How to move to a specific position in the file? Use fseek Example: Copy 5 bytes

Question

How to move to a specific position in the file? Use fseek Example: Copy 5 bytes from the file testl.dat, starting at the tenth byte, and append to the end oftest2.dat: % Create files test1.dat and test2.dat % % Each character uses 8 bits (1 byte) fid1 = fopen(1est 1.dat', 'w+') fwrite(fid1, " ABCDEFGHIJKLMNOPQRSTUVWXYZ'); fid2 = fopen ('test2.dat', 'w^+'); fwrite (fid2, 'Second File'); % Seek to the 10th byte ('j)' read 5 fseek(fid1, 9, bof'); A = fread(fid 1, 5, 'uint delta = > char'); felose(fid 1); % Append to test2 dat fseek (fid2, 0, 'eof); fwrite(fid2, A); fclose(fid2)

Explanation / Answer

Seek to 10th byte:

fp = fopen( "test1.dat", "rb");
fseek(fp, 10, SEEK_SET);

Then read:

char *pointer_to_string = (char *) malloc( sizeof(char) * 6 );
fread(pointer_to_string, sizeof(char), 5, fp);

and close the first file:
fclose(fp);

To append simple do:

FILE *fp2 = fopen( "test2.dat", "a+");
fwrite(pointer_to_string, sizeof(char),5,fp2);

You must do this also:
#include <stdio.h>

At the end don't forget to:
free(pointer_to_string);

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