files and strings in C??

[myalani]

Hi

I have a question regarding this code. This code is supposed to extract ASCII values from the input in the file testme.txt (which only contains: KMN) and then convert every character to ASCII (K = 75. M = 77, etc..) but for some reason the code only converts the first character.
I want to use fscanf only.

#include <stdio.h>
int main(void){
    char ac;
    FILE *inp, *outp;
    inp = fopen("testme.txt","r");
    outp = fopen("testme.out","w");
    fscanf(inp,"%c",&ac);
    printf("The number read from the file is %d.\n",ac);
    fprintf(outp,"ASCII was %d.\n",ac);
    fclose(inp);
    fclose(outp);
    return (0);
}

[laserlight]

The reason is that you only read the first character

You could read the characters in a loop instead, ending when EOF is reached. Since you don't appear to have any special formatting requirements, it probably makes more sense to use fgetc instead of fscanf for this.

[Babkockdood]

It only reads the first value because you only tell it to read the first value, fscanf is only called once. You need to use a loop.

inp = fopen("testme.txt", "r");
outp = fopen("testme.out", "w");
int x;
while ((x = fgetc(inp)) != EOF) {
    printf("%d ", x);
    fprintf(outp, "%d ", x);
}
printf("\n");
fprintf(outp, "\n");
fclose(inp);
fclose(outp);

fgetc() returns a character from a file stream. In the context in which you're only looking for character input, you should use fgetc() instead of fscanf(). fscanf() works, but fgetc() is more efficient. Since I put the x assignment inside the while loop's conditional, x is assigned once every time the loop repeats, and fgetc will return the next character in the stream. The while loop is essentially saying:

read a character
if character is not the end-of-file indicator (EOF),
    print character in decimal form to stdout
    print character in decimal form to outp

Read this for more info: For, While and Do While Loops in C - Cprogramming.com