How to use fscanf to put strings into an array?

Question

So I am using fscanf to read from a file, and I am trying put those strings into an array. It seems to work but I'm only getting the last string into my array. When i try to print it, I'm only print the characters of my last string. I didn't include my method because it doesn't effect what fscanf does in case anyone got confused. Also, my CMDLINE file has the following strings foo barr tar 526-4567 456-8792.

output is :

456-8792
56-8792
6-8792

etc...

Here is the code:

int main (int argC, char *argV[]) {
    FILE *fp;
    int index;
    int ret;
    char str[1000];

    //Need at least 2 files to begin program
    if (argC < 3) {
        fprintf(stderr, "Usage: %s file\n", argV[0]);
        exit(1);
    }//if statemtn

    //check to see if the CMDLINE file is in the arguements
    ret = scanC(argC, argV);

    //if no CMDLINE file is found, print error and exit
    if (ret == 1) {
        fprintf(stderr, "you must provide a CMDLINE file\n");
        exit(1);
    }

    //iterate and open CMDLINE file and read from it
    for (index = 0; index < argC; index++) {
        if (strcmp(argV[index], "CMDLINE") == 0) {
            fp = fopen(argV[index], "r");
            //error check
            if (fp == NULL) {
                fprintf(stderr, "Counld not open file %s\n", argV[index]);
                exit(1);
            }//if statment

            //read from fscanf and put it's arguements into an array
            while (!feof(fp)) {
                char *p2 = str;
                //scan the strings of the file into str array
                while (fscanf(fp, "%s", p2) != EOF) {
                    p2++;
                }//while loop 2
            }//while lop 1

            //close the file for it is not needed to be open anymore
            fclose(fp);
        }//if statement
    }//for looop

    char *p;
    p = str;
    int j;
    for (j = 0; j < strlen(str); j++) {
        printf("%s\n", p);
        p++;
    }
    return 1;
}

Take a look to [Why is “while ( !feof (file) )” always wrong?](http://stackoverflow.com/questions/5431941/why-is-while-feof-file-always-wrong) — David Ranieri, Nov 02 '16 at 22:05

Barmak Shemirani · Answer 1 · 2016-11-03T00:06:32.397

char *p;
p = str;
int j;
for (j = 0; j < strlen(str); j++) 
{
    printf("%s\n", p);
    p++;
}

You have one string, example "abcd", you can just print it as printf("%s\n", str); Instead you are printing the same string starting at different offsets. Result is as follows:

abcd
bcd
cd
d

Perhaps you are confused between "character array" and "array of strings"

//This will reserve 100 character arrays, or 100 strings
char *arr[100];

int count = 0;
while (fscanf(fp, "%999s", str) == 1)
{
    arr[count] = malloc(strlen(str) + 1);
    strcpy(arr[count], str);
    count++;
    if (count == 100)
        break;
}

int i;
for (i = 0; i < count; i++) 
    printf("%s\n", arr[i]);

In real world application you use malloc and realloc to allocate array of strings large enough to read the file.

score 1 · Answer 2 · answered Nov 02 '16 at 22:27

you can use a marker to set the "current character":

char *p2 = str;
size_t k = 0;
size_t pos = 0;
//scan the strings of the file into str array at position pos
while((k = fscanf(fp, "%s", p2 + pos)) != EOF){
    // update pos
    pos += k;
    p2++;
}//while loop 2

This will enable to store the whole file in your string PROVIDED IT IS LESS THAN 1000 CHARACTERS! otherwise just add a safeguard in the while loop.

How to use fscanf to put strings into an array?

2 Answers2