Merge pull request #1560 from stwish-msft/patch-10

Update fflush sample

Author: Colin Robertson

docs/c-runtime-library/reference/fflush.md

@@ -1,6 +1,6 @@
 ---
 title: "fflush"
-ms.date: "11/04/2016"
+ms.date: "09/11/2019"
 apiname: ["fflush"]
 apilocation: ["msvcrt.dll", "msvcr80.dll", "msvcr90.dll", "msvcr100.dll", "msvcr100_clr0400.dll", "msvcr110.dll", "msvcr110_clr0400.dll", "msvcr120.dll", "msvcr120_clr0400.dll", "ucrtbase.dll", "api-ms-win-crt-stdio-l1-1-0.dll"]
 apitype: "DLLExport"
@@ -56,44 +56,50 @@ For additional compatibility information, see [Compatibility](../../c-runtime-li
 
 ```C
 // crt_fflush.c
+// Compile with: cl /W4 crt_fflush.c
+// This sample gets a number from the user, then writes it to a file.
+// It ensures the write isn't lost on crash by calling fflush.
 #include <stdio.h>
-#include <conio.h>
 
-int main( void )
+int * crash_the_program = 0;
+
+int main(void)
 {
-   int integer;
-   char string[81];
-
-   // Read each word as a string.
-   printf( "Enter a sentence of four words with scanf: " );
-   for( integer = 0; integer < 4; integer++ )
-   {
-      scanf_s( "%s", string, sizeof(string) );
-      printf( "%s\n", string );
-   }
-
-   // You must flush the input buffer before using gets.
-   // fflush on input stream is an extension to the C standard
-   fflush( stdin );
-   printf( "Enter the same sentence with gets: " );
-   gets_s( string, sizeof(string) );
-   printf( "%s\n", string );
+    FILE * my_file;
+    errno_t err = fopen_s(&my_file, "myfile.txt", "w");
+    if (my_file && !err)
+    {
+        printf("Write a number: ");
+
+        int my_number = 0;
+        scanf_s("%d", &my_number);
+
+        fprintf(my_file, "User selected %d\n", my_number);
+
+        // Write data to a file immediately instead of buffering.
+        fflush(my_file);
+    
+        if (my_number == 5)
+        {
+            // Without using fflush, no data was written to the file 
+            // prior to the crash, so the data is lost.
+            *crash_the_program = 5;
+        }
+
+        // Normally, fflush is not needed as closing the file will write the buffer.
+        // Note that files are automatically closed and flushed during normal termination.
+        fclose(my_file);
+    }
+    return 0;
 }
 ```
 
 ```Input
-This is a test
-This is a test
+5
 ```
 
-```Output
-Enter a sentence of four words with scanf: This is a test
-This
-is
-a
-test
-Enter the same sentence with gets: This is a test
-This is a test
+```myfile.txt
+User selected 5
 ```
 
 ## See also