(libc.info.gz) EOF and Errors

Info Catalog

(libc.info.gz) Formatted Input

(libc.info.gz) I/O on Streams

(libc.info.gz) Error Recovery

 
 12.15 End-Of-File and Errors
 ============================
 
 Many of the functions described in this chapter return the value of the
 macro `EOF' to indicate unsuccessful completion of the operation.
 Since `EOF' is used to report both end of file and random errors, it's
 often better to use the `feof' function to check explicitly for end of
 file and `ferror' to check for errors.  These functions check
 indicators that are part of the internal state of the stream object,
 indicators set if the appropriate condition was detected by a previous
 I/O operation on that stream.
 
  -- Macro: int EOF
      This macro is an integer value that is returned by a number of
      narrow stream functions to indicate an end-of-file condition, or
      some other error situation.  With the GNU library, `EOF' is `-1'.
      In other libraries, its value may be some other negative number.
 
      This symbol is declared in `stdio.h'.
 
  -- Macro: int WEOF
      This macro is an integer value that is returned by a number of wide
      stream functions to indicate an end-of-file condition, or some
      other error situation.  With the GNU library, `WEOF' is `-1'.  In
      other libraries, its value may be some other negative number.
 
      This symbol is declared in `wchar.h'.
 
  -- Function: int feof (FILE *STREAM)
      The `feof' function returns nonzero if and only if the end-of-file
      indicator for the stream STREAM is set.
 
      This symbol is declared in `stdio.h'.
 
  -- Function: int feof_unlocked (FILE *STREAM)
      The `feof_unlocked' function is equivalent to the `feof' function
      except that it does not implicitly lock the stream.
 
      This function is a GNU extension.
 
      This symbol is declared in `stdio.h'.
 
  -- Function: int ferror (FILE *STREAM)
      The `ferror' function returns nonzero if and only if the error
      indicator for the stream STREAM is set, indicating that an error
      has occurred on a previous operation on the stream.
 
      This symbol is declared in `stdio.h'.
 
  -- Function: int ferror_unlocked (FILE *STREAM)
      The `ferror_unlocked' function is equivalent to the `ferror'
      function except that it does not implicitly lock the stream.
 
      This function is a GNU extension.
 
      This symbol is declared in `stdio.h'.
 
    In addition to setting the error indicator associated with the
 stream, the functions that operate on streams also set `errno' in the
 same way as the corresponding low-level functions that operate on file
 descriptors.  For example, all of the functions that perform output to a
 stream--such as `fputc', `printf', and `fflush'--are implemented in
 terms of `write', and all of the `errno' error conditions defined for
 `write' are meaningful for these functions.  For more information about
 the descriptor-level I/O functions, see  Low-Level I/O.
 

Info Catalog

(libc.info.gz) Formatted Input

(libc.info.gz) I/O on Streams

(libc.info.gz) Error Recovery