C reading binary files
binaryfiles, c, file
Solution
`feof(fp)` becomes false (i.e. non-zero value) only if you tried to read past the end of file. That should explain why the loop is entered one more than what you expect.
From the documentation:
The function feof() tests the end-of-file indicator for the stream
pointed to by stream, returning nonzero if it is set. The end-of-
file indicator can be cleared only by the function clearerr().
Also read the post: Why is “while ( !feof (file) )” always wrong?
Problem
Possible Duplicate: “while( !feof( file ) )” is always wrong If I write an array to the output file and I close the file, then open the file again and read everything until end-of-file is reached, although the file contains only 4 number, the program will read and print 5 numbers, why? Program output: ``` a[0] = 4 a[1] = 7 a[2] = 12 a[3] = 34 a[4] = 34 ``` save.bin (with a hex editor) ``` 04000000 07000000 0C000000 22000000 ``` ``` #include <stdio.h> #include <stdlib.h> #define path "save.bin" int main(void) { FILE *f=NULL; int a[]={4,7,12,34},i,n=4,k; f=fopen(path,"wb"); if(f==NULL) { perror("Error"); exit(1); } for(i=0;i<n;i++) // or I could use fwrite(a,sizeof(int),n,f); fwrite(&a[i],sizeof(int),1,f); fclose(f); f=fopen(path,"rb"); if(f==NULL) { perror("Error"); exit(1); } i=0; while(!feof(f)) { fread(&k,sizeof(int),1,f); printf("a[%d] = %d\n",i,k); i++; } printf("\n"); fclose(f); return 0; } ```