получить байт из потока (get a byte from a stream)
Пролог (Prolog)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
Имя (Name)
fgetc — get a byte from a stream
Синопсис (Synopsis)
#include <stdio.h>
int fgetc(FILE *stream);
Описание (Description)
The functionality described on this reference page is aligned
with the ISO C standard. Any conflict between the requirements
described here and the ISO C standard is unintentional. This
volume of POSIX.1‐2017 defers to the ISO C standard.
If the end-of-file indicator for the input stream pointed to by
stream is not set and a next byte is present, the fgetc()
function shall obtain the next byte as an unsigned char converted
to an int, from the input stream pointed to by stream, and
advance the associated file position indicator for the stream (if
defined). Since fgetc() operates on bytes, reading a character
consisting of multiple bytes (or ``a multi-byte character'') may
require multiple calls to fgetc().
The fgetc() function may mark the last data access timestamp of
the file associated with stream for update. The last data access
timestamp shall be marked for update by the first successful
execution of fgetc(), fgets(), fread(), fscanf(), getc(),
getchar(), getdelim(), getline(), gets(), or scanf() using stream
that returns data not supplied by a prior call to ungetc().
Возвращаемое значение (Return value)
Upon successful completion, fgetc() shall return the next byte
from the input stream pointed to by stream. If the end-of-file
indicator for the stream is set, or if the stream is at end-of-
file, the end-of-file indicator for the stream shall be set and
fgetc() shall return EOF. If a read error occurs, the error
indicator for the stream shall be set, fgetc() shall return EOF,
and shall set errno to indicate the error.
Ошибки (Error)
The fgetc() function shall fail if data needs to be read and:
EAGAIN The O_NONBLOCK flag is set for the file descriptor
underlying stream and the thread would be delayed in the
fgetc() operation.
EBADF The file descriptor underlying stream is not a valid file
descriptor open for reading.
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 process is in a
background process group attempting to read from its
controlling terminal, and either the calling thread is
blocking SIGTTIN or the process is ignoring SIGTTIN or the
process group of the process is orphaned. This error may
also be generated for implementation-defined 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() function may fail if:
ENOMEM Insufficient storage space is available.
ENXIO A request was made of a nonexistent device, or the request
was outside the capabilities of the device.
The following sections are informative.
Примеры (Examples)
None.
Использование в приложениях (Application usage)
If the integer value returned by fgetc() 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-defined.
The ferror() or feof() functions must be used to distinguish
between an error condition and an end-of-file condition.
Обоснование (Rationale)
None.
Будущие направления (Future directions)
None.
Смотри также (See also)
Section 2.5, Standard I/O Streams, feof(3p), ferror(3p),
fgets(3p), fread(3p), fscanf(3p), getchar(3p), getc(3p),
gets(3p), ungetc(3p)
The Base Definitions volume of POSIX.1‐2017, stdio.h(0p)
