Standard C Library Functions fgetc(3C)
NAME
fgetc, getc, getcunlocked, getchar, getcharunlocked, getw
- get a byte from a stream
SYNOPSIS
#include
int fgetc(FILE *stream);
int getc(FILE *stream);
int getcunlocked(FILE *stream);
int getchar(void);
int getcharunlocked(void);
int getw(FILE *stream);
DESCRIPTION
The fgetc() function obtains the next byte (if present) as
an unsigned char converted to an int, from the input stream
pointed to by stream, and advances the associated file posi-
tion indicator for the stream (if defined).
For standard-conforming (see standards(5)) applications, if
the end-of-file indicator for the stream is set, fgetc()
returns EOF whether or not a next byte is present.
The fgetc() function may mark the statime field of the file
associated with stream for update. The statime field will
be marked for update by the first successful execution of
fgetc(), fgets(3C), fread(3C), fscanf(3C), getc(),
getchar(), gets(3C) or scanf(3C) using stream that returns
data not supplied by a prior call to ungetc(3C) or
ungetwc(3C).
The getc() function is functionally identical to fgetc(),
except that it is implemented as a macro. It runs faster
than fgetc(), but it takes up more space per invocation and
its name cannot be passed as an argument to a function call.
SunOS 5.11 Last change: 15 Oct 2003 1
Standard C Library Functions fgetc(3C)
The getchar() routine is equivalent to getc(stdin). It is
implemented as a macro.
The getcunlocked() and getcharunlocked() routines are
variants of getc() and getchar(), respectively, that do not
lock the stream. It is the caller's responsibility to
acquire the stream lock before calling these routines and
releasing the lock afterwards; see flockfile(3C) and
stdio(3C). These routines are implemented as macros.
The getw() function reads the next word from the stream. The
size of a word is the size of an int and may vary from
environment to environment. The getw() function presumes no
special alignment in the file.
The getw() function may mark the statime field of the file
associated with stream for update. The statime field will
be marked for update by the first successful execution of
fgetc(), fgets(3C), fread(3C), getc(), getchar(), gets(3C),
fscanf(3C) or scanf(3C) using stream that returns data not
supplied by a prior call to ungetc(3C).
RETURN VALUES
Upon successful completion, fgetc(), getc(),
getcunlocked(), getchar(), getcharunlocked(), and getw()
return the next byte from the input stream pointed to by
stream. If the stream is at end-of-file, the end-of-file
indicator for the stream is set and these functions return
EOF. For standard-conforming (see standards(5)) applica-
tions, if the end-of-file indicator for the stream is set,
these functions return EOF whether or not the stream is at
end-of-file. If a read error occurs, the error indicator for
the stream is set, EOF is returned, and errno is set to
indicate the error.
ERORS
The fgetc(), getc(), getcunlocked(), getchar(),
getcharunlocked(), and getw() functions will fail if data
needs to be read and:
EAGAIN The ONONBLOCK flag is set for the file
descriptor underlying stream and the process
would be delayed in the fgetc() operation.
EBADF The file descriptor underlying stream is not a
valid file descriptor open for reading.
SunOS 5.11 Last change: 15 Oct 2003 2
Standard C Library Functions fgetc(3C)
EINTR The read operation was terminated due to the
receipt of a signal, and no data was
transferred.
EIO A physical I/O error has occurred, or the pro-
cess is in a background process group attempt-
ing to read from its controlling terminal, and
either the process is ignoring or blocking the
SIGTIN signal or the process group is
orphaned. This error may also be generated for
implementation-dependent reasons.
EOVERFLOW The file is a regular file and an attempt was
made to read at or beyond the offset maximum
associated with the corresponding stream.
The fgetc(), getc(), getcunlocked(), getchar(),
getcharunlocked(), and getw() functions may fail if:
ENOMEM Insufficient storage space is available.
ENXIO A request was made of a non-existent device, or
the request was outside the capabilities of the
device.
USAGE
If the integer value returned by fgetc(), getc(),
getcunlocked(), getchar(), getcharunlocked(), and getw()
is stored into a variable of type char and then compared
against the integer constant EOF, the comparison may never
succeed, because sign-extension of a variable of type char
on widening to integer is implementation-dependent.
The ferror(3C) or feof(3C) functions must be used to distin-
guish between an error condition and an end-of-file condi-
tion.
Functions exist for the getc(), getcunlocked(), getchar(),
and getcharunlocked() macros. To get the function form, the
macro name must be undefined (for example, #undef getc).
When the macro forms are used, getc() and getcunlocked()
evaluate the stream argument more than once. In particular,
SunOS 5.11 Last change: 15 Oct 2003 3
Standard C Library Functions fgetc(3C)
getc(*f]); does not work sensibly. The fgetc() function
should be used instead when evaluating the stream argument
has side effects.
Because of possible differences in word length and byte ord-
ering, files written using getw() are machine-dependent, and
may not be read using getw() on a different processor.
The getw() function is inherently byte stream-oriented and
is not tenable in the context of either multibyte character
streams or wide-character streams. Application programmers
are recommended to use one of the character-based input
functions instead.
ATRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
ATRIBUTE TYPE ATRIBUTE VALUE
Interface Stability fgetc(), getc(),
getcunlocked(), getchar(),
and getcharunlocked() are
Standard.
MT-Level See NOTES below.
SEE ALSO
Intro(3), fsetlocking(3C), fclose(3C), feof(3C),
fgets(3C), fgetwc(3C), fgetws(3C), flockfile(3C), fopen(3C),
fread(3C), fscanf(3C), gets(3C), putc(3C), scanf(3C),
stdio(3C), ungetc(3C), ungetwc(3C), attributes(5), stan-
dards(5)
NOTES
The fgetc(), getc(), getchar(), and getw() routines are MT-
Safe in multithreaded applications. The getcunlocked() and
getcharunlocked() routines are unsafe in multithreaded
applications.
SunOS 5.11 Last change: 15 Oct 2003 4
|
