Read line from file without knowing the line length

by

You can start with some suitable size of your choice and then use realloc midway if you need more space as:

int CUR_MAX = 4095;
char *buffer = (char*) malloc(sizeof(char) * CUR_MAX); // allocate buffer.
int length = 0;

while ( (ch != '\n') && (ch != EOF) ) {
    if(length ==CUR_MAX) { // time to expand ?
      CUR_MAX *= 2; // expand to double the current size of anything similar.
      buffer = realloc(buffer, CUR_MAX); // re allocate memory.
    }
    ch = getc(file); // read from stream.
    buffer[length] = ch; // stuff in buffer.
    length++;
}
.
.
free(buffer);

You’ll have to check for allocation errors after calls to malloc and realloc.

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