/* handling arbitrary length lines on input */
#include <stdio.h>
#include <stdlib.h>

extern char *getline(FILE *fp);

int main() {
    char *line;

    while ((line = getline(stdin)) != NULL) {
       printf(":<%s>:\n",line);
       free(line);
    }
    return 0;
}

/*  Return next line without restrictions on line length and, like fgets(),
    return NULL if no characters read  and there was EOF or read error.
    Although a line longer than 256 chars cannot come directly from 
    a terminal, very long lines can come via redirection from files.
    For efficiency, extend line a CHUNK at a time instead of by a single char.
*/
#define CHUNK 80

char *getline(FILE *fp) {
    char *line = NULL;    /* points to beginning of line */
    int len_alloced = 0;  /* allocated length excluding \0 terminator */
    char *append_loc;     /* location for appending next CHUNK of chars */

    for (;;) {
       /* make space for next CHUNK of line and a \0 terminator) */
       line = realloc(line, (len_alloced += CHUNK) + 1);
       if (NULL == line) {fprintf(stderr,"Out of memory."); exit(1)}; 
       append_loc = line + len_alloced - CHUNK;

       /* After reading two CHUNKs YYYYYY and zzzzzz of size 6 the
	  the line array just before third fgets() would be:
	  YYYYYYzzzzzz******\0
	  ^           ^      ^     
	  line   append_loc  line+len_alloced
       */
        /* Read up to CHUNK chars starting at append_loc and \0 terminate */
        if (NULL == fgets(append_loc, CHUNK + 1, fp)) {
	   /* Read error  or  EOF encountered as first char */
	   if (len_alloced == CHUNK) { /* Nothing was read */
              free(line);
	      return NULL;
	   }
	   else return line; /* Had partial line when error or EOF occurred */
        }

        /* if line was not filled to end then reclaim space at end */
	if (strlen(append_loc) != CHUNK)
	   return realloc(line, strlen(line) + 1);
	/* if line is filled to end and is \n terminated */
        else if (line[len_alloced - 1] == '\n') return line;
	
        /* more of line yet to come - continue loop - rare if CHUNK large */
    }
}