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fopen()                   STDIO Function                  fopen()




Open a stream for standard I/O

#include <stdio.h>
FFIILLEE *ffooppeenn (_n_a_m_e, _t_y_p_e) cchhaarr *_n_a_m_e, *_t_y_p_e;

fopen  allocates and  initializes  a FILE  structure, or  stream;
opens  or creates  the file  name; and returns  a pointer  to the
structure for  use by other  STDIO routines.  name  refers to the
file to be opened.  type is a string that consists of one or more
of the characters ``rwa'', to indicate the mode of the string, as
follows:


             rr       Read; error if file not found
             ww       Write; truncate if found, create if not found



             aa       Append to end of file; no truncation, create if not found
             rr+      Read and write; no truncation, error if not found



             ww+      Write and read; truncate if found, create if not found
             aa+      Append and read; no truncation, create if not found


The modes that  contain `a' set the seek pointer  to point at the
end of the file; all other modes set it to point at the beginning
of  the  file.   Modes that  contain  `+'  both  read and  write;
however, a  program must call ffsseeeekk or  rreewwiinndd before it switches
from reading to writing or vice versa.

***** Example *****  This example copies argv[1] to argv[2] using
STDIO  routines.   It demonstrates  the  functions fopen,  fread,
fwrite, fclose, and feof.


#include <stdio.h>
/* BUFSIZ is defined in stdio.h */
char buf[BUFSIZ];



void fatal(message)
char *message;
{
        fprintf(stderr, "copy: %s\n", message);
        exit(1);
}






COHERENT Lexicon                                           Page 1




fopen()                   STDIO Function                  fopen()



main(argc, argv)
int argc; char *argv[];
{
        register FILE *ifp, *ofp;
        register unsigned int n;



        if (argc != 3)
                fatal("Usage: copy source destination");
        if ((ifp = fopen(argv[1], "r")) == NULL)
                fatal("cannot open input file");
        if ((ofp = fopen(argv[2], "w")) == NULL)
                fatal("cannot open output file");



        while ((n = fread(buf, 1, BUFSIZ, ifp)) != 0) {
                if (fwrite(buf, 1, n, ofp) != n)
                        fatal("write error");
        }



        if (!feof(ifp))
                fatal("read error");
        if (fclose(ifp) == EOF || fclose(ofp) == EOF)
                fatal("cannot close");
        exit(0);
}


***** See Also *****

fclose(), fdopen(), freopen(), STDIO

***** Diagnostics *****

fopen returns NULL if it cannot allocate a FILE structure, if the
type string is  nonsense, or if the call to  open or creat fails.
Currently, only 20  FILE structures can be allocated per program,
including stdin, stdout, and stderr.

***** Notes *****

Many operating systems recognize a `b' modifier to the type argu-
ment; this  indicates that the file  contains binary information,
and lets  the operating  system handle ``funny  characters'' cor-
rectly.  COHERENT has  no need of such a modifier,  so if you ap-
pend `b' to type, it will be ignored.  This modifier, however, is
recognized by numerous other operating systems, including MS-DOS,
OS/2, and GEMDOS.  If you expect to port developed code to any of
these operating systems, files should append the `b' to type.




COHERENT Lexicon                                           Page 2

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