UNIX for Dummies Questions & Answers

/* RCS information: $Id: myshell.c,v 1.2 2006/04/05 22:46:33 elm Exp $ */
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
extern char **getline();
/*Run command with and without arguments*/
void runc(const char *n, char *av[]){
 pid_t pid;
 int status;
 pid=fork();
 if (pid == 0) {
  /* Child */
         execvp(n,av);
                perror("You print wrong command");
  exit(-1);
 }
 else {
  /* Parent */
  wait(&status);
 }
}
void out(const char *n, char *av[]){
   int fd;
 fd = open("outf", O_WRONLY|O_CREAT); 
 if (fd < 0) {
  fprintf(stderr, "Couldn't open file for writing.\n");
 }
 dup2(fd, 1);
 /*execvp("ls",args);*/
 /*{execvp(n,av);}*/
 runc(n,av);
 close(fd);
}
int main() {
  int i;
  char **args; 
  pid_t pid;
  int status;

  while(1) {
    printf("$ ");
    args = getline();
    for(i = 0; args[i] != NULL; i++) {
      printf("Argument %d: %s\n", i, args[i]);
    }
  
 /*Exit command to terminate shell */
 if (strcmp(args[0],"exit")==0)
  exit();
 /*Run command with and without arguments*/
 /*{runc(args[0],args);*/
 out(args[0],args);
  }
 return 0;
}

gcc -g -o myshell myshell.c

gdb myshell core
appworx> gdb myshell core
GNU gdb 5.3
Copyright 2002 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "sparc-sun-solaris2.9"...

Core was generated by `./myshell '.
Program terminated with signal 11, Segmentation fault.
#0  0x00000000 in ?? ()
(gdb) ba
#0  0x00000000 in ?? ()
#1  0x000111f8 in dt_arithmetic (fmt=0xffbfedf0 "+%s", d_value=0, sec=0, chg_tim=0) at add_time.c:150
#2  0x00011710 in process (p=0xffbff23e "0", ptr=0, fmtptr=0xffbfedf0 "+%s") at add_time.c:242
#3  0x0001191c in main (argc=4, argv=0xffbff064) at add_time.c:272
(gdb)