Operating_System/fun_1.c

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

#include "mytop.c"
//#include "fun.h"


void eval(char *cmdline)
{
    char *argv[MAXLINE];
    char buf[MAXLINE];
    int isBg;
    int pid;
    strcpy(buf,cmdline);
    isBg = parseline(cmdline,argv);
    if(argv[0] == NULL)
    {
	    return;
    }

    if(!builtin_cmd(argv))
    {
        if((pid=fork())==0)
        {
            if(isBg)
            {
                int fd = open( "/dev/null", O_RDWR );
                dup2( fd, 0 );
                dup2( fd, 1 );
                signal(SIGCHLD, SIG_IGN);
            }
            if(execvp(argv[0],argv)<0)
            {
                printf("%s:Command not found.\n",argv[0]);
                exit(0);
            }
        }
        if(!isBg)
        {
            wait(0);
            return;
        }
        else
        {
            signal(SIGCHLD, SIG_IGN);
            return;
        }
    }
}

int parseline(const char *cmdline, char **argv)
{
    static char array[MAXLINE];
    char *buf = array;
    char *delim;
    int argc;
    int bg;

    strcpy(buf, cmdline);
    buf[strlen(buf)-1] = ' ';
    while (*buf && (*buf == ' '))
        buf++;

    argc = 0;
    if (*buf == '\'')
    {
        buf++;
        delim = strchr(buf, '\'');
    }
    else
    {
        delim = strchr(buf, ' ');
    }

    while (delim)
    {
        argv[argc++] = buf;
        *delim = '\0';
        buf = delim + 1;
        while (*buf && (*buf == ' '))
        {
            buf++;
        }

        if (*buf == '\'')
        {
            buf++;
            delim = strchr(buf, '\'');
        }
        else
        {
            delim = strchr(buf, ' ');
        }
    }
    argv[argc] = NULL;

    if (argc == 0)
	    return 1;

    if ((bg = (*argv[argc-1] == '&')) != 0)
    {
        argv[--argc] = NULL;
    }
    return bg;
}

int builtin_cmd(char **argv)
{
    if(Is_pipe(argv)==1)
    {
        return 1;
    }
    if(Is_redirect(argv)==1)
    {
        return 1;
    }
	if(!strcmp(argv[0],"quit")||!strcmp(argv[0],"exit"))
    {
		exit(0);
	}
    if(!strcmp(argv[0],"history"))
    {
        print_history(argv[1]);
		return 1;
	}
    if(!strcmp(argv[0],"cd"))
    {
	    if (argv[1] == NULL)
	    {
	    	return 1;
	    }
	    else
	    {
		    if (chdir(argv[1]) != 0)
		    {
		    	perror("Error: ");
		    }
		    return 1;
	    }
	}
    if(!strcmp(argv[0],"mytop"))
    {
        mytop();
		return 1;
	}
    return 0;
}