1. 文件里面存放了5行数据，使用追加模式打开文件，打印前3行，并写入一行，期间使用ftell打印当前位置。

#include<func.h>
int main(int argc, char * argv[]){ARGS_CHECK(argc,2);FILE *fp= fopen("./file1","a+");fseek(fp,0,SEEK_SET);char line[100];for(int i =0 ;i<3;i++){if(fgets(line,sizeof(line),fp)!=NULL){printf("%s",line);}}printf("Current position :%ld\n",ftell(fp));fprintf(fp,"This is a new line\n");fclose(fp);return 0;
}

fprintf(fp, "This is a new line\n"); 这行代码在最后打印一句话的原因是因为你使用了追加模式打开文件。追加模式会将文件指针定位到文件末尾，所以在你使用 fseek(fp, 0, SEEK_SET); 将文件指针移动到文件开头后，接下来的写操作会将数据追加到文件末尾。因此，即使你已经将文件指针移动到了文件开头，写入的数据仍然会被追加到文件末尾，这就是为什么在结尾处打印一句话的原因。

2. 修改文件的权限，注意必须使用命令行参数。

• #include<func.h>
  int main(int argc,char**argv){ARGS_CHECK(argc,3);   //chmod 有三个变量main   0777    文件mode_t mode;sscanf(argv[1],"%o",&mode);int ret = chmod(argv[2],mode);printf("mode  = %o\n",mode);ERROR_CHECK(ret,NULL,"chmod");return 0;
  }
  

3. 使用两种方法打印当前目录。

#include<func.h>
int main(int argc,char**argv){char *ret = getcwd(NULL,0);ERROR_CHECK(ret,NULL,"getcwd");printf("%s\n",ret);return 0;
}

#include<func.h>
int main(int argc,char**argv){char buf[1024]={0};char *ret = getcwd(0,sizeof(buf));ERROR_CHECK(ret,NULL,"getcwd");printf("%s\n",buf);printf("%s\n",ret);return 0;
}

4. 传递一个路径名，还有一个文件名，搜索对应路径下是否有该文件，有就打印显示该文件的绝对路径。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sys/stat.h>
#include <dirent.h>// 搜索指定路径下是否存在指定文件，并打印该文件的绝对路径
void search_file(const char *dir_path, const char *file_name) {DIR *dir = opendir(dir_path);if (dir == NULL) {perror("opendir");return;}struct dirent *entry;struct stat statbuf;char full_path[PATH_MAX];while ((entry = readdir(dir)) != NULL) {snprintf(full_path, PATH_MAX, "%s/%s", dir_path, entry->d_name);if (stat(full_path, &statbuf) == -1) {perror("stat");continue;}if (S_ISREG(statbuf.st_mode) && strcmp(entry->d_name, file_name) == 0) {char real_path[PATH_MAX];if (realpath(full_path, real_path) == NULL) {perror("realpath");closedir(dir);return;}printf("Found file %s at path: %s\n", file_name, real_path);closedir(dir);return;}}printf("File %s not found in directory %s\n", file_name, dir_path);closedir(dir);
}int main(int argc, char *argv[]) {if (argc != 3) {fprintf(stderr, "Usage: %s <directory> <file_name>\n", argv[0]);return 1;}search_file(argv[1], argv[2]);return 0;
}

5. 传递任意一个目录路径，能够显示该目录的ls -l的效果。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <dirent.h>
#include <sys/stat.h>
#include <pwd.h>
#include <grp.h>
#include <time.h>// 显示目录的 ls -l 效果
void display_ls_l(const char *dir_path) {DIR *dir = opendir(dir_path);if (dir == NULL) {perror("opendir");return;}struct dirent *entry;struct stat statbuf;while ((entry = readdir(dir)) != NULL) {char full_path[PATH_MAX];snprintf(full_path, PATH_MAX, "%s/%s", dir_path, entry->d_name);if (stat(full_path, &statbuf) == -1) {perror("stat");continue;}// 打印文件类型和权限printf((S_ISDIR(statbuf.st_mode)) ? "d" : "-");printf((statbuf.st_mode & S_IRUSR) ? "r" : "-");printf((statbuf.st_mode & S_IWUSR) ? "w" : "-");printf((statbuf.st_mode & S_IXUSR) ? "x" : "-");printf((statbuf.st_mode & S_IRGRP) ? "r" : "-");printf((statbuf.st_mode & S_IWGRP) ? "w" : "-");printf((statbuf.st_mode & S_IXGRP) ? "x" : "-");printf((statbuf.st_mode & S_IROTH) ? "r" : "-");printf((statbuf.st_mode & S_IWOTH) ? "w" : "-");printf((statbuf.st_mode & S_IXOTH) ? "x" : "-");// 打印硬链接数、所有者、所属组、文件大小、最后修改时间和文件名struct passwd *pw = getpwuid(statbuf.st_uid);struct group *gr = getgrgid(statbuf.st_gid);printf(" %2ld %s %s %8ld %s %s\n",(long)statbuf.st_nlink, pw->pw_name, gr->gr_name,(long)statbuf.st_size, ctime(&statbuf.st_mtime), entry->d_name);}closedir(dir);
}int main(int argc, char *argv[]) {if (argc != 2) {fprintf(stderr, "Usage: %s <directory>\n", argv[0]);return 1;}display_ls_l(argv[1]);return 0;
}

6. 打印当前目录，然后改变当前目录，再打印当前目录。

#include <stdio.h>
#include <unistd.h>int main() {char cwd[1024];// 获取当前工作目录并打印if (getcwd(cwd, sizeof(cwd)) != NULL) {printf("Current working directory: %s\n", cwd);} else {perror("getcwd");return 1;}// 改变当前工作目录到 /tmpif (chdir("/tmp") != 0) {perror("chdir");return 1;}// 获取新的当前工作目录并打印if (getcwd(cwd, sizeof(cwd)) != NULL) {printf("New working directory: %s\n", cwd);} else {perror("getcwd");return 1;}return 0;
}//还是那个问题改变的不是文件的位置，而是执行程序的位置

7. 创建一个目录，然后删除掉它。

#include <stdio.h>
#include <unistd.h>int main() {const char *dir_name = "test_dir";// 创建目录if (mkdir(dir_name, 0777) == -1) {perror("mkdir");return 1;}printf("Directory created: %s\n", dir_name);// 删除目录if (rmdir(dir_name) == -1) {perror("rmdir");return 1;}printf("Directory deleted: %s\n", dir_name);return 0;
}

8. 实现tree命令的效果。

// 这里写a的代码
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <dirent.h>
#include <sys/stat.h>void print_tree(const char *path, int level) {DIR *dir = opendir(path);if (dir == NULL) {perror("opendir");return;}struct dirent *entry;while ((entry = readdir(dir)) != NULL) {if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0) {continue;}struct stat statbuf;char full_path[PATH_MAX];snprintf(full_path, PATH_MAX, "%s/%s", path, entry->d_name);if (stat(full_path, &statbuf) == -1) {perror("stat");continue;}for (int i = 0; i < level - 1; i++) {printf("|   ");}if (level > 0) {printf("|-- ");}printf("%s\n", entry->d_name);if (S_ISDIR(statbuf.st_mode)) {print_tree(full_path, level + 1);}}closedir(dir);
}int main(int argc, char *argv[]) {if (argc != 2) {fprintf(stderr, "Usage: %s <directory>\n", argv[0]);return 1;}print_tree(argv[1], 0);return 0;
}

9. 实现cp -r命令的效果。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <dirent.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>#define BUF_SIZE 1024void copy_file(const char *src_path, const char *dst_path) {int src_fd = open(src_path, O_RDONLY);if (src_fd == -1) {perror("open");return;}int dst_fd = open(dst_path, O_WRONLY | O_CREAT | O_TRUNC, 0666);if (dst_fd == -1) {perror("open");close(src_fd);return;}char buf[BUF_SIZE];ssize_t bytes_read, bytes_written;while ((bytes_read = read(src_fd, buf, BUF_SIZE)) > 0) {bytes_written = write(dst_fd, buf, bytes_read);if (bytes_written != bytes_read) {perror("write");close(src_fd);close(dst_fd);return;}}if (bytes_read == -1) {perror("read");}close(src_fd);close(dst_fd);
}void copy_dir(const char *src_path, const char *dst_path) {DIR *dir = opendir(src_path);if (dir == NULL) {perror("opendir");return;}if (mkdir(dst_path, 0777) == -1) {perror("mkdir");return;}struct dirent *entry;struct stat statbuf;while ((entry = readdir(dir)) != NULL) {if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0) {continue;}char src_child_path[PATH_MAX];char dst_child_path[PATH_MAX];snprintf(src_child_path, PATH_MAX, "%s/%s", src_path, entry->d_name);snprintf(dst_child_path, PATH_MAX, "%s/%s", dst_path, entry->d_name);if (stat(src_child_path, &statbuf) == -1) {perror("stat");continue;}if (S_ISDIR(statbuf.st_mode)) {copy_dir(src_child_path, dst_child_path);} else {copy_file(src_child_path, dst_child_path);}}closedir(dir);
}int main(int argc, char *argv[]) {if (argc != 3) {fprintf(stderr, "Usage: %s <source> <destination>\n", argv[0]);return 1;}copy_dir(argv[1], argv[2]);return 0;
}

10.新建一个文件，里边内容为hello，通过mmap映射该文件后，修改hello为world，然后解除映射

#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>int main() {const char *file_path = "test.txt";const char *data = "hello";const char *new_data = "world";// 创建并写入文件int fd = open(file_path, O_RDWR | O_CREAT, 0666);if (fd == -1) {perror("open");return 1;}write(fd, data, strlen(data));close(fd);// 映射文件到内存fd = open(file_path, O_RDWR);if (fd == -1) {perror("open");return 1;}struct stat sb;if (fstat(fd, &sb) == -1) {perror("fstat");close(fd);return 1;}char *addr = mmap(NULL, sb.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);if (addr == MAP_FAILED) {perror("mmap");close(fd);return 1;}// 修改内存中的内容为 "world"memcpy(addr, new_data, strlen(new_data));// 解除映射if (munmap(addr, sb.st_size) == -1) {perror("munmap");close(fd);return 1;}close(fd);return 0;
}