my_shell.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <pwd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <dirent.h>
#include <readline/readline.h>
#include <readline/history.h>

#define COLOR_BAGIN   "\001\033[31m\002"//强调，加粗，高亮
#define COLOR_BAGIN2  "\001\033[34m\002"
#define COLOR_END "\001\033[0m\002"
#define COLOR_BKG_SEF(x,y) "\001\033["#x";"#y"m\002"

static char *ar = (char *)NULL;
static char *arg = (char *)NULL;
int cont[4];


int chazhao(char *str)
{
    DIR *dir;
    struct dirent *dirp;
    char *path[] = {"./", "/bin", "/usr/bin", NULL};

    //使当前目录下的程序可以运行，如命令“./fork”可以被正确解释和执行
    if( strncmp(str, "./", 2) == 0 )
    {
        str = str + 2;
    }

    //分别在当前目录，/bin和/usr/bin目录查找要执行的程序
    int i = 0;
    while(path[i] != NULL)
    {
        if( (dir= opendir(path[i])) ==NULL )
        {
            printf("can not open /bin \n");
        }
        while( (dirp = readdir(dir)) != NULL )
        {
            if(strcmp(dirp->d_name, str) == 0)
            {
                closedir(dir);
                return 1;
            }
        }
        closedir(dir);
        i++;
    }
    return 0;
}

void tj(char **arg)
{
    char *file;
    memset(cont, 0, sizeof(int)*4);
    int i = 0,sum,j = 0,k = 1,fd,sun = 0;
    int *status = NULL,*status2 = NULL,fd2,pid2;
    pid_t pid;
    while(arg[j] != NULL)
    {
        i = 0;
        while(arg[j][i] != '\0')
        {
            if(arg[j][i] == '<')
            {
                cont[0]++;
            }
            if(arg[j][i] == '>')
            {
                cont[1]++;
            }
            if(arg[j][i] == '|')
            {
                cont[2]++;
            }
            if(arg[j][i] == '&')
            {
                arg[j][i] = '\0';
                cont[3]++;
            }
            i++;
        }
        if(cont[0] + cont[1] + cont[2] + cont[3] > 0 && sun == 0)   //找到第一次出现重定向符和管道符位置
        {
            sun = cont[0] + cont[1] + cont[2] + cont[3];
            k = j;
        }
        j++;
    }
    sum = cont[0] + cont[1] + cont[2] + cont[3];
    if(sum != sun)
    {
        printf("命令错误\n");
        return ;
    }
    if(sum == cont[3])
    {
        sum = 0;
    }
    if((arg[0] != NULL) && (strcmp(arg[0], "cd") == 0))
    {
        if(arg[1] == NULL)
        {
            return ;
        }
        if(strcmp(arg[1], "~") == 0)                         //cd ~回到用户目录
        {
            strcpy(arg[1], "/home/ycl/");
        }
        if(chdir(arg[1]) ==  -1)                             //chdir将当前工作目录该为参数工作目录
        {
            perror("cd");
        }
        return ;
    }

    pid = fork();         //子进程先运行
    if(sum == 0)
    {
        if(pid == 0)
        {
            if(chazhao(arg[0]) == 0)
            {
                printf("%s: no input files\n",arg[0]);
                exit(1);
            }
            execvp(arg[0], arg);
        }
    }
    if(sum == cont[0] && cont[0] == 1)          //只有一个输入重定向符 <
    {
        if(pid == 0)
        {
            file = arg[k+1];
            arg[k] = NULL;
            if(chazhao(arg[0]) == 0)
            {
                printf("%s: no input files",arg[0]);
                exit(1);
            }
            fd = open(file, O_RDONLY);
            dup2(fd,0);
            execvp(arg[0], arg);
        }
    }
    if(sum == cont[1] && cont[1] == 1)           //只有一个输出重定向符 >
    {
        if(pid == 0)
        {
            file = arg[k+1];
            arg[k] = NULL;
            if(chazhao(arg[0]) == 0)
            {
                printf("%s: no input files",arg[0]);
                exit(1);
            }
            fd = open(file,O_RDWR | O_CREAT | O_TRUNC, 0644);
            dup2(fd, 1);
            execvp(arg[0], arg);
        }
    } 
    if(sum == cont[1] && cont[1] == 2)           //有两个输出重定向符 >>
    {
        if(pid == 0)
        {
            file = arg[k+1];
            arg[k] = NULL;
            if(chazhao(arg[0]) == 0)
            {
                printf("%s: no input files",arg[0]);
                exit(1);
            }
            fd = open(file,O_RDWR | O_CREAT | O_APPEND);
            dup2(fd,1);
            execvp(arg[0], arg);
        }
    }
    if(sum == cont[2] && cont[2] == 1)           //只有一个管道符 |
    {
        if (pid == 0)
        {
            if( (pid2 = fork()) < 0 )
            {
                printf("创建进程2失败\n");
                return ;
            }
            else if(pid2 == 0)
            {
                arg[k] = NULL;
                if(chazhao(arg[0]) == 0)
                {
                    printf("%s: no input files",arg[0]);
                    exit(1);
                }
                fd2 = open("text", O_WRONLY|O_CREAT|O_TRUNC, 0644);
                dup2(fd2, 1);
                execvp(arg[0], arg);
                exit(0);
            }
            if(waitpid(pid2, status2, 0) == -1)
            {
                printf("等待子进程失败\n");
            }
            fd2 = open("text", O_RDONLY);
            dup2(fd2, 0);
            if(chazhao(arg[k+1]) == 0)
            {
                printf("%s: no input files",arg[0]);
                exit(1);
            }
            execvp (arg[k+1], arg);
            if( remove("text"))
            {
                printf("remove error\n");
            }
            exit(0);
        }
        
    }
    if(sum = cont[3] && cont[3] == 1)    //后台运行符 & ，支持如： ls&  和 ls &   和   ls  &
    {

        printf("process id = %d\n", pid);
        return;
    }

    if(waitpid(pid, status, 0) == -1)             //等待子进程结束
    {
        printf("等待子进程失败\n");
    }
}

char *rl_gets()
{
    char name[100];
    char *msg = (char *)malloc(sizeof(char)*100);
    char *str = (char *)malloc(sizeof(char)*100);
    char *usr = (char *)malloc(sizeof(char)*100);
    struct passwd* pwd = getpwuid(getuid());
    strcpy(usr, pwd->pw_name);
    gethostname(str, 100);
    getcwd(msg, 100);
    //sprintf(name,COLOR_BAGIN COLOR_BKG_SEF(41,33)"%s@%s"COLOR_END ":" COLOR_BAGIN COLOR_BKG_SEF(46,33)"%s"COLOR_END,usr,str,msg);
    sprintf(name,COLOR_BAGIN "%s@%s"COLOR_END ":" COLOR_BAGIN2 "%s$ "COLOR_END,usr,str,msg);
    if(ar)
    {
        free (ar);
        ar = (char *)NULL;
    }
    ar = readline(name);     //从shell读取字符并返回，有tab补全和光标移动
    if(ar && *ar)          
        add_history(ar);
    free(msg);
    free(str);
    free(usr);
    return ar;
}

int main()
{
    signal(SIGINT, SIG_IGN);
	char *path = (char *)malloc(sizeof(char)*100);
	getcwd(path,100);
    while(1)
    {
        char *argv[5],B[5][10];
        int i = 0,j = 0,k = 0,num,a = 0,b = 0;
        //print();                        //打印当前工作位置
        rl_gets();
        if(strcmp(ar,"exit") == 0)
        {
			//printf("%s",path);
			//chdir(path);
            exit(0);
        }
        j = strlen(ar);
        if(j <= 0)
        {
            continue;
        }
        if(j > 60)
        {
            printf("%s:no input files\n",ar);
            continue;
        }
        //printf("%d\n",j);
        for(i = 0; i < j; i++)
        {
            if(ar[i] < 0)
            {
                a++;
            }
            else
            {
                b++;
            }
        }
        num = a/3 + b;
        //printf("%d\n",num);
        for(i = 0; i < num ; i++)
        {
            j = 0;
            while(ar[i] != ' ' && i < num)
            {
                B[k][j] = ar[i];
                i++;
                j++;
            }
            B[k][j] = '\0';
            k++;
        }

        for(i = 0; i < k ; i++)
        {
            argv[i] = (char *)B[i];
        }
        argv[k] = NULL;   
        tj(argv);
        //for(i = 0; i < k; i++)
        //{
        //    printf("%s\n",argv[i]);
        //}
    }
    return 0;
}