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+Return to [[os:|Operationg Systems home]]
+----
+====== Operating Systems Course: Lab03 ======
+===== Laboratory number 03 =====
+==== Exercise 01: System call fork, exec, system ====
+Report the //control flow graph// (CFG) and the //process generation tree// for the following C program.
+In addition, indicate what it produces in output on the screen and for which reason.
+<code c lab04_e01.c>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+int main () {
+  char str[100];
+  int i;
+  setbuf(stdout,0);
+  fork();
+  for (i=0; i<2; i++){
+    if (fork()!=0) {
+      sprintf (str, "echo system with i=%d", i);
+      system (str);
+    } else {
+      sprintf (str, "exec with i=%d", i);
+      execlp ("echo", "myPgrm", str, NULL);
+    }
+  }
+  return (0);
+}
+</code>
+==== Exercise 02: System call fork, exec, system ====
+Report the //control flow graph// (CFG) and the //process generation tree// for the following C program.
+In addition, indicate what it produces in output on the screen and for which reason.
+<code c lab04_e02.c>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+int main () {
+  int i = 0;
+  setbuf(stdout,0);
+  while (i<=2 && fork()){
+    if (!fork()) {
+      fprintf (stdout, "Running Exec ...");
+      execlp ("echo", "echo", "i*i", (char *) 0);
+    }
+    i++;
+    fprintf (stdout, "Running System ...");
+    system ("echo i+i");
+  }
+  return (0);
+}
+</code>
+==== Exercise 03: System call fork, wait, exec, system ====
+A file contains strings logically grouped into distinct sets.
+Any set of strings indicates a Unix/Linux command and the related parameters.
+Each set is terminated with the string "end".
+The following is an example of correct file:
+<code bash commands.txt>
+touch mioFile.c end
+ls -laR end
+cat mioFile.c end
+mkdir -p tmpDir end
+cp -f mioFile.c tmpDir end
+</code>
+Observe that, if you prefer, you can assume that the string "end" is not present in the file, and it can be substituted with the end-of-line character ''\n'' to indicate the end of the strings associated with a certain command.
+Write a program that, after receiving the name of the file through the command line, executes the Unix/Linux command listed in the file by using:
+  * the system call ''system'', executing one command after another
+  * the system call ''exec'', executing a command every 3 seconds (you can decide with version of the ''exec'' to use).

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