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    The following form allows you to view linux man pages.

    Command:

    fdopen

    
    
    

    SYNOPSIS

           #include <stdio.h>
    
           FILE *fopen(const char *path, const char *mode);
    
           FILE *fdopen(int fd, const char *mode);
    
           FILE *freopen(const char *path, const char *mode, FILE *stream);
    
       Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
    
           fdopen(): _POSIX_C_SOURCE >= 1 || _XOPEN_SOURCE || _POSIX_SOURCE
    
    
    

    DESCRIPTION

           The fopen() function opens the file whose name is the string pointed to
           by path and associates a stream with it.
    
           The argument mode points to a string beginning with one of the  follow-
           ing sequences (possibly followed by additional characters, as described
           below):
    
           r      Open text file for reading.  The stream  is  positioned  at  the
                  beginning of the file.
    
           r+     Open  for  reading and writing.  The stream is positioned at the
                  beginning of the file.
    
           w      Truncate file to zero length or create text  file  for  writing.
                  The stream is positioned at the beginning of the file.
    
           w+     Open  for  reading  and writing.  The file is created if it does
                  not exist, otherwise it is truncated.  The stream is  positioned
                  at the beginning of the file.
    
           a      Open  for  appending (writing at end of file).  The file is cre-
                  ated if it does not exist.  The stream is positioned at the  end
                  of the file.
    
           a+     Open  for  reading  and appending (writing at end of file).  The
                  file is created if it does not exist.  The initial file position
                  for  reading  is  at  the  beginning  of the file, but output is
                  always appended to the end of the file.
    
           The mode string can also include the letter 'b' either as a last  char-
           acter  or as a character between the characters in any of the two-char-
           acter strings described above.  This is strictly for compatibility with
           C89  and has no effect; the 'b' is ignored on all POSIX conforming sys-
           tems, including Linux.  (Other systems may treat text files and  binary
           files  differently, and adding the 'b' may be a good idea if you do I/O
           to a binary file and expect that your program may be ported to non-UNIX
           environments.)
    
           fseek(..., 0L, SEEK_CUR) called for its synchronizing side effect.
    
           Opening a file in append mode (a as the first character of mode) causes
           all subsequent write operations to this stream to occur at end-of-file,
           as if preceded the call:
    
               fseek(stream, 0, SEEK_END);
    
           The  fdopen()  function  associates  a  stream  with  the existing file
           descriptor, fd.  The mode of the stream (one of the values  "r",  "r+",
           "w",  "w+",  "a",  "a+")  must  be compatible with the mode of the file
           descriptor.  The file position indicator of the new stream  is  set  to
           that  belonging  to  fd,  and  the error and end-of-file indicators are
           cleared.  Modes "w" or "w+" do not cause truncation of the  file.   The
           file  descriptor is not dup'ed, and will be closed when the stream cre-
           ated by fdopen() is closed.  The  result  of  applying  fdopen()  to  a
           shared memory object is undefined.
    
           The  freopen() function opens the file whose name is the string pointed
           to by path and associates the stream pointed to by stream with it.  The
           original  stream  (if  it exists) is closed.  The mode argument is used
           just as in the fopen() function.  The  primary  use  of  the  freopen()
           function  is  to change the file associated with a standard text stream
           (stderr, stdin, or stdout).
    
    
    

    RETURN VALUE

           Upon successful completion fopen(), fdopen()  and  freopen()  return  a
           FILE pointer.  Otherwise, NULL is returned and errno is set to indicate
           the error.
    
    
    

    ERRORS

           EINVAL The  mode  provided  to  fopen(),  fdopen(),  or  freopen()  was
                  invalid.
    
           The  fopen(),  fdopen()  and  freopen() functions may also fail and set
           errno for any of the errors specified for the routine malloc(3).
    
           The fopen() function may also fail and set errno for any of the  errors
           specified for the routine open(2).
    
           The fdopen() function may also fail and set errno for any of the errors
           specified for the routine fcntl(2).
    
           The freopen() function may also fail and  set  errno  for  any  of  the
           errors specified for the routines open(2), fclose(3) and fflush(3).
    
    
    

    CONFORMING TO

           The fopen() and freopen() functions conform to C89.  The fdopen() func-
           tion conforms to POSIX.1-1990.
    
    
    

    NOTES

       Glibc notes
                  calls   (read(2),  write(2)).   Currently,  use  of  mmap(2)  is
                  attempted only for a file opened for reading.
    
           x      Open the file exclusively (like the O_EXCL flag of open(2)).  If
                  the  file  already exists, fopen() fails, and sets errno to EEX-
                  IST.  This flag is ignored for fdopen().
    
           In addition to the above characters, fopen() and freopen() support  the
           following syntax in mode:
    
               ,ccs=string
    
           The  given string is taken as the name of a coded character set and the
           stream is marked as  wide-oriented.   Thereafter,  internal  conversion
           functions  convert  I/O  to  and from the character set string.  If the
           ,ccs=string syntax is not specified, then the wide-orientation  of  the
           stream is determined by the first file operation.  If that operation is
           a wide-character operation, the stream  is  marked  wide-oriented,  and
           functions to convert to the coded character set are loaded.
    
    
    

    BUGS

           When  parsing for individual flag characters in mode (i.e., the charac-
           ters preceding the "ccs" specification), the  glibc  implementation  of
           fopen()  and freopen() limits the number of characters examined in mode
           to 7 (or, in glibc versions before 2.14, to 6, which was not enough  to
           include possible specifications such as "rb+cmxe").  The current imple-
           mentation of fdopen() parses at most 5 characters in mode.
    
    
    

    SEE ALSO

           open(2), fclose(3), fileno(3), fmemopen(3), fopencookie(3)
    
    
    

    GNU 2012-04-22 FOPEN(3)

    
    
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