fdopen(3C)




NAME

     fdopen - associate a stream with a file descriptor


SYNOPSIS

     #include <stdio.h>

     FILE *fdopen(int fildes, const char *mode);


DESCRIPTION

     The fdopen()  function  associates  a  stream  with  a  file
     descriptor fildes.

     The mode argument is a character string having  one  of  the
     following values:

     r or rb               Open a file for reading.
     w or wb               Open a file for writing.
     a or ab               Open a file for writing  at  end  of
                           file.
     r+ or rb+ or r+b      Open a file for update (reading  and
                           writing).
     w+ or wb+ or w+b      Open a file for update (reading  and
                           writing).
     a+ or ab+ or a+b      Open a file for update (reading  and
                           writing) at end of file.

     The meaning of these flags is exactly as specified  for  the
     fopen(3C)  function,  except  that modes beginning with w do
     not cause truncation of the file.

     The mode of the stream must be allowed by  the  file  access
     mode  of  the open file. The file position indicator associ-
     ated with the new stream is set to the position indicated by
     the file offset associated with the file descriptor.

     The fdopen() function preserves the  offset  maximum  previ-
     ously  set  for  the  open file description corresponding to
     fildes.

     The error and end-of-file  indicators  for  the  stream  are
     cleared.  The fdopen() function may cause the st_atime field
     of the underlying file to be marked for update.

     If fildes refers to a shared memory object,  the  result  of
     the fdopen() function is unspecified.


RETURN VALUES

     Upon successful completion, fdopen() returns a pointer to  a
     stream.  Otherwise,  a null pointer is returned and errno is
     set to indicate the error.

     The fdopen() function may fail and not set  errno  if  there
     are no free stdio streams.


ERRORS

     The fdopen() function may fail if:

     EBADF The fildes argument is not a valid file descriptor.

     EINVAL
           The mode argument is not a valid mode.

     EMFILE
           The number of streams currently open  in  the  calling
           process is either FOPEN_MAX or STREAM_MAX.

     ENOMEM
           Insufficient space to allocate a buffer.


USAGE

     The number of streams that a process can have  open  at  one
     time  is  STREAM_MAX.  If  defined, it has the same value as
     FOPEN_MAX.

     File descriptors  are  obtained  from  calls  like  open(2),
     dup(2),  creat(2)  or  pipe(2),  which open files but do not
     return streams. Streams are necessary input for  almost  all
     of the Section 3S library routines.


ATTRIBUTES

     See attributes(5) for descriptions of the  following  attri-
     butes:

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | MT-Level                    | MT-Safe                     |
    |_____________________________|_____________________________|


SEE ALSO

     creat(2), dup(2), open(2), pipe(2),  fclose(3C),  fopen(3C),
     attributes(5)


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