fwrite add new line after each input

Question

I wanted to add a new line to separate each entry in the file.

I tried:

show_dump(buff + "\n", len, dump_fd);

But got an error with that.

I got this function from somewhere else, It formats the buffer sent from the client into hex and ASCII data.

/*
Usage:
    show_dump(buffer, buffer_length, stdout);
    show_dump(buffer, buffer_length, fd);
*/

#include <string.h>



void show_dump(unsigned char *data, unsigned int len, FILE *stream) {
    const static char       hex[] = "0123456789abcdef";
    static unsigned char    buff[67];   /* HEX  CHAR\n */
    unsigned char           chr,
                            *bytes,
                            *p,
                            *limit,
                            *glimit = data + len;

    memset(buff + 2, ' ', 48);

    while(data < glimit) {
        limit = data + 16;
        if(limit > glimit) {
           limit = glimit;
           memset(buff, ' ', 48);
        }

        p     = buff;
        bytes = p + 50;
        while(data < limit) {
            chr = *data;
            *p++ = hex[chr >> 4];
            *p++ = hex[chr & 15];
            p++;
            *bytes++ = ((chr < ' ') || (chr >= 0x7f)) ? '.' : chr;
            data++;
        }
        *bytes++ = '\n';

        fwrite(buff, bytes - buff, 1, stream);
     }
}

This is how I'm creating the file:

if(dump) {
    add = dumpfile;

    for(i = 1; ; i++) {
        sprintf(add, "%d.log", i);
        dump_fd = fopen(dumpfile, "rb");
        if(!dump_fd) break;
        fclose(dump_fd);
    }
    dump_fd = fopen(dumpfile, "wb");
    if(!dump_fd) std_err();

}

And this is how I'm writing into the file:

if(dump_fd) show_dump(buff, len, dump_fd);

---

Question: Whats wrong with the code? Why is the files all written together and not line by line?

Answer 1

I guess you could just add the '\n' to the buffer:

buff[strlen(buff)]='\n';
buff[strlen(buff)+1]='\0';

should work, I think.

-Edit:

Or like pointed out in the comments (and probably a better solution..), use strcat:

strcat(buff,"\n");

and if needed encapsulate it with an if-statement to prevent overflows:

if (sizeof(buff) > strlen(buff)+1)