CODEWITHSUNDEEP
cfile
Brandyn
Brandyn

Reputation: 1017

Having trouble checking for newline when reading file

I'm trying to write a program to read a file of an unknown size / line size but I'm having some issues detecting the new line character.

When I run the program, it never reaches the end of the line point within the while loop in readFile and will just run constantly. If I run print each character, it prints out some unknown char.

I've tried setting ch to be an int value and typecasting to char for \n comparison. It's not reaching the EOF condition either so I'm not sure what is going on.

code:

void readFile(FILE* file)
{
    int endOfFile = 0;
    while (endOfFile != 1)
    {
        endOfFile = readLine(file);
        printf("%d\n", endOfFile);
    }
}

int readLine(FILE* file)
{
    static int maxSize = LINE_SIZE;
    int currentIndex = 0;
    int endOfFile = 0;
    char* buffer = (char*) malloc(sizeof(char) * maxSize);
    char ch;

    do
    {
        ch = fgetc(file);
        if ((ch != EOF) || (ch != '\n'))
        {
            buffer[currentIndex] = (char) ch;
            currentIndex += 1;
        }

        if (currentIndex == maxSize)
        {
            printf("Reallocating string buffer");
            maxSize *= 2;
            buffer = (char*) realloc(buffer, maxSize);
        }
    } while ((ch != EOF) || (ch != '\n'));

    if (ch == EOF)
    {
        endOfFile = 1;
    }

    parseLine(buffer);
    free(buffer);

    return endOfFile;
}

If someone could help me that would be greatly appreciated because I have been stuck on this issue for quite some time. Thanks in advance.

Upvotes: 1

Views: 54

Answers (2)

Malcolm McLean
Malcolm McLean

Reputation: 6406

Just use this boilerplate standard construct

int ch;  /* important, EOF is -1, not in the range 0-255 */
FILE *fp;

/* double brackets prevent warnings about assignment in if */
while ( (ch = fgetc(fp)) != EOF)
{
  /* we now have a valid character */

  /* usually */
  if(ch == endofinputIlike)
    break; 
}
/* here you have either read all the input up to what you like
  or skip because of EOF. usually you will set N or something, 
  or if N == 0 it was EOF, or we can test ch for EOF */

Generally assignment in if is a bad idea, but this particular snippet is so idiomatic that every experienced C programmer will instantly recognise it.

Upvotes: 0

blue112
blue112

Reputation: 56432

(ch != EOF) || (ch != '\n')

This is always true.

You want an && (AND) here, both in your if and while, otherwise it will never stop.

Upvotes: 5

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