Create pipe_execl.c

Modeling the command-line command:  ps -ef | wc  using pipes.

Author: holman57

Diff for: pipe_execl.c

@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+enum {READ, WRITE};
+
+int main()
+{
+    int fd[2];
+
+    if (pipe(fd) == -1)
+    {
+        perror("Pipe");
+        exit(1);
+    }
+
+    switch (fork())
+    {
+        case -1:
+            perror("Fork");
+            exit(2);
+
+        case 0:
+            // Child
+
+            // The function fileno() examines the argument
+            // stream and returns its integer descriptor.
+            dup2(fd[WRITE], fileno(stdout));
+            close(fd[READ]);
+            close(fd[WRITE]);
+
+            // int execl(const char *path, const char *arg0, ..., const char *argn, (char *)0);
+            execl("/bin/ps", "ps", "-ef", (char *) 0);
+            exit(3);
+
+        default:
+            // Parent
+
+            dup2(fd[READ], fileno(stdin));
+            close(fd[READ]);
+            close(fd[WRITE]);
+
+            execl("/usr/bin/wc", "wc", (char *) 0);
+            exit(4);
+    }
+
+    return 0;
+}
+