GETC(3S)GETC(3S)NAME
getc, getchar, fgetc, getw, getc_unlocked, getchar_unlocked - get
character or word from a stream
SYNOPSIS
#include <stdio.h>
int getc (FILE *stream);
int getchar (void);
int fgetc (FILE *stream);
int getw (FILE *stream);
int getc_unlocked (FILE *stream);
int getchar_unlocked (void);
DESCRIPTION
Fgetc and getc return the next character (if it exists) from the named
input stream, as an unsigned character converted to an integer. It also
moves the file pointer, if defined, ahead one character in stream.
getchar is defined as getc(stdin). Each of getc,getchar and fgetc exist
as functions in the C library. Getc and getchar are also available as
macros in <stdio.h> (see below under CAVEATS for important details on the
implementation of these macros.)
Getw returns the next word (i.e., integer) from the named input stream.
Getw increments the associated file pointer, if defined, to point to the
next integer-sized word. Getw assumes no special alignment in the file.
The getc_unlocked and getchar_unlocked functions are equivalent to the
getc and getchar functions, respectively. However, these functions are
not thread-safe and thus must only be called under the protection of the
flockfile (or ftrylockfile) and funlockfile functions.
SEE ALSOfclose(3S), ferror(3S), fopen(3S), fread(3S), gets(3S), putc(3S),
scanf(3S), stdio(3S), ungetc(3S).
DIAGNOSTICS
These functions return the constant EOF at end-of-file or upon an error.
Because EOF is a valid integer, it is not sufficient to detect getw
errors. ferror(3S) must be used as well.
WARNING
If the integer value returned by getc, getchar, or fgetc is stored into a
character variable and then compared against the integer constant EOF,
the comparison may never succeed, because sign-extension of a character
on widening to integer is machine-dependent.
Page 1
GETC(3S)GETC(3S)CAVEATS
When using the macro versions of getc and getchar, the stream argument
may be evaluated more than once. Thus, it must not be an expression with
side-effects. In particular, getc(*f++) does not work sensibly. In
these situations, the macro must either be #undef'd, or fgetc should be
used instead.
Because of possible differences in word length and byte ordering, files
written using putw are machine-dependent, and may not be read using getw
on a different processor.
BUGS
When using the macros for getc and getchar, hidden external names may be
referenced. Although these names are prefixed with an underscore, they
may conflict with names which the ANSI C Standard reserves for the user
when appearing in a local context. It is thus recommended that users of
these macros reserve all names which begin with an underscore for the
implementation, and avoid defining such names, even in a local context.
Page 2
