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From: dedreb@arco.com (Richard Beecher)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Numbers from TEXT files under Think C ?
Message-ID: <1991Apr22.163030.17480@Arco.COM>
Date: 22 Apr 91 16:30:30 GMT
References: <17150002@hpihoah.cup.hp.com>
Sender: news@Arco.COM
Distribution: usa
Organization: Arco Alaska
Lines: 56

In article <17150002@hpihoah.cup.hp.com> cring@hpihoah.cup.hp.com (Craig Ring)
writes:
>I am writing a program in Think C 4.0 that needs to read numeric input from
>an ASCII text file.  Under UNIX this is very easy to do with fscanf() and so
>on.  Is there a simple way to do this with a Macintosh?  
>
>I would like to be able to use SFGetFile() to allow the user to pick the
>file they would like to open, but the SFReply doesn't seem to be very useful
>to the ANSI C libraries for Think C.  The Think C documentation says that
>scanf() requires a pointer to type FILE, which I am not sure how to get.
>
>I could of course write my own routines to use the Toolbox calls to read
>data from the file, and then convert the ASCII character codes to a numeric
>data type, but this seems like a lot of work compared to using library
>routines to do it for me.
>
>Any help you can give me would be greatly appreciated.
>
>Craig Ring
>cring@leland.stanford.edu
>

First of all, you might want to check out Technical Note #246, entitled "Mixing
HFS and C File I/O".  

I like to use the standard C functions to do a lot of my I/O, too.  Here's some
pseudo code that demonstrates the approach:


GetVol( NULL, &curVRefNum );        /* save the vRefNum */

SFGetFile( loc, etc....., reply );
if ( !reply.good ) break;           /* or return, or whatever */
SetVol( NULL,reply.vRefNum );

PtoCstr( (char *) &reply.fName );
filePtr = fopen( (char *) reply.fName, "r" );
if ( filePtr == NULL ) do whatever....
.
.
read from the file, or whatever
using C libraries (fscanf, fgets, etc.)
.
.
fclose( filePtr );
SetVol( NULL, curVRefNum );        /* restore the previous vRefNum */


Setting the default volume with SetVol( NULL, reply.vRefNum ) allows you to use
the standard C functions to open the file (with fopen).  Good luck, and don't
trust my syntax above! :-)

---------------
Richard Beecher
dedreb@arco.com
---------------