1. 使用文件IO完成对图像的读写操作
代码
#include<myhead.h>int main(int argc, const char *argv[])
{int fd=-1;if((fd = open("./bird.bmp", O_RDWR)) == -1){perror("fopen error");return -1;}//读取该图片的大小，需要将光标向后偏移2个字节lseek(fd, 2, SEEK_SET);int bmpsize = 0;//读取出图片的大小read(fd, &bmpsize, sizeof(int));printf("bmpsize = %d\n", bmpsize);//前54字节是文件头和信息头所占空间//想要对图像内容进行读写操作//需要将光标向后偏移54字节后，再进行操作lseek(fd, 54, SEEK_SET);unsigned char color[3] = {255, 255, 255}; //定义一个颜色，白色for(int i=0; i<65; i++) //外行{for(int j=0; j<1200; j++) //内列{for (int k=0; k<3; k++){char c;read(fd, &c, sizeof(char));c=(c+32)%255;write(fd, &c, sizeof(char));}}}//关闭文件close(fd);return 0;
}
原图片
修改后图片
2. 使用stat函数实现 ls -l 指令功能
代码
#include <myhead.h>int main(int argc, const char *argv[])
{//1.define dir ptrDIR *dptr = NULL;//2.open directoryif( (dptr=opendir("./") )==NULL ){perror("opendir error ");}//3. define file ptrstruct dirent *fptr = NULL;//定义文件状态结构体struct stat st;size_t size;struct passwd *pwd=NULL;struct group *grp=NULL;//4.read files while((fptr=readdir(dptr))!=NULL){char filename[256]="./";strcat(filename, fptr->d_name);//printf("filename=%s\n", filename);//定义文件状态结构体struct stat st;//获取信息存放在结构体变量st里if( (stat(filename, &st))==-1 ){perror("stat error");return -1;}//file typeswitch (st.st_mode & S_IFMT) {case S_IFBLK: printf("b"); break;case S_IFCHR: printf("c"); break;case S_IFDIR: printf("d"); break;case S_IFIFO: printf("p"); break;case S_IFLNK: printf("l"); break;case S_IFREG: printf("-"); break;case S_IFSOCK: printf("s"); break;default: printf("unknown?\n"); break;}//file accessint au=st.st_mode&0777; //printf("au=%o\n", au);char crwx[9]="";char tmp[9]="";for(int i=0; i<3; i++){for(int j=1; j<=3; j++){char bit =(char) au&(01);if(bit==0){strcpy(tmp, "-");strcat(tmp, crwx);strcpy(crwx, tmp);}else if(bit==1 && (j%3)==1 ){strcpy(tmp, "x");strcat(tmp, crwx);strcpy(crwx, tmp);}else if(bit==1 && (j%3)==2 ){strcpy(tmp, "w");strcat(tmp, crwx);strcpy(crwx, tmp);}else if(bit==1 && (j%3)==0 ){strcpy(tmp, "r");strcat(tmp, crwx);strcpy(crwx, tmp);}au=au>>1;} }printf("%s ", crwx);printf("%ld ", st.st_nlink);pwd=getpwuid(st.st_uid);printf("%s ", pwd->pw_name);grp=getgrgid(st.st_uid);printf("%s ", grp->gr_name);printf("%10ld ", st.st_size);struct tm *at = localtime(&(st.st_atime));printf("%2d %2d %02d:%02d:%02d ", at->tm_mon+1, at->tm_mday, at->tm_hour, at->tm_min, at->tm_sec);printf("%s\n", fptr->d_name);}return 0;
}
运行结果
ubuntu@ubuntu:~/embedded/04_io/day03$ ./a.out
drwxrwxr-x 5 ubuntu ubuntu 4096 12 5 17:12:30 ..
-rwxrwxr-x 1 ubuntu ubuntu 13000 12 5 21:01:30 a.out
-rw-rw-r-- 1 ubuntu ubuntu 77 12 5 15:36:06 11_dup.c
-rwxrwxrwx 1 ubuntu ubuntu 14 12 5 14:14:42 test.txt
-rw-rw-r-- 1 ubuntu ubuntu 14 12 5 14:29:39 test.bk
-rw------- 1 ubuntu ubuntu 2844054 12 5 20:58:46 bird_r.bmp
-rw-rw-r-- 1 ubuntu ubuntu 400 12 5 11:42:12 05_umask.c
-rw-rw-r-- 1 ubuntu ubuntu 240 12 5 10:46:58 02_open.c
-rw-rw-r-- 1 ubuntu ubuntu 91 12 5 14:48:38 09_lseek.c
-rw-rw-r-- 1 ubuntu ubuntu 109 12 5 15:02:35 10_fd_cpy.c
-rw-rw-r-- 1 ubuntu ubuntu 1007 12 5 20:53:17 12_hw_read_write.c
-rw-rw-r-- 1 ubuntu ubuntu 215 12 5 09:42:22 01_file_desc.c
-rw-rw-r-- 1 ubuntu ubuntu 2139 12 5 21:00:37 14_hw_stat.c
drwxrwxr-x 2 ubuntu ubuntu 4096 12 5 21:01:30 .
-rw-rw-r-- 1 ubuntu ubuntu 910 12 5 17:20:39 13_stat.c
-rw-rw-r-- 1 ubuntu ubuntu 527 12 5 13:59:38 07_read_write.c
-rw-rw-r-- 1 ubuntu ubuntu 385 12 5 11:33:14 04_open_excl.c
-rw-rw-r-- 1 ubuntu ubuntu 734 12 5 14:32:39 08_cpy.c
-rw-rw-r-- 1 ubuntu ubuntu 594 12 5 20:47:33 06_close.c
-rw-rw-r-- 1 ubuntu ubuntu 247 12 5 11:28:57 03_open.c
)
