例题如下:
#include <stdio.h>
#define N 5
typedef struct student {
long sno;
char name[10];
float score[3];
} STU;
void fun(char *filename, long sno)
{ FILE *fp;
STU n; int i;
fp = fopen(filename,"rb+");
while (!feof(fp))
{ fread(&n, sizeof(STU), 1, fp);
if (n.sno==sno) break;
}
if (!feof(fp))
{ for (i=0; i<3; i++) n.score[i] += 3;
fseek(fp, -(long)sizeof(STU), SEEK_CUR);
fwrite(&n, sizeof(STU), 1, fp);
}
fclose(fp);
}
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}}, ss[N];
int i,j; FILE *fp;
fp = fopen("student.dat", "wb");
fwrite(t, sizeof(STU), N, fp);
fclose(fp);
printf("\nThe original data :\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");
}
fun("student.dat", 10003);
fp = fopen("student.dat", "rb");
fread(ss, sizeof(STU), N, fp);
fclose(fp);
printf("\nThe data after modifing :\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");
}
getchar();
}