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ISSHARE.C
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1996-11-24
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/* +++Date last modified: 28-Sep-1996 */
/*
** is_share() - This is a routine that allows a program to determine
** if file-sharing is enabled at run-time.
**
** What does this code do? First - it checks to make sure
** it is running under DOS 3.0+ - otherwise - no sharing.
** Next, it opens the program itself (the .EXE file) by using
** "argv[0]". This argument points to the actual program name
** complete with the path under DOS 3.0 or later. It then
** attempts to lock the first 500 bytes of the program on
** disk. If successful (i.e. return != -1), it unlocks the
** locked bytes and closes the file (actually the unlock is
** superfluous since closing the file releases all locks) and
** returns the a "TRUE" (1) result. If it fails, it closes
** the .EXE file and returns a "FALSE" (0) result. Note that
** this does not depend on opening a file in shared mode to
** test it.
**
** Revision History:
**
** 08/03/93 Original: "is_sharing()" by Mike Ratledge of fidonet
** 10/20/93 Revision: revised for library
** 04/03/94 Revision: "Portabilized" for SNIPPETS by Bob Stout
*/
#include <stdio.h>
#include <io.h>
#include <dos.h>
#include "snpdosys.h"
#include "errors.h"
#if !defined(__TURBOC__)
#include <stdlib.h>
#include <sys\locking.h>
int lock(int fp, long ofs, long lng)
{
lseek(fp,ofs,SEEK_SET);
return locking(fp,LK_LOCK,lng);
}
int unlock(int fp, long ofs, long lng)
{
lseek(fp,ofs,SEEK_SET);
return locking(fp,LK_UNLCK,lng);
}
#endif
int is_share(char *arg)
{
FILE *exe;
if (_osmajor < 3)
return(0);
exe = cant(arg, "rb");
if (0 == lock(fileno(exe), 0L, 500L))
{
unlock(fileno(exe), 0L, 500L);
fclose(exe);
return(1);
}
fclose(exe);
return(0);
}
#ifdef TEST
#ifdef __WATCOMC__
#pragma off (unreferenced);
#endif
#ifdef __TURBOC__
#pragma argsused
#endif
main(int argc, char *argv[])
{
int sharing = is_share(argv[0]);
printf("File sharing is%s enabled\n", sharing ? "" : " not");
return 0;
}
#endif /* TEST */