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 certain
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 associ‐
ated 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:
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
Note that neither the compiler nor the linker can detect when mixed
double floating point types are used, and the program may produce erro‐
neous results if this occurs.
System V Compatibility
This library contains System V compatibility features that are avail‐
able 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 out‐
put (input) stream, or a FILE pointer designates corrupt or otherwise
unintelligible FILE data.
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.
See Alsoopen(2), close(2), read(2), write(2), fread(3s), fseek(3s), ferror(3s),