intro(3) [linux man page]

INTRO(3)						     Linux Programmer's Manual							  INTRO(3)

NAME

       intro - Introduction to library functions

DESCRIPTION

       Section	3  of  the  manual  describes all library functions excluding the library functions (system call wrappers) described in section 2,
       which implement system calls.

       Many of the functions described in the section are part of the Standard C Library (libc).  Some	functions  are	part  of  other  libraries
       (e.g.,  the  math  library,  libm, or the real-time library, librt) in which case the manual page will indicate the linker option needed to
       link against the required library (e.g., -lm and -lrt, respectively, for the aforementioned libraries).

       In some cases, the programmer must define a feature test macro in order to obtain the declaration of a function from the header file speci-
       fied  in the man page SYNOPSIS section.	(Where required, these feature test macros must be defined before including any header files.)	In
       such cases, the required macro is described in the man page.  For further information on feature test macros, see feature_test_macros(7).

CONFORMING TO

       Certain terms and abbreviations are used to indicate Unix variants and standards to which calls in this section conform.  See standards(7).

NOTES

   Authors and Copyright Conditions
       Look at the header of the manual page source for the author(s) and copyright conditions.  Note that these can be  different  from  page	to
       page!

SEE ALSO

       intro(2), errno(3), feature_test_macros(7), libc(7), standards(7)

COLOPHON

       This  page is part of release 3.27 of the Linux man-pages project.  A description of the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2010-09-10								  INTRO(3)

INTRO(3)						     Library Functions Manual							  INTRO(3)

NAME

       intro - introduction to library functions

SYNOPSIS

       #include <stdio.h>

       #include <math.h>

DESCRIPTION

       This section describes functions that may be found in various libraries, other than those functions that directly invoke UNIX system primi-
       tives, which are described in section 2.  Functions are divided into various libraries distinguished by the section number at  the  top	of
       the page:

       (3)   These  functions,	together  with those of section 2 and those marked (3S), constitute library libc, which is automatically loaded by
	     the C compiler cc(1) and the Fortran compiler f77(1).  The link editor ld(1) searches this library under the `-lc' option.   Declara-
	     tions for some of these functions may be obtained from include files indicated on the appropriate pages.

       (3M)  These functions constitute the math library, libm.  They are automatically loaded as needed by the Fortran compiler f77(1).  The link
	     editor searches this library under the `-lm' option.  Declarations for  these  functions  may  be	obtained  from	the  include  file
	     <math.h>.

       (3S)  These  functions  constitute  the	`standard  I/O package', see stdio(3).	These functions are in the library libc already mentioned.
	     Declarations for these functions may be obtained from the include file <stdio.h>.

       (3X)  Various specialized libraries have not been given distinctive captions.  The files in which these libraries are found  are  named	on
	     the appropriate pages.

FILES

       /lib/libc.a
       /lib/libm.a, /usr/lib/libm.a (one or the other)

SEE ALSO

       stdio(3), nm(1), ld(1), cc(1), f77(1), intro(2)

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.  The  values  of  EDOM
       and ERANGE are defined in the include file <math.h>.

ASSEMBLER

       In assembly language these functions may be accessed by simulating the C calling sequence.  For example, ecvt(3) might be called this way:

	      setd
	      mov  $sign,-(sp)
	      mov  $decpt,-(sp)
	      mov  ndigit,-(sp)
	      movf value,-(sp)
	      jsr  pc,_ecvt
	      add  $14.,sp

																	  INTRO(3)