# fgetc

## 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



           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



           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 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._
    


## 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.
    


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