fgetc source

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



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.

NAME
       fgetc - get a byte from a stream

SYNOPSIS
       #include <stdio.h>

       int fgetc(FILE *stream);


DESCRIPTION
       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 st_atime field of the  file  associated
       with  stream for update. The st_atime field shall be marked for update by
       the first successful execution of fgetc(), fgets(),  fgetwc(),  fgetws(),
       fread(),  fscanf(),  getc(),  getchar(),  gets(), or scanf() using stream
       that returns data not supplied by a prior call to ungetc() or ungetwc().

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.

ERRORS
       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 process 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  process  is  ignoring  or  blocking  the
              SIGTTIN  signal  or  the process group 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.

EXAMPLES
       None.

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.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       feof(), ferror(), fopen(), getchar(), getc(), the Base Definitions volume
       of IEEE Std 1003.1-2001, <stdio.h>

COPYRIGHT
       Portions of this text are reprinted and  reproduced  in  electronic  form
       from  IEEE  Std 1003.1, 2003 Edition, Standard for Information Technology
       -- Portable Operating System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  6,  Copyright  (C)  2001-2003  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 .



IEEE/The Open Group                   2003                             FGETC(3P)

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