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diff --git a/reference/C/CONTRIB/SNIP/isshare.c b/reference/C/CONTRIB/SNIP/isshare.c
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+++ b/reference/C/CONTRIB/SNIP/isshare.c
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+/*
+** 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.
+**
+** Example of usage:
+**
+** main(int argc, char *argv[])
+** {
+**   int sharing;
+**
+**   sharing = is_share(argv[0]);
+**   .
+**   .
+**   if (sharing)
+**   {
+**     // open file in shared mode
+**     ...
+**   }
+**   else
+**   {
+**     // use "normal" open
+**     ...
+**   }
+** }
+**
+** Revision History:
+**
+** 08/03/93  Original:  "is_sharing()" by Mike Ratledge of fidonet
+** 10/20/93  Revision:  revised for library
+** 04/03/94  Revision:  "Portabalized" for SNIPPETS by Bob Stout
+*/
+
+#include <stdio.h>
+#include <io.h>
+#include <dos.h>
+
+#if defined(_MSC_VER)
+ #include <stdlib.h>
+ #include <sys\locking.h>
+
+ int lock(int fp, long ofs, long lng)
+ {
+       lseek(fp,0L,SEEK_SET);
+       return locking(fp,LK_LOCK,lng);
+ }
+
+ int unlock(fp,ofs,lng)
+ {
+       lseek(fp,0L,SEEK_SET);
+       return locking(fp,LK_UNLCK,lng);
+ }
+#endif
+
+int is_share(char *arg)
+{
+      FILE *exe;
+
+      if (_osmajor < 3)
+            return(0);
+
+      exe = fopen(arg, "rb");
+
+      if (0 == lock(fileno(exe), 0l, 500l))
+      {
+            unlock(fileno(exe), 0l, 500l);
+            fclose(exe);
+            return(1);
+      }
+
+      fclose(exe);
+      return(0);
+}