待读入文件

1.greenteemo

2.csdn

3.blog

代码，详细说明见注释

#include #define LENGTH_OF_LINE 1024

int main(){

FILE *fp = fopen("file.txt", "r"); // 打开文件

char line[LENGTH_OF_LINE];

while( fgets(line, LENGTH_OF_LINE, fp) ){

printf("%s\n", line); // 读取文件内容

}

// back to beginning of file

// 当前文件指针指向文件末尾

printf("=== back to beginning of file ===\n");

rewind(fp); // 回到文件最开头

fgets(line, LENGTH_OF_LINE, fp); // 读入第一行，此时文件指针指向第二行开头

printf("current line : %s\n", line);

// back to beginning of line

printf("=== back to beginning of line ===\n");

fgets(line, LENGTH_OF_LINE, fp); // 读入第二行，此时文件指针指向第三行开头

long offset = ftell(fp); // 记录第三行开始的位置与文件开头的偏置值

fgets(line, LENGTH_OF_LINE, fp); // 读入第三行，此时文件指针指向文件末尾

printf("current line :%s\n", line);

fseek(fp, offset, SEEK_SET); // 根据offset回到第三行开头

fgets(line, LENGTH_OF_LINE, fp); // 读入第三行，此时文件指针指向文件末尾

printf("current line :%s\n", line);

return 0;

}

输出

1.greenteemo

2.csdn

3.blog

=== back to beginning of file ===

current line : 1.greenteemo

=== back to beginning of line ===

current line :3.blog

current line :3.blog