fgetc(3p) — Linux manual page


FGETC(3P)                 POSIX Programmer's Manual                FGETC(3P)

PROLOG         top

       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.

NAME         top

       fgetc — get a byte from a stream

SYNOPSIS         top

       #include <stdio.h>

       int fgetc(FILE *stream);

DESCRIPTION         top

       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.1‐2008 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

       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().

RETURN VALUE         top

       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.

ERRORS         top

       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()

       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.

              The file is a regular file and an attempt was made to read at
              or beyond the offset maximum associated with the corresponding

       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.

EXAMPLES         top



       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.

RATIONALE         top




SEE ALSO         top

       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.1‐2008, stdio.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2013 Edition, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The Open
       Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1
       applied.) 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.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the
       source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                           FGETC(3P)

Pages that refer to this page: stdio.h(0p)fgets(3p)fread(3p)fscanf(3p)getc(3p)getchar(3p)getdelim(3p)gets(3p)