Added example program.

man2/pipe.2

@@ -60,6 +60,62 @@ Too many file descriptors are in use by the process.
 The system limit on the total number of open files has been reached.
 .SH "CONFORMING TO"
 POSIX.1
+.SH EXAMPLE
+The following program creates a pipe, and then 
+.BR fork (2)s 
+to create a child process.  
+After the 
+.BR fork (2),
+each process closes the descriptors that it doesn't need for the pipe
+(see 
+.BR pipe (7)).
+The parent then writes the string contained in the program's 
+command-line argument to the pipe, 
+and the child reads this string a byte at a time from the pipe 
+and echoes it on standard output.
+.nf
+
+#include <sys/wait.h>
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+
+int
+main(int argc, char *argv[])
+{
+    int pfd[2];
+    pid_t cpid;
+    char buf;
+
+    assert(argc == 2);
+
+    if (pipe(pfd) == -1) { perror("pipe"); exit(EXIT_FAILURE); }
+
+    cpid = fork();
+    if (cpid == -1) { perror("fork"); exit(EXIT_FAILURE); }
+
+    if (cpid == 0) {    /* Child reads from pipe */
+        close(pfd[1]);          /* Close unused write end */
+
+        while (read(pfd[0], &buf, 1) > 0)
+            write(STDOUT_FILENO, &buf, 1);
+
+        write(STDOUT_FILENO, "\\n", 1);
+        close(pfd[0]);
+        _exit(EXIT_SUCCESS);
+
+    } else {            /* Parent writes argv[1] to pipe */
+        close(pfd[0]);          /* Close unused read end */
+        write(pfd[1], argv[1], strlen(argv[1]));
+        close(pfd[1]);          /* Reader will see EOF */
+        wait(NULL);             /* Wait for child */
+        exit(EXIT_SUCCESS);
+    }
+}
+
+.fi
 .SH "SEE ALSO"
 .BR fork (2),
 .BR read (2),