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execute.c
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execute.c
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#include"execute.h"
#include"def.h"
#include"extern.h"
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
void execute_disk_command(void)
{
if(infile[0]!='\0')
cmd[0].infd=open(infile,O_RDONLY);
if(outfile[0]!='\0')
{
if(append)
cmd[cmd_count-1].outfd=open(outfile,O_WRONLY |O_CREAT| O_APPEND,0666);
else
cmd[cmd_count-1].outfd=open(outfile,O_WRONLY |O_CREAT| O_TRUNC,0666);
}
//因为后台作业不会调用wait,所以需要处理僵尸进程
if(backgnd==1)
signal(SIGCHLD,SIG_IGN);
else
signal(SIGCHLD,SIG_DFL);
int i;
int fds[2];
int fd;
for(i=0;i<cmd_count;++i)
{
//不是最后一条命令,创建管道
if(i<cmd_count-1)
{
pipe(fds);
cmd[i].outfd=fds[1];
cmd[i+1].infd=fds[0];
}
forkexec(i);
if((fd=cmd[i].infd)!=0)
close(fd);
if((fd=cmd[i].outfd)!=1)
close(fd);
}
if(backgnd==0&&i!=0)
{
//前台作业需要等待管道最后一个命令退出
while(wait(NULL)!=lastpid);
}
}
void forkexec(int i)
{
pid_t pid;
pid=fork();
if(pid==-1)
ERR_EXIT("fork");
if(pid>0)
{
if(backgnd==1)
printf("%d\n",pid);
lastpid=pid;
}
else if(pid==0)
{
//backgnd=1,将第一条命令的infd重定向到空文件,不用关心作业控制
if(cmd[i].infd==0&&backgnd==1)
cmd[i].infd=open("/dev/null",O_RDONLY);
//将第一个简单命令进程作为进程组组长
if(i==0)
setpgid(0,0);
if(cmd[i].infd!=0)
{
close(0);
dup(cmd[i].infd);
}
if(cmd[i].outfd!=1)
{
close(1);
dup(cmd[i].outfd);
}
int j;
for(j=3;j<1024;++j)//关闭3以上的文件描述符
close(j);
if(backgnd==0)
{
signal(SIGINT,SIG_DFL);
signal(SIGQUIT,SIG_DFL);
}
execvp(cmd[i].args[0],cmd[i].args);
exit(EXIT_FAILURE);
}
}