C - Strings in Structures returning whole array

Question

I'm trying to store characters read from a file into an array of characters, but it ends up storing every succeeding character as well. For this code, I created a structure and a function to initialize the array.

From "Structures.h"

typedef struct (
    int size;
    char *elem;
    } cvector;

From "Utilities.c"

cvector make_cvector (int size)
    {   cvector temp;
        temp.size = size;
        temp.elem = calloc(size, sizeof(char));
        return temp;
    }

Then I'm trying to read a text file that says: "a b c"

In the body, I stated: (where nPtr is the pointer for opening the file)

cvector NodeID;
NodeID = make_cvector(3);
for(i=0;i<3;i++){
        fscanf(nPtr,"%s", &NodeID.elem[i]);
        printf("%s ",&NodeID.elem[i]);
}

This results in " a b c " But right after this loop, I typed another loop:

for(i=0;i<3;i++)
        printf("%s ", &NodeID.elem[i]);

Resulting to "abc bc c" When in fact I want "a" "b" and "c" stored separately. There's probably something wrong with my initialization or pointers, but I've been trying to read up online to no avail. Where could the error be? Thank you!

Simon · Accepted Answer · 2013-10-07 03:26:48Z

2

You are printing a string when what you really want to do is printing a single character. Replace

printf("%s ",&NodeID.elem[i]);

by

printf("%c ",NodeID.elem[i]);

and it should work.

answered Oct 7, 2013 at 3:26

Simon

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3 Comments

user2853084 Over a year ago

Thank you for that and I understand the error. However, the printing was just a means to demonstrate my problem. The real problem I encountered was in a latter part where I put: if(strcmp(LoadLoc, &NodeID.elem[j])==0) which basically never happened. I suppose the error then isn't with initialization, but with the use of "strcmp" what would be a suitable alternative? :D I'll try to search online as well. Thank you very much sir!

Simon Over a year ago

LoadLoc is a string containing a single character, right? If so then store LoadLoc in a char instead and do if (LoadLoc == NodeID.elem[j])

user2853084 Over a year ago

Thanks! This worked, but I wanted to maintain a certain level of universality as some parts of the program might shift to comparing strings and not just characters. Anyway, I solved the problem by initializing them as "cmatrix" instead of "cvector" where the 1st dimension is an array of strings, and the second dimension an array of characters per string. Thanks for all the help! :D

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