Linux子程序繼承父程序的檔案描述符

#include #include #include #include #include #include #include int main()
;	pid_t pid;
int ret=0;
int fd = open("./temp.txt", o_creat|o_trunc|o_rdwr, 0666);
if( fd == -1 )
if ((pid = fork()) < 0)  
else if (pid == 0) 
else 	
waitpid(pid, null, 0);
return 0;
}

執行結果如下：

[root@lghvm001 multi_process]# gcc inherit_fd.c

[root@lghvm001 multi_process]# ./a.out

[root@lghvm001 multi_process]# cat temp.txt

parent process pid:18028, child pid:18029

child process pid:18029,parent pid:18028

結論：子程序繼承了父程序已經開啟了的檔案描述符。

寫乙個簡單的tcp server回射程式，即客戶端給伺服器端發一段字串，伺服器端將字串原樣返回。這裡伺服器端的server程式採用主程序+工作程序的模式：主程序負責接收客戶端的連線請求，然後fork乙個子程序（也叫工作程序）來處理客戶端的請求資料，即子程序接收客戶端發來的字串，然後將字串原樣返回給客戶端。這裡主要演示子程序繼承父程序的tcp socket，下面來看**：

tcp_server.c

/* tcp_server.c */  
#include #include #include #include #include #include #include #include #include #include #include #define maxline 1024  
#define backlog 50  
int main(int argc, char** argv)  
memset(&servaddr, 0, sizeof(servaddr));      
servaddr.sin_family = af_inet;          		//ipv4  
servaddr.sin_addr.s_addr = htonl(inaddr_any);   //自動填入本機的ip位址    
/*if( inet_pton(af_inet, "172.23.1.180", &servaddr.sin_addr) <= 0)
*/servaddr.sin_port = htons(6666);        //將埠號轉換為網路位元組序  
if( bind(listenfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) == -1)  
if( listen(listenfd, backlog) == -1)  
printf("*****=waiting for client's connect requestion*****=\n");   
while(1) 
if ((pid = fork()) < 0)  
else if (pid == 0)       
buff[n] = '\0';      
fputs("recv msg from client: ", stdout);  
fputs(buff, stdout);  
while (n > 0)    
if((n = recv(connfd, buff, maxline-1, 0)) < 0)       
buff[n] = '\0';      
fputs(buff, stdout);  
}  close(connfd);
exit(0);
}		else      
}  return 0;
}

客戶端**tcp_client.c

/* tcp_client.c */  
#include#include#include#include#include#include#include#define maxline 1024  
int main(int argc, char** argv)  
*/      
memset(recvline, 0, maxline);  
memset(sendline, 0, maxline);  
if( (sockfd = socket(af_inet, sock_stream, 0)) < 0)      
memset(&servaddr, 0, sizeof(servaddr));      
servaddr.sin_family = af_inet;      
servaddr.sin_port = htons(6666);   
servaddr.sin_addr.s_addr = htonl(inaddr_any);
/*    if( inet_pton(af_inet, argv[1], &servaddr.sin_addr) <= 0)*/      
if( connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)      
printf("send msg to server: \n"); 
while(1)   
fputs("echo from server:\n", stdout);  
received = 0;  
while(received < len)   
else if(bytes == 0)   
received += bytes;  
recvline[bytes] = '\0';  
fputs(recvline, stdout);  
}  fputs("\n", stdout);   
}     
close(sockfd);      
return 0; 
}

開啟linux的命令列終端，編譯執行tcp_server

另外再開啟兩個命令列終端，編譯執行tcp_client

執行結果如下：

tcp_server

[root@lghvm001 multi_process]# gcc tcp_server.c -o tcp_server [root@lghvm001 multi_process]# ./tcp_server *****=waiting for client's connect requestion*****= connected, client addr: 255.127.0.0 recv msg from client: hi,this is client1. connected, client addr: 127.0.0.1

recv msg from client: hi, this is client2.

tcp_client1

[root@lghvm001 multi_process]# gcc tcp_client.c -o tcp_client [root@lghvm001 multi_process]# ./tcp_client send msg to server: hi,this is client1. echo from server:

hi,this is client1.

tcp_client2

[lgh@lghvm001 multi_process]$ ./tcp_client send msg to server: hi, this is client2. echo from server:

hi, this is client2.

該示例有多少個客戶端連線就會產生多少個子程序，目前有主程序，兩個子程序：

[lgh@lghvm001 desktop]$ ps -ef | grep tcp_server root 18302 43605 0 14:08 pts/14 00:00:00 ./tcp_server root 18309 18302 0 14:09 pts/14 00:00:00 ./tcp_server root 18311 18302 0 14:09 pts/14 00:00:00 ./tcp_server lgh 18313 18132 0 14:09 pts/22 00:00:00 grep tcp_server

[lgh@lghvm001 desktop]$

若客戶端連線太多，會導致多過的子程序，可以使用多路io復用進行優化，在linux下epoll是不二選擇。

Linux子程序繼承父程序的檔案描述符

子程序繼承父程序中互斥鎖的討論

Linux中建立新的程序，父程序等待子程序的退出

fork 子程序不繼承父程序開啟的檔案描述符

Linux子程序繼承父程序的檔案描述符

子程序繼承父程序中互斥鎖的討論

Linux中建立新的程序，父程序等待子程序的退出

fork 子程序不繼承父程序開啟的檔案描述符

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