intro(3s)intro(3s)Name
stdio - standard buffered input/output package
Syntax
#include <stdio.h>
FILE *stdin;
FILE *stdout;
FILE *stderr;
Description
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
Diagnostics
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
input.
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.
Files
/lib/libc.a
/usr/lib/libcg.a (VAX only)
See Alsoopen(2), close(2), read(2), write(2), fread(3s), fseek(3s), ferror(3s), fclose(3s), fopen(3s)intro(3s)
Check Out this Related Man Page
STDIN(P) POSIX Programmer's Manual STDIN(P)
NAME
stderr, stdin, stdout - standard I/O streams
SYNOPSIS
#include <stdio.h>
extern FILE *stderr, *stdin, *stdout;
DESCRIPTION
A file with associated buffering is called a stream and is declared to be a pointer to a defined type FILE. The fopen() function shall cre-
ate certain descriptive data for a stream and return a pointer to designate the stream in all further transactions. Normally, there are
three open streams with constant pointers declared in the <stdio.h> header and associated with the standard open files.
At program start-up, three streams shall be predefined and need not be opened explicitly: standard input (for reading conventional input),
standard output (for writing conventional output), and standard error (for writing diagnostic output). When opened, the standard error
stream is not fully buffered; the standard input and standard output streams are fully buffered if and only if the stream can be determined
not to refer to an interactive device.
The following symbolic values in <unistd.h> define the file descriptors that shall be associated with the C-language stdin, stdout, and
stderr when the application is started:
STDIN_FILENO
Standard input value, stdin. Its value is 0.
STDOUT_FILENO
Standard output value, stdout. Its value is 1.
STDERR_FILENO
Standard error value, stderr. Its value is 2.
The stderr stream is expected to be open for reading and writing.
RETURN VALUE
None.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
None.
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
fclose() , feof() , ferror() , fileno() , fopen() , fread() , fseek() , getc() , gets() , popen() , printf() , putc() , puts() , read() ,
scanf() , setbuf() , setvbuf() , tmpfile() , ungetc() , vprintf() , the Base Definitions volume of IEEE Std 1003.1-2001, <stdio.h>,
<unistd.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE
and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
online at http://www.opengroup.org/unix/online.html .
IEEE /The Open Group 2003 STDIN(P)