How to avoid garbage values while writing to a file - file

Question

i am trying to create a record keeping random access file in C. As you know, in random access file, all the records are given a fixed standard byte length. so that they can be accessed randomly when needed using fseek() and fread() functions. Here i have kept that length as size of whole structure, which is 90 bytes. i have multiple character arrays in structure. when i get input from user in those arrays of characters using structure object, and pass that object to the fwrite function and i give size as size of structure, the character array data is written to the file. but because the text from user is mostly is less than 30 chracters mostly( max size of array), the fwrite function writes the string from user in file but also writes garbage values in file for those indexes which were not used in array. if i use fseek and fread() functions, the program reads data fine. but i want my file to be garbage values free and human readable. How can i do that?
`#include <stdio.h>
#define size 30
struct Record{
char account[size];
char name[size];
char address[size];
};
int main()
{
FILE *ptr = NULL;
ptr = fopen("testfile.txt", "w");
if (ptr == NULL)
{
printf("Could not open file.");
}
else
{
struct Record client;
char account[30];
char name[30];
char address[30];
printf("Enter account number: ");
gets(client.account);
printf("Enter name: ");
gets(client.name);
printf("Enter address: ");
gets(client.address);
fwrite(&client, sizeof(struct Record),1,ptr);
fclose(ptr);
ptr = fopen("testfile.txt", "r");
char buffer[size];
fseek(ptr,0,SEEK_SET);
fread(buffer,30,1,ptr);
puts(buffer);
fclose(ptr);
}
puts("Done!");
return 0;
}`
The data in file i am getting is of follwing form (input: 1 jack new york):
1 ((± 0(± /Œ¬¨þa òpv ± jack ‚Ž ((± 0(± 0(± ¤þnew york lþa à# €# 4(±
I think the problem above is due to the larger size given than length of strings. i also tried giving size as length of string. In that case, the garbage values were not printed. but in that case i will lose my principle of keeping each record of same length to have random access property in file. So how can i write my string data to file without writing garbage values and yet keep the length of each record same as standard lentgh we have decided.

Answer 1

I just recently found the solution to my problem. It was to place space characters ' ' after terminating character in the array. for example, if I have an array of size 30 and I have given it a string of only 10 characters, with the terminating character at the 11th position, I can store space in the remaining ones. so that when I write a whole string with size 30 in the file, the space characters are written and we do not get garbage values appearing in our file. instead, we will have our strings readable in the file.
I used this function for this purpose:
void spaces(char array[],int size)
{
int length = strlen(array);
for (int i = length + 1; i < size; i++)
{
array[i] = ' ';
}
}