文件及目录管理 POSIX C

1、打印打开文件的描述符

code:

#include<stdio.h> #include<unistd.h> #include<stdlib.h> #include<fcntl.h> #include<sys/types.h> #include<sys/stat.h> int main(int argc,char * argv[]) { int fp1,fp2; printf("no is/t%d/n",fileno(stdin)); printf("no is/t%d/n",fileno(stdout)); printf("no is/t%d/n",fileno(stderr)); if((fp1=open("doc1",O_WRONLY))==-1) { perror("open"); exit(EXIT_FAILURE); } if((fp2=open("doc2",O_WRONLY))==-1) { perror("open"); exit(EXIT_FAILURE); } printf("%d/n",fp1); printf("%d/n",fp2); close(fp1); close(fp2); return 0; }

结果：

no is    0
no is    1
no is    2
3
4

 

2、使用 fdopen

首先使用open返回一个文件描述符，然后调用fdopen为其添加一个流对象

然后 fprintf，打印

code：

#include<sys/stat.h> #include<stdio.h> #include<fcntl.h> #include<unistd.h> #include<stdlib.h> int main(void) { int fd; FILE * stream; fd=open("doc1",O_CREAT|O_WRONLY,S_IREAD|S_IWRITE); stream=fdopen(fd,"w"); if(stream==NULL){ puts("dfopen failed"); } else{ fprintf(stream,"love the world/n"); fclose(stream); } close(fd); printf("the context is:/n"); system("cat doc1"); return 0; }

 

3、使用POSIX IO 实现文件拷贝

code：

#include<stdio.h> #include<string.h> #include<stdlib.h> #include<fcntl.h> #include<sys/types.h> int main(int argc,int * argv[]) { int fd_src,fd_des; char buf[128]; int num; if((fd_src=open(argv[1],"O_RONLY"))==-1){ perror("open"); exit(EXIT_FAILURE); } if((fd_des=open(argv[2],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); return 0; }

运行：./run3 doc1 doc3

 

4、利用lseek函数，实现文件定问，把内容写到指定的地方

#include<stdio.h> #include<sys/types.h> #include<sys/stat.h> #include<fcntl.h> #include<stdlib.h> char buf1[]="0123456789"; char buf2[]="ABCDEFGHIJ"; char buf3[]="abcdefghij"; int main() { int fd; if((fd=creat("doc4",0644))<0){ perror("create"); exit(EXIT_FAILURE); } if(write(fd,buf1,10)!=10){ perror("write"); exit(EXIT_FAILURE); } if(lseek(fd,20,SEEK_SET)==-1){ perror("lseek"); exit(EXIT_FAILURE); } if(write(fd,buf2,10)!=10){ perror("write"); exit(EXIT_FAILURE); } if(lseek(fd,10,SEEK_SET)==-1){ perror("lseek"); exit(EXIT_FAILURE); } if(write(fd,buf3,10)!=10){ perror("write"); exit(EXIT_FAILURE); } return 0; }

结果：0123456789abcdefghijABCDEFGHIJ

 

5、列出某目录下 非隐藏文件基本信息

code：

#include<stdio.h> #include<stdlib.h> #include<dirent.h> int main(int argc,char * argv[]){ DIR* dirp; struct dirent * dp; dirp=opendir(argv[1]); while((dp=readdir(dirp))!=NULL){ if(dp->d_name[0]=='.') continue; printf("inode is %d/t",dp->d_ino); printf("reclen is %d/t",dp->d_reclen); printf("name is %s/n",dp->d_name); } closedir(dirp); return 0; }

结果：

inode is 1045265    reclen is 24    name is run2
inode is 1045138    reclen is 24    name is run4
inode is 1044932    reclen is 24    name is doc3
inode is 1045114    reclen is 24    name is doc1
inode is 1045109    reclen is 32    name is test3.c~
inode is 1045203    reclen is 32    name is doc1~
inode is 1045111    reclen is 32    name is test3.c
inode is 1045143    reclen is 32    name is test5.c
inode is 1045149    reclen is 24    name is run5
inode is 1045181    reclen is 32    name is test1.c~
inode is 1045184    reclen is 32    name is test1.c
inode is 1045202    reclen is 32    name is test2.c~
inode is 1044933    reclen is 32    name is test2.c
inode is 1045183    reclen is 24    name is doc2
inode is 1045187    reclen is 24    name is run
inode is 1045130    reclen is 24    name is doc4
inode is 1045132    reclen is 32    name is test4.c
inode is 1045135    reclen is 32    name is test5.c~
inode is 1045118    reclen is 24    name is run3

 

6、操作工作路径：

code：

#include<dirent.h> #include<stdio.h> #include<stdlib.h> int main(int argc,char * argv[]) { char * p; p=getcwd(NULL,128); printf("current path is %s/n",p); free(p); chdir("/home"); printf("new path is:%s/n",get_current_dir_name()); return 0; }

结果：
root@ubuntu:/code/chap5# ./run6
current path is /code/chap5
new path is:/home