Thread: null terminated strings

Presumably his VB file has fixed-length records, with fields padded with spaces (or with some other character) on the right. So it is essentially a binary file.
I think he just wants to read these strings into a C program and ensure they are null-terminated (removing the padding) to work as standard C strings.
I assume he wants to write them back out in the same fixed record format since he mentions "reversing the process". This would entail adding the padding characters back.
Alternatively he could write them back out as a text file, each field terminated by a newline. The records wouldn't be seekable then, but that would not really be a problem unless the file is very large.

kc8oye, could you run the following program on your file with a command like:
$ dumpit data.dat 256
The $ is your command line prompt; dumpit is whatever you call the dump program; data.dat is your data file; 256 is the number of bytes to dump. The program also allows a third parameter to skip a certain number of bytes first. A COUNT of 0 means to print the whole file. So dumpit data.dat 0 256 would output all but the first 256 bytes.
Try dumping the first 256 bytes. Then we can see exactly what the data looks like, and in particular what the padding characters are.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
 
int main(int argc, char **argv) {
    if (argc < 2 || argc > 4) {
        fprintf(stderr, "Usage: %s FILENAME [COUNT [SKIP]]\n", argv[0]);
        return 1;
    }
 
    int count = 0, skip = 0;
    if (argc > 2) {
        count = atoi(argv[2]);
        if (count < 0) count = 0;
        if (argc > 3) {
            skip = atoi(argv[3]);
            if (skip < 0) skip = 0;
        }
    }
 
    FILE *fin = fopen(argv[1], "rb");
    if (!fin) {
        perror("Cannot open input file");
        return 1;
    }
    if (skip > 0) fseek(fin, skip, SEEK_SET);
 
    int c, n = 0;
    char line[17] = {0};
 
    printf("%06X  ", skip);
    while ((count == 0 || n < count) && (c = fgetc(fin)) != EOF) {
        printf("%02X ", c);
        line[n % 16] = isprint(c) ? c : '.';
        if (++n % 16 == 0)
            printf(" |%s|\n%06X  ", line, skip + n);
    }
 
    if (n % 16 != 0) {
        line[n % 16] = '\0';
        printf("%*s |%s|", (16 - n % 16) * 3, " ", line);
    }
    putchar('\n');
 
    fclose(fin);
 
    return 0;
}