stdio - standard buffered input/output package
The functions described in section 3s constitute a user-level buffering scheme. The in-line macros and handle characters quickly. The
higher level routines all use and they can be freely intermixed.
A file with associated buffering is called a stream, and is declared to be a pointer to a defined type FILE. The subroutine creates cer-
tain descriptive data for a stream and returns a pointer to designate the stream in all further transactions. There are three normally
open streams with constant pointers declared in the include file and associated with the standard open files:
stdin standard input file
stdout standard output file
stderr standard error file
A constant `pointer' NULL(0) designates no stream at all.
An integer constant EOF (-1) is returned upon end of file or error by integer functions that deal with streams.
Any routine that uses the standard input/output package must include the header file <stdio.h> of pertinent macro definitions. The func-
tions and constants mentioned in sections labeled 3S are declared in the include file and need no further declaration. The constants, and
the following `functions' are implemented as macros; redeclaration of these names is perilous: On VAX machines, the GFLOAT version of libc
is used when you use the command with the -Mg option, or you use the command with the -lcg option. The GFLOAT version of libc must be used
with modules compiled with using the -Mg option.
Also note that neither the compiler nor the linker can detect when mixed double floating point types are used, and the program may produce
erroneous results if this occurs on VAX machines.
System V Compatibility
This library contains System V compatibility features that are available to general ULTRIX programs. For a discussion of how these fea-
tures are documented, and how to specify that the System V environment is to be used in compiling and linking your programs, see
The value EOF is returned uniformly to indicate that a FILE pointer has not been initialized with input (output) has been attempted on an
output (input) stream, or a FILE pointer designates corrupt or otherwise unintelligible FILE data.
For purposes of efficiency, this implementation of the standard library has been changed to line buffer output to a terminal by default and
attempts to do this transparently by flushing the output whenever a from the standard input is necessary. This is almost always transpar-
ent, but may cause confusion or malfunctioning of programs which use standard I/O routines but use themselves to read from the standard
In cases where a large amount of computation is done after printing part of a line on an output terminal, it is necessary to the standard
output before going off and computing so that the output will appear.
/usr/lib/libcg.a (VAX only)
open(2), close(2), read(2), write(2), fread(3s), fseek(3s), ferror(3s), fclose(3s), fopen(3s)