Programming

#include <stdio.h>

/* These are useful to keep the source readable */
#ifndef STDIN_FILENO
# define STDIN_FILENO 0
#endif
#ifndef STDOUT_FILENO
# define STDOUT_FILENO 1
#endif
#ifndef STDERR_FILENO
# define STDERR_FILENO 2
#endif
#ifndef SHUT_RDWR
# define SHUT_RDWR 2
#endif

char *opt_exec = NULL;  /* program to exec after connecting */
static void ncexec(FILE *MyOutput)
{
  int saved_stderr;
  char *p;
 // assert(ncsock && (ncsock->fd >= 0));
  /* save the stderr fd because we may need it later */
  saved_stderr = dup(STDERR_FILENO);
  /* duplicate the socket for the child program */
  dup2(MyOutput, STDIN_FILENO); /* the precise order of fiddlage */
  close(MyOutput);   /* is apparently crucial; this is */
  dup2(STDIN_FILENO, STDOUT_FILENO); /* swiped directly out of "inetd". */
  dup2(STDIN_FILENO, STDERR_FILENO); /* also duplicate the stderr channel */
  /* change the label for the executed program */
  if ((p = strrchr(opt_exec, '/')))
    p++;   /* shorter argv[0] */
  else
    p = opt_exec;
  /* replace this process with the new one */
#ifndef USE_OLD_COMPAT
  execl("/bin/sh", p, "-c", opt_exec, NULL);
#else
  execl(opt_exec, p, NULL);
#endif
  dup2(saved_stderr, STDERR_FILENO);
//  ncprint(NCPRINT_ERROR | NCPRINT_EXIT, _("Couldn't execute %s: %s"),
 //  opt_exec, strerror(errno));
}    /* end of ncexec() */
int main()
{
 FILE *fOutput;
 fOutput = fopen("/mnt/hgfs/VMShares/output.txt", "w+");
 if (fOutput == NULL) printf("fOutput Error\n");
 if (fork() == 0)
 {
  printf("Fork() Success !\n");
  ncexec(fOutput);
 }
 sleep(2);
 //fwrite("ls", 4, 2, fOutput);
 return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char **argv)
{
   FILE *cmd=NULL;                          // FILE* for popen
   char tmp[2048]={0x0};                    // string for input/output
   for(;;)                                  // loop forever (see exit below)
   {
      printf("Enter a command(exit to quit): ");
      fflush(stdout);                        //prompt to display
      fgets(tmp, sizeof(tmp), stdin);        // read answer 
      if (strcmp(tmp, "exit\n")==0 )         // if exit then exit program
           exit(0);        
      cmd=popen(tmp,"r");                    // open a command via popen
      while(fgets(tmp, sizeof(tmp), cmd)!=NULL) // display results
           printf("%s", tmp);
      pclose(cmd);                           // close the popen stream
   } 
   return 0;                                 // never reached
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
int main(int argc, char **argv)
{
   FILE *cmd=NULL;                          // FILE* for popen
   char tmp[2048]={0x0};                    // string for input/output
   cmd=popen("xterm","r");                    // open a command via popen
   for(;;)                                  // loop forever (see exit below)
   {
      printf("Enter a command(exit to quit): ");
      fflush(stdout);                        //prompt to display
      fgets(tmp, sizeof(tmp), stdin);        // read answer
      if (strcmp(tmp, "exit\n")==0 )         // if exit then exit program
           exit(0);
      pwrite(cmd, tmp, sizeof(tmp), 0);
      pwrite(cmd, "\n", 1, 0);
      while(fgets(tmp, sizeof(tmp), cmd)!=NULL) // display results
           printf("%s", tmp);
   //   pclose(cmd);                           // close the popen stream
   }
   return 0;                                 // never reached
}