my_shell.c

来源：互联网发布：软件激活码拿码平台编辑：程序博客网时间：2024/05/29 07:12
#include<stdio.h>#include<string.h>#include<pwd.h>#include<stdlib.h>#include<sys/types.h>#include<unistd.h>#include<sys/wait.h>#include<fcntl.h>#include<dirent.h>#include<readline/readline.h>#include<readline/history.h>#include<signal.h>#define PIPE 1#define IN 2#define OUT 4#define OUTAPP 16int get_param(char *,char (*str)[256]);void explain_param(char (*str)[256],int *param,int k);//解释参数int getlenth(int start,char *buf);//获取字符串长度int getstart(int end,char *buf);//获得非空字符串的开始int empty(char *str){    for (int i = 0; i < strlen(str); i++) {        if (str[i] != ' ')            return 0;    }    return 1;}int main(){    char *buf;    char str[100][256]={0};    int pid;    int param=0;    int k;//二维数组的一维大小    chdir("/home/cwh");    //阻断SIGINT SIGQUIT SIGSTOP SIGTSTP    signal(SIGINT, SIG_IGN);//屏蔽ctrl+c或+z    signal(SIGQUIT, SIG_IGN);    signal(SIGSTOP, SIG_IGN);    signal(SIGTSTP, SIG_IGN);    while(1)    {        param=0;        char tip[500];        struct passwd *pwd;        memset(str, 0, sizeof(str));        pwd=getpwuid(getuid());        sprintf(tip,"%s:%s$ ",pwd->pw_name,get_current_dir_name());        buf=readline(tip);        if(strcmp(buf,"exit")==0)//输入exit退出            break;        int isempty = empty(buf);        if (isempty)            continue;        add_history(buf);//记录历史记录，实现上下左右查看        k=get_param(buf,str);        explain_param(str,&param,k);    }    exit(0);}int getstart(int start,char * buf)//得到非空格下标{    while(buf[start]==' ' && start<=strlen(buf))        start++;    return start;}int getlenth(int start,char *buf)//获得非空字符串长度{    int lenth=0;    for(int i=start+1;i<strlen(buf);i++)    {        if(buf[i]!=' ')            lenth++;        else            break;    }    return lenth;}int get_param(char *buf,char (*str)[256]){    int start=0,end=0,k=0;//方法一，判断函数起点和终点的空格问题    int flag;    while(end<strlen(buf))    {        start=getstart(start,buf);        int lenth=getlenth(start,buf);        end=start+lenth+1;        strncpy(str[k++],buf+start,lenth+1);//用strncpy可以实现从指定起始位置开始复制        if(strcmp(str[k-1],"")==0)            k--;        start=end;    }    return k;}    /*    char st[5000];//方法二    strcpy(st, buf);    char bf[5000], gf[5000];    int i = 0;    while (sscanf(st,"%s %[^\n]", bf, gf) == 2)//就是将输入分为两部分v    {        strcpy(str[i++], bf);        strcpy(st, gf);    }    strcpy(str[i++], st);    for (int j = strlen(str[i - 1]) - 1; j >= 0; j--)    {        if (str[i - 1][j] == ' ')            str[i - 1][j] = '\0';        else            break;    }    return k;    */void explain_param(char (*str)[256],int *param,int k){    int i;    char store[100][256]={0};//存ls参数    char rest[256];    int back=0;    int len=k;    int flag=0;    int m=0;    int file=0;    char file2[100][256]={0};    for(i=0;i<len;i++)    {        if(strcmp(str[i],"cd")==0)        {            flag=1;            continue;        }        if(strcmp(str[i],">")==0)//一定要++i，不然就会重复读取        {            (*param)|=OUT;            strcpy(rest,str[++i]);            continue;        }        if(strcmp(str[i],">>")==0)        {            (*param)|=OUTAPP;            strcpy(rest,str[++i]);            continue;        }        if(strcmp(str[i],"<")==0)        {            (*param)|=IN;            strcpy(rest,str[++i]);            continue;        }        if(strcmp(str[i],"|")==0)        {            (*param)|=PIPE;            for(int j=i+1;j<len;j++)                strcpy(file2[file++],str[j]);            break;        }        if(strcmp(str[i],"&")==0)        {            back=1;            continue;        }        strcpy(store[m++],str[i]);    }    char *argv[256];    char *pipe[256];    if((*param)&PIPE)//记录管道符号的后半部分    {        for(i=0;i<file;i++)            pipe[i]=file2[i];        pipe[i]=(char*)NULL;    }    for(i=0;i<m;i++)    {        argv[i]=store[i];//指针数组就可以存char *NULL    }    argv[i]=(char*)NULL;    if(len==0)//只是回车或者其他字符，直接返回    {        return;    }    pid_t pid;    if(flag==0||back)        pid=fork();    if(back&&pid>0)//有了&而且父进程要结束    {        printf("process id %d\n",pid);        return ;    }        if(flag)//如果有cd的情况        {            if(len!=1)            {                if(chdir(store[0])<0)                    printf("No such file or directory\n");            }            else                chdir("/home/cwh");//单个cd可以直接切换到主目录            return ;        }    if(pid==0)    {        int is_redirect=0;        int fd;        if((*param)&OUT)            fd=open(rest,O_RDWR|O_CREAT|O_TRUNC,0644), is_redirect=1;        else if((*param)&OUTAPP)            fd=open(rest,O_RDWR|O_CREAT|O_APPEND,0644),is_redirect=1;        else if((*param)&IN)            fd=open(rest,O_RDONLY),is_redirect=2;        if((*param)&PIPE)        {            fd=open("/tmp/cwhshelltxt",O_RDWR|O_CREAT|O_TRUNC,0644);            dup2(fd,1);            execvp(store[0],argv);            exit(0);        }        if(is_redirect && fd<0)        {            perror("open");            exit(-1);        }        if(is_redirect==1)            dup2(fd, STDOUT_FILENO);        if(is_redirect==2)            dup2(fd,STDIN_FILENO);        int err=execvp(store[0], argv);        if (err!=0)            perror("#error#");        exit(0);    }    if(pid == -1)    {        printf("creat process failed!");        return;    }    if(pid > 0)    {        waitpid(pid,NULL,0);        if((*param&PIPE))        {            pid_t pid ;            pid=fork();            if(pid==0)            {                int fd;                fd=open("/tmp/cwhshelltxt",O_RDONLY);                dup2(fd,0);                execvp(pipe[0],pipe);                exit(0);            }            if(pid==-1)            {                perror("fork");                return;            }            if(pid>0)            {                waitpid(pid,NULL,0);                remove("/tmp/cwhshelltxt");                return ;            }        }        return;    }}
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