1 files changed, 91 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/OR_USING_C/09.4.c b/reference/C/CONTRIB/OR_USING_C/09.4.c
new file mode 100644
index 0000000..dba1cd6
--- /dev/null
+++ b/reference/C/CONTRIB/OR_USING_C/09.4.c
@@ -0,0 +1,91 @@
+/*
+ * mailer - open a pipe to the mail command and send the user
+ *          mail.
+ */
+#include <stdio.h>
+
+main()
+{
+    FILE *fp;
+    int pid, pipefds[2];
+    char *username, *getlogin();
+
+    /*
+     * Get the user's name.
+     */
+    if ((username = getlogin()) == NULL) {
+        fprintf(stderr, "Who are you?\n");
+        exit(1);
+    }
+
+    /*
+     * Create the pipe.  This has to be done
+     * BEFORE the fork.
+     */
+    if (pipe(pipefds) < 0) {
+        perror("pipe");
+        exit(1);
+    }
+
+    if ((pid = fork()) < 0) {
+        perror("fork");
+        exit(1);
+    }
+
+    /*
+     * The child process executes the stuff inside
+     * the if.
+     */
+    if (pid == 0) {
+        /*
+         * Make the read side of the pipe our
+         * standard input.
+         */
+        close(0);
+        dup(pipefds[0]);
+        close(pipefds[0]);
+
+        /*
+         * Close the write side of the pipe;
+         * we'll let our output go to the screen.
+         */
+        close(pipefds[1]);
+
+        /*
+         * Execute the command "mail username".
+         */
+        execl("/bin/mail", "mail", username, 0);
+        perror("exec");
+        exit(1);
+    }
+
+    /*
+     * The parent executes this code.
+     */
+
+    /*
+     * Close the read side of the pipe; we
+     * don't need it (and the child is not
+     * writing on the pipe anyway).
+     */
+    close(pipefds[0]);
+
+    /*
+     * Convert the write side of the pipe to stdio.
+     */
+    fp = fdopen(pipefds[1], "w");
+
+    /*
+     * Send a message, close the pipe.
+     */
+    fprintf(fp, "Hello from your program.\n");
+    fclose(fp);
+
+    /*
+     * Wait for the process to terminate.
+     */     
+    while (wait((int *) 0) != pid)
+        ;
+
+    exit(0);
+}