NAME

intro − introduction to subroutines and libraries

SYNOPSIS

#include <stdio.h>

#include <math.h>

DESCRIPTION

This section describes functions found in various libraries, other than those functions that directly invoke UNIX system primitives, which are described in Section 2 of this volume.  Certain major collections are identified by a letter after the section number; all the libraries are pre-installed into process address space. 

(3C) These functions relate to communications.  Declarations for some of these functions may be obtained from #include files indicated on the appropriate pages. 

(3M) These functions constitute the math library, libm. Declarations for these functions may be obtained from the #include file <math.h>. 

(3S) These functions constitute the “standard I/O package” (see stdio(3S)). Declarations for these functions may be obtained from the #include file <stdio.h>. 

(3X) Various specialized libraries.  The files in which these libraries are found are given on the appropriate pages. 

The descriptions of some functions refer to NULL.  This is the value that is obtained by casting 0 into a character pointer.  The C language guarantees that this value will not match that of any legitimate pointer, so many functions that return pointers return it, for example, to indicate an error.  NULL is defined in <stdio.h> as 0; the user can include his own definition if he is not using <stdio.h>. 

FILES

/lib/libc.a
/lib/libm.a

SEE ALSO

ar(1), cc(1), ld(1), intro(2), stdio(3S). 

DIAGNOSTICS

Functions in the math library (3M) may return conventional values when the function is undefined for the given arguments or when the value is not representable.  In these cases, the external variable errno (see intro(2)) is set to the value EDOM or ERANGE.