From 569f4b11e5d46ba1b8a557f1fbbed7e225280f92 Mon Sep 17 00:00:00 2001
From: Brandon Rodriguez <brodriguez8774@gmail.com>
Date: Thu, 19 Oct 2017 17:02:06 -0400
Subject: [PATCH] Add another example program
---
Examples/DupExecDemo.c | 53 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
create mode 100644 Examples/DupExecDemo.c
diff --git a/Examples/DupExecDemo.c b/Examples/DupExecDemo.c
new file mode 100644
index 0000000..9e3c95c
--- /dev/null
+++ b/Examples/DupExecDemo.c
@@ -0,0 +1,53 @@
+// This code is intended to demo small pieces of code relevant to a shell
+// dup2, execv() in particular
+// In addition, the most useful makeargv() method will be used
+
+//#include "makeargv.h"
+#include <stdio.h>
+#include "apue.h"
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h> // OverKill
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <string.h>
+
+int makeargv(char *, char *, char ***);
+
+
+int main() {
+ int NewFD;
+ int i;
+ int j;
+ char ** ExecVectors;
+
+ write(STDOUT_FILENO, "To Console\n", 11);
+
+ // Now open a file and get a file descriptor
+ mode_t mode = S_IRUSR | S_IWUSR | S_IXUSR; // FOR OPEN AND CREATE OF FILES
+ int oflag = O_CREAT | O_RDWR | O_TRUNC;
+
+ NewFD = open("DummyFile", oflag, mode); //just making a file
+ printf("DummyFile descriptor is %u\n", NewFD); //printing to STDOUT
+
+ NewFD = dup2(NewFD, STDOUT_FILENO); //now STDOUT is pointing to the file
+ printf("Dup File descriptor is %u\n", NewFD); //printing to STDOUT
+ //that is redirected to file
+
+ write(STDOUT_FILENO, "To Console ?\n", 13); //no, to the file
+
+ /////////////////////////////////////////////////////////////////////////////
+ //Now lets mess with executing things
+
+ j = makeargv(" \nls -l / | cat DupExecDemo.c ? ls -l . ", "\t \n", &ExecVectors);
+ //^^^^^^^^( command delimeters start of command
+ //returns number of tokens, which is 6
+
+ for (i = 0; i < j; i++)
+ fprintf(stderr, "%s\n", ExecVectors[i]); //stderr finds its way to
+ //console anyway
+
+ ExecVectors[3] = NULL;ExecVectors[6]=NULL;
+ execvp(ExecVectors[7], &ExecVectors[7]);
+}
--
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