intro.3

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.\" SCCSID: @(#)intro.3	3.1	11/24/87
.TH intro 3
.SH Name
intro \- introduction to library functions
.SH Description
.NXR "intro(3) keyword"
.NXA "subroutine" "\fIspecific subroutines\fP"
This section describes functions that may be found
in various libraries.  The library functions are those other than the
functions that directly invoke ULTRIX system primitives,
described in section 2.
.NXR "library" "functions"
Section 3 has the libraries physically grouped together.  
The functions described in this
section are grouped into various libraries:
.SH Sections 3 and 3s
The (3) functions are the standard C library functions.  The
C library also includes all the functions described in Section 2.  
.NXR "libc library" "contents"
.NXA "C library" "libc library"
These routines are
included for compatibility with other systems.  In particular,
a number of system call interfaces provided in 
4.2BSD have been included for source code compatibility.
The (3s) functions comprise the standard I/O library.  
Together with the
(3n), (3xti), (3yp) and (3) routines, these functions constitute
library \fIlibc\fP,
which is automatically loaded by the C compiler
(cc), the Pascal compiler (pc), and the FORTRAN compiler
(f77).
(FORTRAN
and Pascal are optional and may not be installed on your system.)
Declarations for these functions may be obtained from
the include file, <stdio.h>.
The link editor 
.MS ld 1
searches this library under the \-lc option.
Declarations for some of these functions may be obtained
from include files indicated on the appropriate pages.
.NT "VAX Only"
On VAX machines, the GFLOAT version of
.I libc
is used when you use the 
.MS cc 1
command with the
.B \-Mg
option, or you use the 
.MS ld 1
command with the
.B \-lcg
option.  
The GFLOAT version of
.IR libc
must be used with modules 
compiled with 
.MS cc 1
using the 
.B \-Mg
option. 
.sp
Note that neither the compiler nor the linker 
.MS ld 1
can detect when mixed double floating point types are used,
and your program may produce erroneous results if this occurs on a
VAX machine.
.NE
.SH Section 3cur
The (3cur) library routines make up the X/Open curses library.  These
routines are different from the 4.2BSD curses routines contained in
Section 3x.
.SH Section 3f
The (3f) functions are all functions callable from FORTRAN.  These
functions perform the same jobs as do the (3) functions.
An unsupported FORTRAN compiler, f77, is included in the VAX
distribution. FORTRAN is available as a layered product on both VAX
and RISC machines.
.SH Section 3int
The (3int) functions assist programs in supporting native language
interfaces.  They are found in the internationalization library
.IR libi .
.SH Section 3krb
The library of routines for the Kerberos authentication service. These
routines support the authentication of commonly networked applications
across machine boundaries in a distributed network.
.SH Section 3m
.NXR "libm library"  "contents"
The (3m) functions constitute the math library,
.IR libm .
They are automatically loaded as needed by the Pascal
compiler (pc)
and the FORTRAN compiler (f77).
The link editor searches this library under the 
.B \-lm 
option.  Declarations for these functions 
may be obtained from the include file, < math.h >.
.NT "VAX Only"
On VAX machines, the GFLOAT version of
.IR libm
is used when you use the 
.MS ld 1
command with the
.B \-lcg
option. Note that you must use
the GFLOAT version of
.IR libm
with modules compiled using the 
.MS cc 1
command with the
.B \-Mg
option. 
.sp
Note that neither the compiler nor the linker 
.MS ld 1
can detect when mixed double floating point
types are used, and the program may produce
erroneous results if this occurs on a VAX machine.
.NE
.SH Section 3ncs
This section describes the NCS (Network Computing System) library 
routines.
The Title, Name, and See Also sections of the NCS reference pages do not
contain the dollar ($) sign in the command names and library routines.
The actual NCS commands and library routines do contain the
dollar ($) sign.
.SH Section 3n
These functions constitute the internet network library,
.SH Section 3x
Various specialized libraries have not been given distinctive captions.
Files in which such libraries are found are named on appropriate pages.
.SH Section 3xti
The X/Open Transport Interface defines a 
transport service interface that is
independent of any specific transport provider.  
The interface is provided by
way of a set of library functions for the C programming language.
.SH Section 3yp
These functions are specific to the Yellow Pages (YP) service.
.SH Environmental Compatibility
.NXS "environment (System V)" "System V environment"
.NXR "System V environment" "specifying"
.NXS "environment (POSIX)" "POSIX environment"
.NXR "POSIX environment" "specifying"
The libraries in Sections 3, 3m, and 3s contain System V and POSIX
compatibility features that are available to general ULTRIX
programs.  This compatibility sometimes conflicts with
features already present in ULTRIX.  That is, the function
performed may be slightly different in the System V or POSIX environment.
These features are provided for applications that are being
ported from System V or written for a POSIX environment.
.PP
The descriptions in these sections include an ENVIRONMENT
section to describe any differences in function between
System V or POSIX and the standard C runtime library.
.PP
The System V compatibility features are not contained in the
standard C runtime library.  To get System V-specific behavior,
you must specify that the System V environment is to be used in
compiling and linking programs.  You can do this in one of two
ways:
.IP 1. 5
Using the \fB\-YSYSTEM_FIVE\fR option for the 
.PN cc
command.
.IP 2. 5
Globally setting the environment variable PROG_ENV to SYSTEM_FIVE.
If you are using the C shell, you would execute the following line,
or include it in your .login file:
.EX
setenv PROG_ENV SYSTEM_FIVE
.EE
If you are using the Bourne shell, you would execute the following
line, or include it in your .profile file:
.EX
PROG_ENV=SYSTEM_FIVE ; export PROG_ENV
.EE
.PP
In both cases, the 
.MS cc 1
command defines the preprocessor symbol SYSTEM_FIVE, so that the
C preprocessor, 
.PN /lib/cpp, 
will select the System V version of various data structures
and symbol definitions.
.PP
In addition, if 
.MS cc 1
invokes 
.MS ld 1 ,
the library libcV.a 
(the System V version of the Standard C library) is searched before
libc.a to resolve references to the
System-V-specific routines.  Also, if
\fB\-lm\fR is specified on either the 
.MS cc 1
or the
.MS ld 1
command line, then the
System V version of the math
library will be used instead of the regular ULTRIX math library.
.PP
The POSIX compatibility features are included in the library libcP.a, so
the only special action needed is to specify \fB-YPOSIX\fP on the
.MS cc 1
command line or set the environment variable PROG_ENV to POSIX.  Either
action will cause the
.MS cc 1
command to define the preprocessor symbol POSIX and 
search the POSIX library.
.SH Files
.TP 30
/usr/lib/libc.a 
.TP 
/usr/lib/lib_cg.a 
(VAX only)
.TP
/usr/lib/libm.a 	
.TP
/usr/lib/libc_p.a 
(VAX only)
.TP
/usr/lib/m_g.a     
(VAX only)
.TP
/usr/lib/libm_p.a  
(VAX only)
.fi
.SH Diagnostics
.NXR "libm library" "diagnostics and"
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
.I errno
is set to the value EDOM (domain error) or ERANGE (range error).
For further information, see 
.MS intro 2 .
The values of EDOM and ERANGE are defined in the include file
<math.h>.
.SH See Also
cc(1), ld(1), nm(1), intro(2)
intro(3m), intro(3n), intro(3ncs), intro(3s), intro(3xti)