每天进步一点点-->函数fseek() 用法
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转自于:http://blog.csdn.net/wl_soft50/article/details/7787521
在阅读代码时,遇到了很早之前用过的fseek(),很久没有用了,有点陌生,写出来以便下次查阅。
函数功能是把文件指针指向文件的开头,需要包含头文件stdio.h
fseek
- #include <stdio.h>
- long filesize(FILE *stream);
- int main(void)
- {
- FILE *stream;
- stream = fopen("MYFILE.TXT", "w+");
- fprintf(stream, "This is a test");
- printf("Filesize of MYFILE.TXT is %ld bytes\n", filesize(stream));
- fclose(stream);
- return 0;
- }
- long filesize(FILE *stream)
- {
- long curpos, length;
- curpos = ftell(stream);
- fseek(stream, 0L, SEEK_END);
- length = ftell(stream);
- fseek(stream, curpos, SEEK_SET);
- return length;
- }
- #include <stdio.h>
- #define N 5
- typedef struct student {
- long sno;
- char name[10];
- float score[3];
- } STU;
- void fun(char *filename, STU n)
- {
- FILE *fp;
- fp = fopen(filename, "rb+");
- fseek(fp, -1L*sizeof(STU),SEEK_END);
- fwrite(&n, sizeof(STU), 1, fp);
- fclose(fp);
- }
- void main()
- {
- STU t[N]={ {10001,"MaChao", 91, 92, 77}, {10002,"CaoKai", 75, 60, 88},
- {10003,"LiSi", 85, 70, 78}, {10004,"FangFang", 90, 82, 87},
- {10005,"ZhangSan", 95, 80, 88}};
- STU n={10006,"ZhaoSi", 55, 70, 68}, ss[N];
- int i,j; FILE *fp;
- fp = fopen("student.dat", "wb");
- fwrite(t, sizeof(STU), N, fp);
- fclose(fp);
- fp = fopen("student.dat", "rb");
- fread(ss, sizeof(STU), N, fp);
- fclose(fp);
- printf("\nThe original data :\n\n");
- for (j=0; j<N; j++)
- {
- printf("\nNo: %ld Name: %-8s Scores: ",ss[j].sno, ss[j].name);
- for (i=0; i<3; i++)
- printf("%6.2f ", ss[j].score[i]);
- printf("\n");
- }
- fun("student.dat", n);
- printf("\nThe data after modifing :\n\n");
- fp = fopen("student.dat", "rb");
- fread(ss, sizeof(STU), N, fp);
- fclose(fp);
- for (j=0; j<N; j++)
- {
- printf("\nNo: %ld Name: %-8s Scores: ",ss[j].sno, ss[j].name);
- for (i=0; i<3; i++)
- printf("%6.2f ", ss[j].score[i]);
- printf("\n");
- }
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