read a line until a newline or EOF, allocating and resizing an array as necessary

read_line.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define READ_LINE_BUFFER 1024

char *read_line(FILE *f)
{
	char *line, *l;
	size_t linelen;
	char buf[READ_LINE_BUFFER];
	size_t len;

	line = NULL;
	linelen = 0;

	while (!feof(f) && !ferror(f)) {
		if (!fgets(buf, (READ_LINE_BUFFER), f)) break;
		len = strlen(buf);
		l = realloc(line, linelen + len + 1);
		if (!l) {
			if (line) free(line);
			return NULL;
		}
		line = l;
		strcpy(line+linelen, buf);
		linelen += len;
		if (line[linelen-1] == '\n') {
			break;
		}
	}

	return line;
}