实验5：进程管理及操作

1、实验5进程管理及操作实验目的1. 了解进程号，进程组号，会话号。2. 清楚进程两个牛成子进程两数z间的差别实验内容a）修改程序getpgid_example.c,使结果没有父进程为1的情况。并说明原因b）有3个进程，其中一个为父进程，其余为父进程的子进程，分别打印这三个进程的 进程号，父进程号，进程组号。c）有3个进程，其中一个为父进程，其余为父进程的子进程，其中一个子进程运行“is 1“指令，另一个子进程在暂停5s后界常退出，父进程不阻塞自己，并等待子进程 的退出信息，待收到该信息，父进程返回。d）请修改提供的源码，实现简单的myshell,实验结果实验总结# in elude< st

2、dio.h># in elude< stdlib.h># in elude< unistd.h># in eludev string.h># in elude< sys/types.h># in eludev dire nt.h>#define normal 0 广一般的命令*/# define out_redirect 1 /* 输出重定向*7 #define inedirect 2 /* 输入重定向*/ #define have_pipe 3 /* 命令屮有管道*/void print_prompt();/* 打印提示符*/void g

3、etnput(char *);厂得到输入的命令*7void explain_input(char * ,int * ,char a 100 256);/* 对输入命令进行解析* /void do_cmd(int ,char a100256);/* 执行命令*/int find_command(char *);厂查找命令屮的可执行程序tint main(int argc,char * * argv)int i;int argcount = 0;char arglist100256;char * * arg = null;char * but = null;but = (char * )mallo

4、c(256);if (buf = null)perror("malloc failed");exit(-1);while(1)厂将buf所指向的空间清零*/memset(buf,0,256);print_prompt();get_input(buf);广若输入的命令为exit或logout则退出本程序* /if (strcmp(buf,"exitn") = = 0 11 strcmp(buf,"logoutn") = = 0)break;for (i= 0;i< 1 00;i+ + )arglistio = ,0,;argco

5、imt = 0;explai n_ input(buf5&argco un t,arglist); do_cmd(argco un t,arglist);广将buf所指向的内存释放* /if (but != null)free(buf);but = null;exit(o);void print_prompt()printf(”myshell$”)；厂获取用户输入*/void get_input(char * but) int len 二 0;int ch;ch = getchar();while (len <256 && ch != 'n')bu

6、flen+ + = ch;ch = getchar();if (len = = 256)printf("commond is too long n”)；exit(-1);厂输入的命令过长则退岀程序*/buflen = 叭len+ + ;buflen = ao1;广解析buf中的命令，将结果存入arglist屮，命令以回车符号n结朿*/* 如输入命令为“is -i /tmp”,则 arglist 0 , arglist 1 , arglist 2分别为 ls,l 和/t mp*/void explain_input(char * buf,int * argcount,char argl

7、ist100256) char * p = but;char * q = but;int number = 0;while(1)if (p0 = 'njbreak;if (p0 = - )p+ +;else q = p；number = 0;while (q0 != 1 ') && (q0 != 'nj) number+ +;q+ + ；/str ncpy( arg listargco unt ,p,number+ 1);arglist* argcountnumber = '0*;* argcount = * argcount + 1;p = q

8、； void do_cmd (int argcount,char arglist 100256)int flag = 0;int how = 0;厂用于指示命令屮是否含冇int background = 0;/*标识命令屮是否冇后台运彳亍标识符* /int status;int i;int fd;char *argargcount+ 1;char * argnextargcount+1 ;char * file;pid_t pid;/*将命令取出*/for (i=0;i<argcount;i+ + )argi = (char * )arglisti;argargco unt = null

9、;/*查看命令行是否有后台运行符rfor (i=0;i<argcount;i+ + )if (strncmp(argij'&”，1) = 0) if (i = argcount - 1)background = 1; argargcount-1 = null;break;else printf(hwrong commandrtj;return;for (i=0;argi != null;i+ + ) if (strcmp(argi,">") = = 0) flag+ +;how = out_redirect;if (argi+1 = null)f

10、lag+ +;if (strcmp(argi,"<") = = 0) flag+ +;how = in_ redirect;if (i = 0)flag+ +;if (strcmp(argi；t') = 0) flag+ +;how = have_pipe;if (argi+1 = null)flag+ +;if (i = 0)flag+ +;/*flag大于1,说明命令中含有多个>,v,|符号，本程序是不支持这样的命令的, 或者命令格式不对，如“is -i /tmp >h*/if (flag > 1)printf("wrong c

11、ommandn");return;if (how = outedirect) /*命令只含有一个输出重定向符号>"7for (i=0;argi != null;i+ + )if (strcmp(argi,">") = = 0)file = argi+ 1 ;argi = null;if (how = = in_redirect) /*命令只含有一个输入重定向符号v*/ for (i=0;argi != null;i+ + )if (strcmp(argi,<") = 0)file = argi+ 1;argi = null;

12、if (how = = have_pipe) /*命令只含有一个管道符号/*把管道符号后面的部分存入argnext中，管道后面的部分是一个可执行的shell命令*/for (i=0;argi != null;i+ + )if (strcmp(argi；t，) = 0)argi = null;int j;for (j=i+1；argj != null;j+ + )argnextj-i-1 =argj;argn extj-i-1 = argj;break;if (pid = fork() < 0) printf(hfork errornh); return;switch(how) case

13、0:/*pid为0说明是子进程，在子进程中执行输入的命令”/ 厂输入的命令屮不含>,v和|*/if (pid = 0)if (!(find_command(arg0)printf("%s:command not foundn",arg0);exit(o);execvp(argo,arg);exit(o);break;case 1:if (pid = 0)if (!(find_command(arg0)printf("%s: comm and not foundn",arg0);exit(o);fd = open(file,o_rdwr| o_cre

14、at| o_trunc,0644); execvp(argo,arg);exit(o);break;case 2:广输入的命令中含有重定向符v */if (pid = 0)if (!(find_command(arg0)printf("%s: comm and not foundn",arg0);exit(o);dup2(fd,0);execvp(argo,arg);exit(o);break;case 3:/ *输入的命令中含有管道* /if (pid = 0)int pid2;int status2;int fd2;if (pid2 = fork() < 0)pr

15、intf("fork2 errorn");return;else if (pid2 = = 0)if (!(find_command(arg0)printf("%s: comm and not foundnh,arg0);exit(o);fd2 = open(7tmp/youdonotknowfileh,o_wronly| o_creat| o_trunc,0644); dup2(fd2,1);execvp(argo,arg);exit(o);if (waitpid(pid2,&status2,0) = = -1)printf("wait for

16、 child process errorn");if (!(find_command(argnext0)printf("%s: comm and not foun dn",argnexto);exit(o);fd2 = open(,7tmp/youdonotknowfile,o_rdonly);dup2(fd2,0)；execvp(arg next0 ,arg next);if (remove("/tmp/youdonotknowfile")printf("remove errorn");exit(o);break;defa

17、ult:break;厂若命令屮有&,表示后台执行，父进程直接返回，不等待子进程结束*/if (background = = 1) printf("process id %dn'*,pid); return;厂父进程等待子进程结束rif (waitpid(pid,&status,o) = = -1)printf("wait for child process errorrt);int find_command(char * command)dir *dp;struct dirent * dirp;char *path =“/bin”,”/usr/bin”,null;广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(command,"./',2) = = 0) command = comma