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.1‐2017 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().

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() 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.

              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.

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

       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.1‐2017, stdio.h(0p)

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  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.opengroup.org/unix/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               2017                         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)