FOPEN(3S)               GENIX Programmer's Manual               FOPEN(3S)



      NAME
           fopen, freopen, fdopen - open a stream

      SYNOPSIS
           #include <stdio.h>

           FILE *fopen(filename, type)
           char *filename, *type;

           FILE *freopen(filename, type, stream)
           char *filename, *type;
           FILE *stream;

           FILE *fdopen(fildes, type)
           char *type;

      DESCRIPTION
           Fopen opens the file named by filename and associates a stream  with
           it.   Fopen  returns  a pointer to be used to identify the stream in
           subsequent operations.

           Type is a character string having one of the following values:

           "r"  open for reading

           "w"  create for writing

           "a"  append: open for writing at end of file, or create for writing

           In addition, each type may be followed by a '+'  to  have  the  file
           opened  for  reading  and writing.  "r+" positions the stream at the
           beginning of the file, "w+" creates or truncates it, and "a+"  posi-
           tions  it  at  the  end.   Both  reads  and  writes  may  be used on
           read/write streams, with the limitation that an  fseek,  rewind,  or
           reading  an  end-of-file  must be used between a read and a write or
           vice-versa.

           Freopen substitutes the named file in place of the open stream.   It
           returns  the  original  value  of  stream.   The  original stream is
           closed.

           Freopen is typically used to attach the  preopened  constant  names,
           stdin, stdout, stderr, to specified files.

           Fdopen associates a stream with  a  file  descriptor  obtained  from
           open,  dup,  creat,  or  pipe(2).  The type of the stream must agree
           with the mode of the open file.

      SEE ALSO
           open(2), fclose(3)





      Printed 11/16/83                                                        1

      FOPEN(3S)               GENIX Programmer's Manual               FOPEN(3S)



      DIAGNOSTICS
           Fopen and freopen return the pointer  NULL  if  filename  cannot  be
           accessed.

      BUGS
           Fdopen is not portable to systems other than UNIX.

           The read/write types do not exist on  all  systems.   Those  systems
           without  read/write modes will probably treat the type as if the '+'
           was not present.













































      Printed 11/16/83                                                        2