linux復習資料

1、1、指令格式：指令名稱 選擇項 參數(shù)列表選擇項以-開頭通配符* ：代表文件名中的任意長度的字符串；？：代表文件名中的任一字符 ：代表文件名中的任一屬于字符組中的字符2、3 gcc基本選項類型說明-E預處理后即停止，不進行編譯、匯編及連接-S編譯后即停止，不進行匯編及連接-c編譯或匯編源文件，但不進行連接-o file指定輸出文件file程序的編譯要經(jīng)歷預處理、編譯、匯編以及連接4個階段。4、其他常用工具：putty、makefile、Emacs編輯器5、Linux系統(tǒng)中“一切皆文件”。Linux操作系統(tǒng)是以文件為基礎而設計的，除了常規(guī)文件以外，目錄、設備、管道等都屬于文件。6、文件操作方式：#

2、define O_ACCMODE 0003 /主要訪問權限位的低兩位用來測試權限用#define O_RDONLY 00#define O_WRONLY 01#defein O_RDWR 02#define O_CREAT 0100#define O_EXCL 0200 /如果存在，返回錯誤#define O_NOCTTY 0400 /終端控制信息#define O_TRUNC 01000#define O_APPEND 020007、 文件打開與創(chuàng)建： if(fd_open=open("/bin/ls",O_RDONLY) = -1)perror("open&q

3、uot;);exit(EXIT_FAILURE); if(fd_open_create=open("./tmp",O_CREAT|O_EXCL,0644) = -1)perror("open");exit(EXIT_FAILURE);if(fd_create=creat("./tmp2",0644) = -1 )perror("open");exit(EXIT_FAILURE);8、 獲取文件屬性statint stat ( const char *file_name, struct stat *buf );int

4、 fstat ( int filedes, struct stat *buf );9、 opendir、closedir、readdirDIR *opendir ( const char *name );int closedir (DIR * dirp);struct dirent *readdir ( DIR * dir );10、進程及其狀態(tài)進程就是程序的一次執(zhí)行過程。進程至少要有三種基本狀態(tài)。這三種基本狀態(tài)是：運行態(tài)、就緒態(tài)和封鎖態(tài)（或等待態(tài)）。進程轉(zhuǎn)換：11、 條件：由于父子進程執(zhí)行順序的不確定性，當子進程先于父進程退出時，子進程會留下一些資源來記錄運行的信息，以提供給父進程進行訪問。

5、如果父進程沒有調(diào)用wait或waitpid函數(shù)的話，則子進程將會一直保留這些信息，成為僵尸進程。如果父進程調(diào)用了wait函數(shù)，子進程就不會成為僵尸進程。孤兒進程是指因父親進程先結束而導致一個子進程被init進程收養(yǎng)的進程。12、 可以通過以下方式結束進程。<1>、調(diào)用exit或_exit。<2>、在main函數(shù)中執(zhí)行return。<3>隱含的離開main函數(shù)。Return與exit區(qū)別：return 退出當前函數(shù)主體，exit()函數(shù)退出當前進程，因此，在main函數(shù)里面return(0)和exit(0)完成一樣的功能。return僅僅從子函數(shù)中返回，而子進

6、程用exit()退出，調(diào)用exit()時要調(diào)用一段終止處理程序，然后關閉所有I/O流。13、管道（Pipe）及有名管道（named pipe）：管道可用于具有親緣關系進程間的通信，有名管道克服了管道沒有名字的限制，因此，除具有管道所具有的功能外，它還允許無親緣關系進程間的通信；管道的實質(zhì)是一個內(nèi)核緩沖區(qū)，進程以先進先出的方式從緩沖區(qū)中存取數(shù)據(jù)：管道一端的進程順序地將數(shù)據(jù)寫入緩沖區(qū)，另一端的進程則順序地讀出數(shù)據(jù)。兩個局限性：1）支持半雙工；2）只有具有親緣關系的進程之間才能使用這種無名管道；讀寫特殊性：1.當讀一個寫端已經(jīng)關閉的管道時，在所有數(shù)據(jù)被讀取之后，read函數(shù)返回值為0，以指示到了文件

7、結束處；2.如果寫一個讀端關閉的管道，則產(chǎn)生SIGPIPE信號。如果忽略該信號或者捕捉該信號并處理程序返回，則write返回-1，errno設置為EPIPE14、 父子進程通過無名管道通信elseclose(pipe_fd0);printf("please input the string:");scanf("%s",buf_w);if(write(pipe_fd1,buf_w,strlen(buf_w)!=-1)printf("parent process has written:%s to the pipe!n",buf_w);c

8、lose(pipe_fd1);waitpid(result,NULL,0);exit(0);#include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <sys/wait.h>#include <unistd.h>#include <string.h>main()pid_t result;int r_num;int pipe_fd2;char buf_r100,buf_w100;memset(buf_r,0,sizeof(buf_r);if(pip

9、e(pipe_fd)<0)perror("pipe");exit(EXIT_FAILURE);result=fork();if(result<0)perror("fork");exit(EXIT_FAILURE);else if(result=0)close(pipe_fd1);if(r_num=read(pipe_fd0,buf_r,100)>0)printf("child process has read %d characters from the pipe,the string is:%sn",r_num,b

10、uf_r);close(pipe_fd0);exit(0);信號是Linux系統(tǒng)中用于進程之間相互通信或操作的一種機制。信號事件的發(fā)生有兩個來源：1. 硬件來源：用戶按某些終端鍵時將產(chǎn)生信號，如CTRL+C將產(chǎn)生SIGINT（中止信號）；硬件異常產(chǎn)生信號，如除數(shù)為0或無效的存儲訪問等。2. 軟件來源：終止進程信號，其他進程調(diào)用kill函數(shù)，將信號發(fā)送個另一個進程或進程組；軟件異常產(chǎn)生信號。信號處理信號注銷信號注冊內(nèi)核進程用戶進程信號產(chǎn)生*生命周期（3）設計一個程序，要求打開文件“pass”，如果沒有這個文件，新建此文件；讀取系統(tǒng)文件“/etc/passwd”，把文件中的內(nèi)容都寫入“pass”文

11、件。#include <stdio.h>#include <stdlib.h>#include <fcntl.h>#include <string.h>#include <sys/types.h>int main(int agrs,char *args) int fd_src,fd_des,num;char buf10; if(fd_des=open("pass",O_CREAT|O_WRONLY|O_TRUNC,0644)<0) perror("open or create file failed

12、n"); exit(EXIT_FAILURE);if(fd_src=open("/etc/passwd",O_RDONLY,0644)=-1) perror("open passwd file failedn");exit(EXIT_FAILURE); donum =read(fd_src,buf,10);write(fd_des,buf,num);while(num >= 10);close(fd_src); close(fd_des); return 0;（4）設計一個程序，要求新建一個目錄，預設權限為d-x-x-x。 #includ

13、e<stdio.h> #include<dirent.h> #include<sys/types.h> #include<sys/stat.h>#include <fcntl.h>#include <stdlib.h>int main(int argc,char *argv)DIR *dir;int fd; if(fd=mkdir("/home/student/dir",0644)=-1) perror("directory created failed!"); exit(EXIT_

14、FAILURE); if(chmod("dir",S_IXUSR|S_IXGRP|S_IXOTH)<0)perror("chomd");exit(EXIT_FAILURE);return 0;. 實現(xiàn)兩個進程間使用消息隊列進行通信/接受消息#include<unistd.h>#include<stdlib.h>#include<stdio.h>#include<string.h>#include<errno.h>#include<sys/msg.h>#define BUFIZE

15、 1024struct msg_stlong int msg_type;char textBUFIZE;int main()int running=1;int msgid=-1;struct msg_st data;long int msgtype=0;/創(chuàng)建消息隊列msgid=msgget(key_t)1234,0666|IPC_CREAT);if(msgid=-1)fprintf(stderr,"msgget failed with error:%dn",errno);exit(EXIT_FAILURE);/從隊列中獲取消息，直到遇到end消息為止while(runni

16、ng)if(msgrcv(msgid,(void *)&data,BUFIZE,msgtype,0)=-1)fprintf(stderr,"msgget failed with error:%dn",errno);exit(EXIT_FAILURE)；printf("You wrote %sn",data.text);/遇到end結束if(strncmp(data.text,"end",3)=0)running=0;/刪除消息隊列if(msgctl(msgid,IPC_RMID,0)=-1)fprintf(stderr,&qu

17、ot;msgctl(IPC_RMID)failedn");exit(EXIT_FAILURE);exit(EXIT_SUCCESS);return 0;/發(fā)送消息#include<unistd.h>#include<stdlib.h>#include<stdio.h>#include<sys/msg.h>#include<errno.h>#define MAX_TEXT 512#define BUFSIZE 1024struct msg_stlong int msg_type;char textMAX_TEXT;int ma

18、in()nt running=1;struct msg_st data;char bufferBUFSIZE;int msgid=BUFSIZE;/建立消息隊列msgid=msgget(key_t)1234,0666|IPC_CREAT);if(msgid=-1)fprintf(stderr,"msgget failed with error:%dn",errno);exit(EXIT_FAILURE);/向消息隊列中寫消息，直到寫入end結束while(running)/寫入數(shù)據(jù)printf("Enter some text:");fgets(buff

19、er,BUFSIZE,stdin);data.msg_type=1;strcpy(data.text,buffer);/消息隊列發(fā)送消息if(msgsnd(msgid,(void *)&data,MAX_TEXT,0)=-1)fprintf(stderr,"msgsnd failedn");exit(EXIT_FAILURE);/輸入end結束if(strncmp(buffer,"end",3)=0)running=0;sleep(1);exit(EXIT_SUCCESS);return 0; 2. 上機調(diào)試課件中killrecever和kill

20、sender程序。/killrecever#include <stdio.h>#include <unistd.h>#include <sys/types.h>#include <signal.h>/SIGUSR1信號處理函數(shù)void CbSigUsr1(int signo) /輸出接收到的信號信息printf("nreceive signal=%d.n",signo);void main()/安裝SIGUSR1信號if(signal(SIGUSR1,CbSigUsr1)=SIG_ERR)perror("signal

21、");return;printf("my pid is %dn",getpid(); printf("waiting for SIGUSR1.n");/暫停，等待信號 pause();/killsender#include <stdio.h>#include <signal.h>#include <unistd.h>#include <stdlib.h>void fun_ctrl_c();int main()(void)signal(SIGINT,fun_ctrl_c);printf("

22、Now I'm starting.n");while(1)printf("this is an endless loop unless Ctrl+c are pressd!n");sleep(2);exit(0);void fun_ctrl_c()printf("tCtrl+c were pressed!n");printf("t This is just an example for signal function!n");printf("treset signal SIGINTn");(voi

23、d)signal(SIGINT,SIG_DFL)1. 編程實現(xiàn)由一個父進程產(chǎn)生3個子進程，并且給三個子進程傳遞不同的參數(shù)，收到a的子進程在顯示器上輸出乘法口訣表；收到b的子進程計算10??；收到c的進程計算1+2+3+19+20的結果。 /計算10！#include<stdio.h> int main()int fac=1,i; for(i=1;i<=10;i+) fac*=i;if(i<10)printf("%d*",i); Else printf("%d=",i); printf("%dn",fac);ret

24、urn 0;/乘法口訣表#include <stdio.h>int main()int i,j,result=0;for(i=1;i<=9;i+)or(j=1;j<=i;j+)result=i*j;printf("%d*%d=%d ",i,j,result);printf("n");return 0;/計算1+2+3+19+20的結果#include<stdio.h> int main()int sum=0,i; for(i=1;i<=20;i+) sum+=i;if(i<20)printf("%

25、d+",i); Else printf("%d=",i); printf("%dn",sum); return 0;/主進程#include<stdio.h>#include<stdlib.h>#include<sys/types.h>#include<unistd.h>int main(int argc,char *argv ) int flag;pid_t pid;int i=1;int sum=0;int fac=1; while(i<4) pid=fork(); if(pid=-1)

26、 perror("fork");exit(EXIT_FAILURE); switch(*argvi) case 'a': if(pid=0)printf("this is 1 child processn");for(int i=1;i<=9;i+)for(int j=1;j<=i;j+)result=i*j;printf("%d*%d=%d ",i,j,result);printf("n");break;case 'b': if(pid=0) sleep(1);prin

27、tf("this is 2 child processn");for(int i=1;i<=10;i+) fac*=i;(i<10)printf("%d*",i);else printf("%d=",i);printf("%dn",fac); break; case 'c': if(pid=0) sleep(2); printf("this is 3 child processn"); for(int i=1;i<=20;i+) sum+=i; if(i<

28、20)printf("%d+",i);else printf("%d=",i); printf("%dn",sum); break;default: exit(EXIT_FAILURE); / if(i!=3) return 0; i+; return 0;2. execve函數(shù)的應用，要在程序執(zhí)行時設定環(huán)境變量，路徑為tmp，用戶為liu，執(zhí)行命令env時把這些環(huán)境變量傳遞給系統(tǒng)。在這一函數(shù)中，參數(shù)e表示可傳遞新進程環(huán)境變量，參數(shù)v表示傳遞的參數(shù)（含命令）為構造指針數(shù)組，文件查找需給出路徑。命令env在“/bin”目錄下。把環(huán)境變量

29、設定為： char *envp=“PATH=/tmp”,”USER=liu”,NULL;參數(shù)的構造指針數(shù)組為：char *arg=“env”,NULL;因而此函數(shù)的調(diào)用形式為：execve(“/bin/env”,”env”,envp);請編寫程序進行調(diào)試。 #include<stdio.h>#include<stdlib.h>#include<unistd.h>int main()char *env="env",NULL; char *envp="PATH=/tmp","USER=liu",NULL

30、; execve("/bin/env",env,envp);return 0;使用POSIX IO實現(xiàn)計算文件大小#include <stdlib.h>#include <stdio.h>#include <errno.h>#include <fcntl.h>int my_callen ( int fd ) int len; if ( lseek( fd , 0 , SEEK_END ) = -1 ) perror( "lseek“); if ( ( len = lseek ( fd , 0 , SEEK_CUR )

31、 ) = -1 ) perror( "lseek“); return len;int main ( int argc , char * argv ) int len = -1; int fd; if ( argc < 2 ) perror ( "para“) ; if ( ( fd = open ( argv1 , O_RDONLY ) ) =-1 ) perror ( "open“) ; exit(EXIT_FAILURE); len = my_callen ( fd ) ; close(fd); if(len<0) perror ( "c

32、al“) ;elseprintf ( "There are %d bytes in file %s!n“ , len , argv1 ); return 0; 列出目錄下的文件信息#include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <dirent.h>#include <errno.h>int main ( int argc, char * argv ) if ( argc < 2 ) printf ( "usage:my_g

33、etdir dirnamen“ ) ; exit ( 0 ); if ( my_read ( argv1 ) < 0 ) exit ( EXIT_FAILURE ); return 0;int my_read ( const char * path ) DIR *dir ; struct dirent *ptr; if ( ( dir = opendir ( path ) ) = NULL ) perror (" opendir“);exit(EXIT_FAILURE); while ( ( ptr = readdir ( dir ) ) != NULL ) printf (

34、"file inode :%ldtt“ , ptr->d_ino ); printf ( "file name :%sn“ , ptr->d_name ); closedir ( dir ); return 0;例：生成多個子進程#include <stdio.h>#include <stdlib.h>#include <unistd.h>main() pid_t pid; int i=1;while(i<9) pid=fork();if(pid=0) printf("I'm no. %d proces

35、s, my pid is %d.n", i, getpid();if(i!=1)return 0;i+;由于父子進程執(zhí)行順序的不確定性，當子進程先于父進程退出時，子進程會留下一些資源來記錄運行的信息，以提供給父進程進行訪問。如果父進程沒有調(diào)用wait或waitpid函數(shù)的話，則子進程將會一直保留這些信息，成為僵尸進程。如果父進程調(diào)了wait函數(shù)，子進程就不會成為僵尸進程。用孤兒進程是指因父親進程先結束而導致一個子進程被init進程收養(yǎng)的進程。signal的應用#include <stdio.h>#include <signal.h>#include <u

36、nistd.h>#include <stdlib.h>void fun_ctrl_c();int main()(void)signal(SIGINT,fun_ctrl_c);printf("Now I'm starting.n");while(1)printf("this is an endless loop unless Ctrl+c are pressd!n");sleep(2);exit(0);void fun_ctrl_c()printf("tCtrl+c were pressed!n");print

37、f("t This is just an example for signal function!n");printf("treset signal SIGINTn");(void)signal(SIGINT,SIG_DFL);創(chuàng)建消息隊列#include <stdio.h>#include <sys/ipc.h>#include <sys/types.h>int main()key_t key;key=ftok(".",1);printf("the key is %xn",ke

38、y);int id;id=msgget(key+1,IPC_CREAT|0666);printf("id=%dn",id);system(“ipcs”);刪除消息隊列#include <stdio.h>#include <sys/ipc.h>#include <sys/types.h>int main()key_t key;int id;key=ftok(".",1);id=msgget(key+1,IPC_CREAT|0666);printf("id=%dn",id);msgctl(id,IPC_

39、RMID,NULL);sytem(“ipcs”);將數(shù)組str中的數(shù)據(jù)寫入文件strtext.txt中，每行一條數(shù)據(jù)；隨后，將文件中的數(shù)據(jù)讀入到數(shù)組out中，輸出out數(shù)組的數(shù)據(jù)。#include <stdio.h>#include <stdlib.h>main() char str15="January","February","March","April","May", "June","July","August&qu

40、ot;,"september","October","November","December"char out1215;FILE *fp;int i;fp=fopen("strtext.txt","w");if(fp=NULL)printf("cant open file!n");exit(1); fwrite(str,15,12,fp); fclose(fp); printf("write data success!n");fp=fo

41、pen("strtext.txt","r"); if(fp=NULL)printf("cant open file!n"); exit(1);fread(out,15,12,fp); fclose(fp);printf("read data success!n"); printf("the data in array out are:n"); for(i=0;i<12;i+) printf("%sn",outi);fscanf函數(shù)實現(xiàn)scanf函數(shù)的功能#include

42、 <stdio.h>const int MAX_N = 21;int main()int i;char x;FILE *myfile = fopen("test.txt", "r"); if (myfile) for (i = 1; i <= MAX_N; i+) fscanf(myfile, "%c", &x)；printf("%c", x); return 0;將文件描述符轉(zhuǎn)換為流對象#include <stdio.h>#include <stdlib.h>#i

43、nclude <unistd.h>#include <fcntl.h>#include <sys/stat.h>main() int fd;FILE *stream;unlink("test.txt"); fd=open("test.txt",O_CREAT|O_WRONLY,S_IREAD|S_IWRITE)stream=fdopen(fd,"w");if(stream=NULL) printf("fdopen failedn");else fprintf(stream, &q

44、uot;Hello worldn"); fclose(stream);printf("the content of the test.txt is:n"); system("cat test.txt"); return 0; 文件的創(chuàng)建，打開#include <fcntl.h>#include <stdio.h>#include <stdlib.h>main(int argc, char * argv ) int fd_open, fd_open_create, fd_create; if(fd_open=o

45、pen("/bin/ls",O_RDONLY) = -1)perror("open");exit(EXIT_FAILURE); printf ( "the file's descriptor is: %dn " , fd_open ); if(fd_open_create=open("./tmp",O_CREAT|O_EXCL,0644) = -1)perror("open");exit(EXIT_FAILURE); printf ( " the tmp1 file descr

46、iptor is: %dn" ,fd_open_create);if(fd_create=creat("./tmp2",0644) = -1 )perror("open");exit(EXIT_FAILURE); printf("the tmp2 file descriptor is: %dn",fd_create);close(fd_open); close(fd_open_create); close(fd_create); return 0;文件讀寫#include <stdio.h>#include &l

47、t;stdlib.h>#include <unistd.h>int main() char buf80; int n; n=read(STDIN_FILENO,buf,80);if(n<0) perror("read STDIN_FILENO"); exit(EXIT_FAILURE); write(STDOUT_FILENO,buf,n); printf("n");return 0;使用POSIX IO實現(xiàn)文件拷貝 #include <stdio.h>#include <stdlib.h>#include

48、 <fcntl.h>#include <string.h>#include <sys/types.h>main(int argc, char * argv) int fd_src,fd_des; char buf128;int num;if(argc!=3) printf("tje format must be: cp file_src file_des");exit(EXIT_FAILURE); if(fd_src=open(argv1,O_RDONLY)=-1) perror("open1");exit(EXIT_

49、FAILURE); if(fd_des=open(argv2,O_CREAT|O_EXCL|O_WRONLY,0644)=-1) perror("open2");exit(EXIT_FAILURE); do num=read(fd_src,buf,128);write(fd_des,buf,num);while(num=128);close(fd_src); close(fd_des);父子進程的交替執(zhí)行int main() pid_t pid; printf(“Lets study fork function!n”); pid=fork(); switch(pid) ca

50、se -1: perror(“fork failure”); break; case 0: printf(“hellow, Im child process, my pid is %d, my parent is %d!n”, getpid(), getppid(); break;default:printf(“hi, Im parent process, my pid is %d!n”,getpid(); break; exit(0);父子進程讀寫文件#include <stdlib.h>#include <stdio.h>#include <unistd.h&

51、gt;#include <sys/stat.h>#include <sys/types.h>#include <fcntl.h>int main() int fd; pid_t pid; char buf45;if ( ( fd = open ( “code”, O_CREAT|O_RDWR|O_TRUNC, S_IRWXU ) ) < 0 ) perror ( "open error“ ); exit ( 0 ); pid = fork ( );switch ( pid ) case -1: perror ( "fork erro

52、r“ ); break; case 0: printf ( "child processn“ ); if (write(fd,"I'm child process. Daddy, do you see me?“,41 )<0) perror ( "child error“ ); exit ( 0 ); break; default : sleep ( 6 ); printf ( "nparent processn“ ); lseek ( fd, 0, SEEK_SET); if ( read ( fd, buf, 41) < 0 )

53、perror ( "parent error“ ); exit ( 0 ); printf("n%sn",buf); close(fd); break; 生成多個子進程#include <stdio.h>#include <stdlib.h>#include <unistd.h>main() pid_t pid; int i=1; while(i<9) pid=fork();if(pid=0) printf("I'm no. %d process, my pid is %d.n", i, get

54、pid(); if(i!=1)return 0;i+;產(chǎn)生一個孤兒進程#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <sys/types.h>int main ( ) pid_t pid; int k=3; pid = fork ( ); switch ( pid ) case -1: perror ( "fork errorn“ ); break;case 0 : while ( k > 0 ) printf ( "I'm ch

55、ild process, my PID is %d, my parent is %d.n", getpid ( ), getppid ( ) );sleep(1); k-;break;default : printf ( "I'm parent process, my PID is %d.n", getpid ( ) ); break; exit與return的區(qū)別C語言關鍵字與函數(shù)exit()在main函數(shù)退出時有相似之處，但兩者有本質(zhì)的區(qū)別：return 退出當前函數(shù)主體，exit()函數(shù)退出當前進程，因此，在main函數(shù)里面return(0)和exi

56、t(0)完成一樣的功能。return僅僅從子函數(shù)中返回，而子進程用exit()退出，調(diào)用exit()時要調(diào)用一段終止處理程序，然后關閉所有I/O流。守護進程的實現(xiàn) #include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <signal.h>#include <fcntl.h>#include <sys/syslog.h>#include<sys/param.h>#include<sys/types.h>#include <

57、;sys/stat.h>int init_daemon(const char *pname,int facility) int pid;int i;signal(SIGTTOU,SIG_IGN);signal(SIGTTIN,SIG_IGN);signal(SIGTSTP,SIG_IGN);signal(SIGHUP,SIG_IGN);pid=fork();if(pid>0)exit(EXIT_SUCCESS);else if(pid<0)perror("fork");exit(EXIT_FAILURE);setsid();pid=fork();if(pi

58、d>0)exit(EXIT_SUCCESS);else if(pid<0)perror("fork");exit(EXIT_FAILURE);for(i=0;i<NOFILE;i+)close(i);open("/dev/null",O_RDONLY);open("/dev/null",O_RDWR);open("/dev/null",O_RDWR);chdir("/");umask(0);signal(SIGCHLD,SIG_IGN);openlog(pname,LOG_PI

59、D,facility);return;main(int argc,char * argv) FILE *fp;time_t ticks;init_daemon(argv0,LOG_KERN);while(1)sleep(1);ticks=time(NULL);syslog(LOG_INFO,"%s",asctime(localtime(&ticks);父子進程通過無名管道通信#include <stdio.h>#include <stdlib.h>#include <sys/types.h>#include <sys/wait.h>#include <unistd.h>#include