However, these three can if necessary be reassigned using freopen().
If the file has been opened for read/write, a read may not be followed by a write.
Or vice versa, without first calling either fflush(), fseek(), fsetpos(), or rewind().
Unless EOF was the last character read by fread().
The parameter pointed to by mode must contain one of the following values:

"a"	Open a text file for writing, create one if it does not already exist, append to the bottom of the file.
"a+"	Open a text file for reading and writing, create one if it does not already exist, append to the bottom of the file.
"ab"	Open a binary file for writing, create one if it does not already exist, append to the bottom of a file.
"ab+"	Open a binary file for reading and writing, create one if it does not already exist, append to the bottom of the file.
"r"	Open a text file, if it already exists for reading
"r+"	Open a text file, for reading and writing, if it already exists erase the contents.
"rb"	Open a binary file, if it already exists for reading.
"rb+"	Open a binary file, for reading and writing, if it already exists erase the contents.
"w"	Open a text file for writing, if it already exists erase the contents, otherwise create one.
"w+"	Open a text file for reading and writing, if it already exists erase the contents.
"wb"	Open a binary file for writing, if it already exists erase the contents.
"wb+"	Open a binary file for reading and writing, if it already exists erase the contents.

SEE ALSO  fclose(), ftell(), fgetpos(), C99 .

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fprintf

int fprintf (FILE *file_pointer, const char *format, [argument], ...)

HEADER      stdio.h

PURPOSE
To write a series of alphanumeric or printable characters to the file pointed to by file_pointer.
Where format points to the type of alphanumeric or printable character or characters, which will be contained in argument, and '...' indicates a variable number of arguments.

RESULT
If successful, fprintf returns the number of characters that have been written to the file, otherwise a negative value is returned.
A minimum of 509 characters can be written at any one time.

NOTES
The rules that apply to *format are the same as for printf().

SEE ALSO   fscanf(), scanf(), sprintf(), sscanf(), vfprintf(), vprintf(), vsprintf() C99

                                             MENU         LIBRARIES

fputc

int fputc (int ch, FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To write a character to the file pointed to by file_pointer, and increment its file position indicator.

RESULT
If successful, fputc() returns a positive value corresponding to the character written, otherwise it returns EOF.

NOTES
This function performs the same action as putc().
However, fputc() is more likely to be a function, not a macro.
Use ferror() to check whether an error has occurred.
The value passed to ch is converted by fputc() into an unsigned char.
If no file position indicator exists, the character is appended to the end of the file.

SEE ALSO   fgetc(), fgets(), fputs(), getc(), getchar(), gets(), putchar(), puts(), ungetc().

                                             MENU         LIBRARIES

fputs

int fputs (const char *string, FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To write the character array pointed to by string, into the file pointed to by file_pointer.

RESULT
If successful, fputs() returns a positive value. Otherwise it returns EOF.

NOTES
An '\n' character at the end of the string will not be written to the file.

SEE ALSO   fgetc(), fgets(), fputc(), getc(), getchar(), gets(), putc(), putchar(), puts(), ungetc(), C99 .

                                             MENU         LIBRARIES

fread

size_t fread (void *buffer, size_t width, size_t count, FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To read a group or groups of variables from a file pointed to by file_pointer, into the array pointed to by buffer.
Where count is the number of groups is to be read, and width their length in bytes.

RESULT
If successful, fread() returns the number of groups read, and increments the file position indicator, otherwise it returns ZERO.

NOTES
If the file pointed to by file_pointer is in text mode, all carriage return line feed characters will be replaced by single line feed characters.
If the file has been opened for read/write, a read may not be followed by a write, or vice versa, without first calling either fflush(), fseek(), fsetpos(),or rewind().
Unless EOF was the last character read by fread().

SEE ALSO   fwrite(), fgetpos(), ftell(), C99 .

                                             MENU         LIBRARIES

free

void free (void *memory_ptr)

HEADER      stdlib.h

PURPOSE
To free an area of memory.

RESULT
No values are returned by this function.

NOTES
Before calling free() the area of memory pointed to by memory_ptr, must have been assigned by calling either calloc(), malloc(), or realloc().
If the value contained in memory_ptr is the value NULL (a NULL pointer) no action occurs.

                                             MENU         LIBRARIES

freopen

FILE *freopen (const char *new_file, const char *mode, FILE *file_pointer)

HEADER      stdio.h

PURPOSE
To close the file, whose name is pointed to by file_pointer, which is then reassigned to another file.
Where new_file points to the name of the new file, and mode the file access mode.

RESULT
If successful, freopen() returns the address of the new file, otherwise it returns the macro NULL
(a NULL pointer).

NOTES
Unless the length of *new_file is implementation defined, FILENAME_MAX will be the recommended size of the array.
See fopen() for a complete description of *mode.
freopen() can be used to redirect stderr (standard error device), stdin (standard input device), and stdout (standard output device), to files on disk or to other devices.
freopen() clears the error and end of file indicators, linked to file_pointer.

SEE ALSO   fclose(), fflush(), setbuf(), setvbuf(), C99 .

                                             MENU         LIBRARIES

frexp

double frexp (double num, int *exp)

HEADER      math.h

PURPOSE
To convert the value passed to num into its mantissa,within the range of 0.5 to 0.999.

RESULT
If successful frexp() returns the mantissa of num, and stores the exponent in the integer pointed to by exp, otherwise if the value returned by frexp() is not a double, a range error (an illegal return value) will occur.
Or if the value is too large to fit inside a double,frexp() returns + or - HUGE_VAL, in either case errno is set to ERANGE.
If the value is too small, or num equals ZERO, frexp() returns 0.0.
When a domain error occurs, an implementation defined value is returned.

NOTES
If the values passed to frexp are not, a double precision number and an integer, in that order.
A domain error (an illegal argument) will result, and the global integer errno set to EDOM.
If num contains ZERO, frexp() will return ZERO, and store ZERO in *exp.

SEE ALSO   exp(), ldexp(), log(), log10(), modf().

                                             MENU         LIBRARIES

fscanf

int fscanf (FILE *file_pointer, const char *format, [argument],...)

HEADER      stdio.h

PURPOSE
To read information from the file pointed to by file_pointer, into the areas of memory specified by argument.
Where argument contains the addresses of those memory areas, *format describes the type of alphanumeric or printable characters contained in argument, and '... 'indicates a variable number of arguments.

RESULT
If is successful, fscanf() returns the number of groups of variables that have been read.
Otherwise it returns EOF in the case of an error, or ZERO if none were read.
To check whether the EOF character has been reached, call either feof() or ferror().

NOTES
See scanf() for a complete description of *format.

SEE ALSO