linux - Read/Write to binary files in C -

does have example of code can write binary file. , code can read binary file , output screen. looking @ examples can write file ok when try read file not outputting correctly.

reading , writing binary files pretty same other file, difference how open it:

unsigned char buffer[10]; file *ptr;  ptr = fopen("test.bin","rb");  // r read, b binary  fread(buffer,sizeof(buffer),1,ptr); // read 10 bytes our buffer 

you said can read it, it's not outputting correctly... keep in mind when "output" data, you're not reading ascii, it's not printing string screen:

for(int = 0; i<10; i++)     printf("%u ", buffer[i]); // prints series of bytes 

writing file pretty same, exception you're using fwrite() instead of fread():

file *write_ptr;  write_ptr = fopen("test.bin","wb");  // w write, b binary  fwrite(buffer,sizeof(buffer),1,write_ptr); // write 10 bytes our buffer 

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since we're talking linux.. there's easy way sanity check. install hexdump on system (if it's not on there) , dump file:

mike@mike-virtualbox:~/c$ hexdump test.bin 0000000 457f 464c 0102 0001 0000 0000 0000 0000 0000010 0001 003e 0001 0000 0000 0000 0000 0000 ... 

now compare output:

mike@mike-virtualbox:~/c$ ./a.out  127 69 76 70 2 1 1 0 0 0 

hmm, maybe change printf %x make little clearer:

mike@mike-virtualbox:~/c$ ./a.out  7f 45 4c 46 2 1 1 0 0 0 

hey, look! data matches now^*. awesome, must reading binary file correctly!

^{*note bytes swapped on output data correct, can adjust sort of thing}