From: ts <decoux@...>
Date: 2003-09-09T22:46:43+09:00
Subject: Re: IO#clone and 1.6 -> 1.8 question

>>>>> "d" == dblack  <dblack@superlink.net> writes:

d> I always get 20 lines of output.  But when I clone fh, I start to get
d> the behavior where one fh advances to EOF and the other doesn't.  I'm
d> afraid I'm still not seeing why cloning a file handle would or should
d> cause any of this to happen.

 With your original example

d>   fh = File.new("nums")  # 'nums' is 1..20, one integer per line
d>   puts fh.gets
d> 
d>   fd = fh.clone
d>   puts fd.gets
d> 
d>   puts fh.gets

 it do this (well with some more tests :-)))

svg% cat nums
1
2
3
4
5
6
7
8
9
svg% 

svg% cat a.c
#include <stdio.h>

main()
{
    FILE *f1, *f2;
    char line[1024];

    f1 = fopen("nums", "r");
    line[0] = line[1] = line[2] = 0;
    fread(line, 1, 2, f1);
    printf("%s", line);
    fseeko(f1, 0L, SEEK_CUR);
    f2 = fdopen(dup(fileno(f1)), "r");
    line[0] = line[1] = 0;
    fread(line, 1, 2, f2);
    printf("%s", line);
    line[0] = line[1] = 0;
    if (fread(line, 1, 2, f1) == 0) {
        printf("EOF\n");
    }
    else {
        printf("%s", line);
    }
}
svg% 

svg% a.out
1
2
EOF
svg% 


Guy Decoux