03-14-2010
Quote:
Originally Posted by
jlliagre
While I would mostly agree with the file descriptor definition, a file pointer is not usually what you describe but commonly used to refer to what the standard C library uses to handle files (FILE *).
The associated functions are fopen, fclose, fread, fwrite, fscanf and the likes.
I would also note that a file pointer has an associated file descriptor used by the library functions to do the actual I/O calls to the kernel. You can get the associated fd using the fileno function.
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STDIO(3S) STDIO(3S)
NAME
stdio - standard buffered input/output package
SYNOPSIS
#include <stdio.h>
FILE *stdin;
FILE *stdout;
FILE *stderr;
DESCRIPTION
The functions described in Sections 3S constitute an efficient user-level buffering scheme. The in-line macros getc and putc(3) handle
characters quickly. The higher level routines gets, fgets, scanf, fscanf, fread, puts, fputs, printf, fprintf, fwrite all use getc and
putc; 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. Fopen(3) 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 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: getc, getchar, putc, putchar, feof, ferror,
fileno.
SEE ALSO
open(2), close(2), read(2), write(2)
DIAGNOSTICS
The value EOF is returned uniformly to indicate that a FILE pointer has not been initialized with fopen, input (output) has been attempted
on an output (input) stream, or a FILE pointer designates corrupt or otherwise unintelligible FILE data.
STDIO(3S)