1 files changed, 71 insertions, 0 deletions
diff --git a/parent_to_child.c b/parent_to_child.c
new file mode 100644
index 0000000..c0c0695
--- /dev/null
+++ b/parent_to_child.c
@@ -0,0 +1,71 @@
+/* dup.c
+ *
+ * Parent piping to a child where child spawns using new stdin
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <wait.h>
+
+extern char **environ;
+
+int main(int argc, char **argv)
+{
+    pid_t pid;
+    int stat_loc;
+
+    char *str = "all base are belong to us";
+    int pfds[2];
+    int ret;
+
+    if (pipe(pfds) == 0)
+    {
+        pid = fork();
+        if (pid == -1)
+        {
+            perror("fork");
+            exit(EXIT_FAILURE);
+        }
+
+        if (pid) /* parent */
+        {
+            close(1);         /* break the link to stdout, dup2 already kills this but meh */
+            dup2(pfds[1], 1); /* redirect stdout to pfds[1] */
+            close(pfds[1]);   /* new stdout has been setup above, pfds[1] can be closed */
+            close(pfds[0]);   /* parent will not be reading anything from out pipe */
+
+            printf("parent sends out: \"%s\"\n", str);
+            fflush(stdout);   /* printf is buffered! */
+            close(1);         /* close stdin or else the child would not know that he's done reading */
+
+            ret = waitpid(pid, &stat_loc, WCONTINUED);
+        }
+        else /* child */
+        {
+            close(0);         /* break the link to stdin */
+            dup2(pfds[0], 0); /* redirect stdin to pfds[0] */
+            close(pfds[0]);   /* new stdin has been setup above, pfds[1] can be closed */
+            close(pfds[1]);   /* parent will not be writing anything into our pipe */
+
+            /* here the child will use a redefined stdin */
+            execlp("wc", "wc", NULL);
+            /* if there wasn't a spawn then we would need to close stdin */
+        }
+    }
+    else
+    {
+        perror("pipe");
+        exit(EXIT_FAILURE);
+    }
+
+    ret = ret; /* hush the dumb compiler */
+
+    close(pfds[0]);
+    close(pfds[1]);
+
+    return 0;
+}
+