unix环境编程练习 (1)
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函数练习
1.对mmap映射地址操作
mmap(), fstat()
mmap()： 将文件和设备空间映射到内存中，内存操作比磁盘更快。映射成功返回内存地址，是被返回-1.之后可以直接对映射的地址进行操作。
fstat()获取文件的状态。
#include <stdio.h>#include <unistd.h>#include <sys/mman.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdlib.h>#include <errno.h>int main(){ int fd=open("doc1",O_RDONLY|O_CREAT,0755); if(fd == -1){ perror("open "); exit(1); } struct stat info; fstat(fd,&info); /* start set NULL, means system set it. */ /* PROT_READ means memory can be read. */ /* MAP_PRIVATE means create a copy file, not influce origin file. */ void *start=mmap(NULL,info.st_size,PROT_READ,MAP_PRIVATE,fd,0); if(start == MAP_FAILED) { perror("mmap "); exit(1); } printf("%s",(char *)start); munmap(start,info.st_size); close(fd); return 0;}本程序将打印文件的内容。如果文件的内容为空，那么将会出现，invalid argument的错误。
2.从标准输入到标准输出
read(), write()
#include <stdio.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <unistd.h>int main(){ int n; char buf[1000]; while((n=read(STDIN_FILENO,buf,1000))>0){ //printf("output: "); if(write(STDOUT_FILENO,buf,n)!=n){ printf("write error\n"); } } if(n<0) printf("read error\n"); return 0;}/*$ ./stdin_out I sfI sfsdsdsdfsdfsdfsdf//output: output: output: */read()函数是你输入什么，它读取什么的严格类函数。（除了ctrl+D，ctrl+C等特殊情况）
3.查看标准输入的读写属性
fcntl()
使用fcnt()查看文件的属性。
#include <unistd.h>#include <stdio.h>#include <fcntl.h>int main(){ int flag=fcntl(STDIN_FILENO,F_GETFL,0); if(flag<0) { perror("error: "); return -1; } int result=flag & O_ACCMODE; if(result == O_RDONLY){ printf("stdin read only\n"); } else if(result == O_WRONLY){ puts("stdin write only"); } else if(result == O_RDWR){ puts("stdin read and write"); } else puts("stdin unknown mode"); if(flag & O_APPEND) puts("stdin append"); if(flag & O_NONBLOCK) puts("stdin nonblock"); return 0;}/*./F_GETFL stdin read and write*/4.终端交互，创建进程
fork(), fgets(), execlp()
使用fork()克隆一个新的进程。fork()有两个返回值，父进程中返回子进程的ID，子进程返回０。
for fgets():
出现换行字符、读到文件尾或是已读了size-1个字符才停止。最后会加上NULL作为字符串结束, 正常的返回值就是buf指针。
execlp()：从PATH 环境变量中查找文件并执行
因为终端输入的命令实则是一个小程序，需要进程资源，所以在这里需要fork新的进程
#include <stdio.h>#include <unistd.h>#include <stdlib.h>#include <sys/wait.h>#include <string.h>int main(){ char buf[100]; pid_t pid; int status; printf("%% "); //out put "%" while(fgets(buf,100,stdin)!=NULL){ // get cmd from stdin int len=strlen(buf); if(buf[len-1]=='\n') buf[len-1]=0; if((pid=fork())<0) puts("fork error"); //create new process else if(pid==0){ execlp(buf,buf,NULL); //execute buf cmd in new process printf("could not execute %s",buf); exit(1); } if(pid=waitpid(pid,&status,0)<0) puts("waitpid error"); printf("%%"); } return 0;}/*execute:% ls4.12.sh dex.sh doc3 for.sh t.c t%dateSat Aug 27 15:55:23 CST 2016%whoroot pts/1 2016-08-27 10:10 (10.21.1.109)root pts/0 2016-08-27 09:33 (10.21.1.109)%*/5.与文件的状态相关的写操作
fcntl()
在doc1文件中追加内容 “I love linux”
#include <stdio.h>#include <fcntl.h>#include <unistd.h>#include <string.h>int main(){ int fd=open("doc1",O_RDWR); int flag=fcntl(fd,F_GETFL,0); flag|=O_APPEND; flag=fcntl(fd,F_SETFL,&flag); // 文件的偏移量到了doc1的末尾 if(flag<0){ perror("fcntl error: "); return -1; } char buff[]="I love linux"; if(write(fd,buff,sizeof(buff))<0){ perror("write error: "); } close(fd); return 0;}6.读取文件的内容到字符串中
system(), fopen(), fgetc()
system()在使用/bin/bash如果失败则会返回127
看到fopen()可以直接使用字符串打开文件，瞬间喜欢上了它。
#include <stdio.h>#include <unistd.h>#include <fcntl.h>#include <stdlib.h>int main(){ int cmd=system("pwd > pwd_r"); if(cmd==127 || cmd==-1){ perror("system error: "); return -1; } FILE *file=fopen("pwd_r","r"); if(file==NULL) { perror("open file error: "); return -1; } char buff[1005],ch; int top=0; while((ch=fgetc(file))!=EOF){ buff[top++]=ch; } buff[top]=0; fclose(file); printf("%s",buff); return 0;}/*$ ./fopen_write /home/wei/mycode/test*/7.使用管道，父进程给子进程写一条消息“hello world.”
pipe(), fork(), read, write()
#include <unistd.h>#include <sys/types.h>#include <stdio.h>#include <string.h>int main(){ int fd[2]; // 0: read 1: write char buff[50]="hello world"; int result=pipe(fd); if(result==-1){ perror("create pipe error: "); return -1; } pid_t pid=fork(); if(pid==-1){ perror("fork error: "); return -1; } if(pid>0){ // if this is old process result=write(fd[1],buff,strlen(buff)); printf("id: %d\n",getpid()); return 0; } else { // new process read(fd[0],buff,sizeof(buff)); printf("id: %d string: %s\n",getpid(),buff); } return 0;}/*$ ./pipeid: 26517id: 26518 string: hello world*/8.阻塞的管道
fork()
观察下面的程序：
#include <unistd.h>#include <stdio.h>#include <string.h>int main(){ char buff[]="this message is sent by child process."; int fd[2]; int result=pipe(fd); if(result<0) { perror("pipe error: "); return -1; } pid_t pid=fork(); if(pid<0){ perror("create process error: "); return -1; } else if(pid==0){ close(fd[0]); int len=strlen(buff); while(len>0){ int rd=write(fd[1],buff,len); len-=rd; if(rd<0){ perror("write error: "); return -1; } else { printf("has wrote data: %d left data: %d\n",rd,len); } sleep(3); if(len==0) { printf("write finished.\n"); } } } else { close(fd[1]); char readbuff[105]; while(1){ int get=read(fd[0],readbuff,105); if(get<0){ perror("read : "); return -1; } else if(get==0) { printf("here is no contents.\n"); break; } else { printf("data : %s\n",readbuff); } } } return 0;}/*$ ./wait_pipe has wrote data: 38 left data: 0 #子进程写入数据data : this message is sent by child process. #父进程读入数据write finished. #回到了子进程here is no contents. #这是父进程//如果我们没有sleep(3)has wrote data: 38 left data: 0 #子进程write finished. #子进程data : this message is sent by child process. #父进程here is no contents. #父进程*/9.消息队列send and recv message.
ftok(), msgget(), fgets()
key_t ftok( const char * fname, int id )
fname是指定的文件名（已经存在的文件名），一般使用当前目录，如：
key_t key = ftok(“.”, 1); id是子序号。只使用8bits(1-255）。
用于保证两个不同用户下的两组相同程序获得互不干扰的IPC键值。
msgget()用于chungking或者打开消息队列。
//send.c:#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <sys/msg.h>#include <sys/types.h>#include <sys/ipc.h>#define Max 105typedef struct msgmbuf{ int msg_type; char msg_text[Max];}MsgBuf;int main(){ printf("send process start: %d\n",getpid()); printf("enter your message to send, and \"end\" will kill both process.\n"); char buff[Max]; MsgBuf sendmsg; char *msgpath="./me"; // the path of create message key_t key=ftok(msgpath,'a'); if(key==-1) { perror("create key error: "); return -1; } int msgid=msgget(key,IPC_CREAT|0777); if(msgid==-1){ perror("msgget error: "); return -1; } while(1){ printf("please enter msg: "); fgets(buff,Max,stdin); //file enter contents sendmsg.msg_type=1; strcpy(sendmsg.msg_text,buff); if(msgsnd(msgid,(void *)&sendmsg,Max,0)){ perror("msgsnd error: "); return -1; } if(strcmp(buff,"end\n")==0){ printf("send process end.\n"); return 0; } } return 0;}//recv.c:#include <stdlib.h>#include <stdio.h>#include <unistd.h>#include <string.h>#include <sys/ipc.h>#include <sys/types.h>#include <sys/msg.h>#define Max 105typedef struct msgmbuf{ int msg_type; char msg_text[Max];}MsgBuf;int main(){ printf("recv process start: %d\n",getpid()); char buff[Max]; char *msgpath="./me"; key_t key=ftok(msgpath,'a'); int msgid=msgget(key,IPC_CREAT|0777); if(msgid==-1){ perror("msgget error: "); return -1; } MsgBuf recmsg; while(1){ if(msgrcv(msgid,(void *)&recmsg,Max,0,0)==-1){ perror("msgrcv error: "); return -1; } if(strcmp(recmsg.msg_text,"end\n")==0){ printf("recv process end.\n"); break; } printf("recv msg: %s",recmsg.msg_text); } return 0;}/*$ ./sendsend process start: 20436enter your message to send, and "end" will kill both process.please enter msg: heheplease enter msg: I love youplease enter msg: endsend process end../recvrecv process start: 20437recv msg: heherecv msg: I love yourecv process end.*/10.不同进程利用共享内存通信
shmget(), shmctl()
// myshm.h #include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <sys/shm.h>#include <sys/ipc.h>#include <string.h>#define Size 105// shm.c#include "myshm.h"int main(){ key_t key=ftok("./doc",'a'); int shmid=shmget(key,Size,IPC_CREAT|IPC_EXCL|0777); if(shmid==-1){ puts("shmared memory exit. here is client."); if((shmid=shmget(key,Size,0))==-1){ //the third number is 0 means we can get the exit memory id. perror("shmget error: "); return -1; } } else puts("created new shared memory"); char buff[105], *content=NULL; printf("If you enter \"read\", we can get contents, or \"enter\", you can input new things into shared memory.\Other words will kill process. \n"); while(1){ printf("%% "); if(fgets(buff,Size,stdin)<0){ perror("fgets error: "); return -1; } content=(char *)shmat(shmid,0,0); if(content == (char *)-1){ perror("shmat: "); return -1; } if(strncmp(buff,"read",4)==0){ printf("data: \n%s",content); } else if(strncmp(buff,"enter",5)==0){ fgets(buff,Size,stdin); strcat(content,buff); printf("wrote it."); } else { /*IPC_RMID 命令实际上不从内核删除一个段，而是仅仅把这个段标记为删除，\ * 实际的删除发生在最后一个进程离开这个共享段时。*/ shmctl(shmid,IPC_RMID,0); printf("the process end, By.\n"); break; } } return 0;}/*./shmcreated new shared memoryIf you enter "read", we can get contents, or "enter", you can input new things into shared memory.Other words will kill process. % enterI love youwrote it.% readdata: I love you% enter hello world wrote it.% sthe process end, By../shmshmared memory exit. here is client.If you enter "read", we can get contents, or "enter", you can input new things into shared memory.Other words will kill process. % readdata: I love you% readdata: I love youhello world% sthe process end, By.*/11.自定义中断信号SIGINT的处理函数
signal()
#include <stdio.h>#include <stdlib.h>#include <signal.h>void stop(int sig){ printf("ctrl + c stops it!\n"); exit(0);}int main(){ signal(SIGINT,stop); while(1){ puts("hello world"); } return 0;}/*./signalhello worldhello worldhello worldhello worldhello worldhello world^Chello worldctrl + c stops it!*/12.线程创建与等待
pthread_create(), pthread_join(), pthread_self()
#include <stdio.h>#include <pthread.h>#include <unistd.h>void *thread_show(void *args){ int *thread_arg=(int *)args; printf("I'm thread %lu, counter is %d\n",pthread_self(),*thread_arg); // g(long int)syscall(178),gettid() means syscall(178) sleep(1);}int main(){ int i,ret; pthread_t thread[6]; for(i=0;i<6;i++){ printf("here is thread: %d\n",i); ret=pthread_create(&thread[i],NULL,thread_show,&i); // 第三个参数是线程的运行函数，第四个参数是运行函数的参数 if(ret!=0) printf("error: %d thread can't be created.\n",i); } for(i=0;i<6;i++){ //等待着线程结束，此时的i等于0 pthread_join(thread[i],NULL); } return 0;}/*./pthread here is thread: 0here is thread: 1here is thread: 2I'm thread 140437552871168, counter is 2I'm thread 140437544478464, counter is 2here is thread: 3here is thread: 4here is thread: 5I'm thread 140437527693056, counter is 4I'm thread 140437519300352, counter is 5I'm thread 140437536085760, counter is 3I'm thread 140437510907648, counter is 0*/ 0 0
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