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DESCRIPTION
This chapter describes all the library functions, excluding the library functions described in Part 2, which implement system calls. The various function groups are identified by a letter that is appended to the chapter number:
| (3C) | These functions—the functions from Chapter 2 and from Chapter 3S—are contained in the C standard library libc, which will be used by cc(1) by default. |
| (3S) | These functions are parts of the stdio(3S) library. They are contained in the standard C library libc. |
| (3M) | These functions are contained in the arithmetic library libm. They are used by the f77(1) FORTRAN compiler by default, but not by the cc(1) C compiler, which needs the option _lm. |
| (3F) | These functions are part of the FORTRAN library libF77. There are no special compiler flags needed to use these functions. |
| (3X) | Various special libraries. The manual pages documenting their functions specify the library names. |
AUTHORS
Look at the header of the manual page for the author(s) and copyright conditions. Note that these can be different from page to page!
Linux, 13 December 1995
abort—Causes abnormal program termination
SYNOPSIS
#include <stdlib.h> void abort(void);
DESCRIPTION
The abort() function causes abnormal program termination unless the signal SIGABORT is caught and the signal handler does not return. If the abort() function causes program termination, all open streams are closed and flushed.
If the SIGABORT function is blocked or ignored, the abort() function will still override it.
RETURN VALUE
The abort() function never returns.
CONFORMS TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
sigaction(2), exit(3)
GNU, 12 April 1993
abs—Computes the absolute value of an integer
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SYNOPSIS
#include <stdlib.h> int abs(int j);
DESCRIPTION
The abs() function computes the absolute value of the integer argument j.
RETURN VALUE
Returns the absolute value of the integer argument.
CONFORMS TO
SVID 3, POSIX, BSD 4.3, ISO 9899
NOTES
Trying to take the absolute value of the most negative integer is not defined.
SEE ALSO
ceil(3), floor(3), fabs(3), labs(3), rint(3)
GNU, 6 June 1993
acos—Arc cosine function
SYNOPSIS
#include <math.h> double acos(double x);
DESCRIPTION
The acos() function calculates the arc cosine of x; that is the value whose cosine is x. If x falls outside the range _1 to 1, acos() fails and errno is set.
RETURN VALUE
The acos() function returns the arc cosine in radians; the value is mathematically defined to be between 0 and pi (inclusive).
ERRORS
EDOM x is out of range.
CONFORMS TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
asin(3), atan(3), atan2(3), cos(3), sin(3), tan(3)
8 June 1993
acosh—Inverse hyperbolic cosine function
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SYNOPSIS
#include <math.h> double acosh(double x);
DESCRIPTION
The acosh() function calculates the inverse hyperbolic cosine of x; that is the value whose hyperbolic cosine is x. If x is less than 1.0, acosh() returns not-a-number (NaN), and errno is set.
ERRORS
| EDOM | x is out of range. |
CONFORMS TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
asinh(3), atanh(3), cosh(3), sinh(3), tanh(3)
13 June 1993
alloca—Memory allocator
SYNOPSIS
#include <stdlib.h> void *alloca( size_t size);
DESCRIPTION
The alloca function allocates size bytes of space in the stack frame of the caller. This temporary space is automatically freed on return.
RETURN VALUES
The alloca function returns a pointer to the beginning of the allocated space. If the allocation fails, a NULL pointer is returned.
CONFORMS TO
There is evidence that the alloca function appeared in 32v, pwb, pwb.2, 3bsd, and 4bsd. There is a man page for it in BSD 4.3. Linux uses the GNU version.
BUGS
The alloca function is machine dependent.
SEE ALSO
brk(2), pagesize(2), calloc(3), malloc(3), realloc(3)
GNU, 29 November 1993
asin—Arc sine function
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SYNOPSIS
#include <math.h> double asin(double x);
DESCRIPTION
The asin() function calculates the arc sine of x, which is the value whose sine is x. If x falls outside the range _1 to 1, asin() fails and errno is set.
RETURN VALUE
The asin() function returns the arc sine in radians, and the value is mathematically defined to be between -PI/2 and PI/2 (inclusive).
ERRORS
| EDOM | x is out of range. |
CONFORMS TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
acos(3), atan(3), atan2(3), cos(3), sin(3), tan(3)
8 June 1993
asinh—Inverse hyperbolic sine function
SYNOPSIS
#include <math.h> double asinh(double x);
DESCRIPTION
The asinh() function calculates the inverse hyperbolic sine of x—that is, the value whose hyperbolic sine is x.
CONFORMS TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
acosh(3), atanh(3), cosh(3), sinh(3), tanh(3)
13 June 1993
assert—Abort the program if assertion is false
SYNOPSIS
#include <assert.h> void assert (int expression);
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DESCRIPTION
assert() prints an error message to standard output and terminates the program by calling abort() if expression is false (that is, evaluates to 0). This only happens when the macro NDEBUG is undefined.
RETURN VALUE
No value is returned.
CONFORMS TO
ISO9899 (ANSI C)
BUGS
assert() is implemented as a macro; if the expression tested has side effects, program behavior will be different depending on whether NDEBUG is defined. This may create Heisenbugs, which go away when debugging is turned on.
SEE ALSO
exit(3), abort(3)
GNU, 4 April 1993
atan—Arc tangent function
SYNOPSIS
#include <math.h> double atan(double x);
DESCRIPTION
The atan() function calculates the arc tangent of x—that is, the value whose tangent is x.
RETURN VALUE
The atan() function returns the arc tangent in radians, and the value is mathematically defined to be between -PI/2 and PI/2 (inclusive).
CONFORMS TO
SVID 3, POSIX, BSD 4.3, ISO 9899
SEE ALSO
acos(3), asin(3), atan2(3), cos(3), sin(3), tan(3)
8 June 1993
atan2—Arc tangent function of two variables
SYNOPSIS
#include <math.h> double atan2(double y, double x);