shell-0.0.7.c

#include  <stdio.h>
#include  <sys/types.h>
#include <stdlib.h>

void  parse(char *line, char **argv)
{
     while (*line != '\0') {       /* if not the end of line ....... */ 
          while (*line == ' ' || *line == '\t' || *line == '\n')
               *line++ = '\0';     /* replace white spaces with 0    */
          *argv++ = line;          /* save the argument position     */
          while (*line != '\0' && *line != ' ' && 
                 *line != '\t' && *line != '\n') 
               line++;             /* skip the argument until ...    */
     }
     *argv = '\0';                 /* mark the end of argument list  */
}
     
void  execute(char **argv)
{
     pid_t  pid;
     int    status;
     
     if ((pid = fork()) < 0) {     /* fork a child process           */
          printf("*** ERROR: forking child process failed\n");
          exit(1);
     }
     else if (pid == 0) {          /* for the child process:         */
          if (execvp(*argv, argv) < 0) {     /* execute the command  */
               printf("*** ERROR: exec failed\n");
               exit(1);
          }
     }
     else {                                  /* for the parent:      */
          while (wait(&status) != pid)       /* wait for completion  */
               ;
     }
}

void  main(void)
{
	char *line = NULL;
	size_t len = 0;
	ssize_t read;
	char  **argv;

	while ((read = getline(&line, &len, stdin)) != -1) 
	{
		parse(line, argv);       /*   parse the line               */
		execute(argv);           /* otherwise, execute the command */
	}

	free(line);
	free(argv);
	

	return 0;	
}