On Mon, Oct 23, 2023 at 10:45:44PM +0200, Thomas Schmitt wrote: > Greg Wooledge wrote: > > This is what's causing the loop to iterate more times than it should, > > and to re-process input. > > That's not what i see in my experiments. > I see stuttering output which first repeats the lines put out so far > before it adds a new line. > The getline() loop iterates as often as there are input lines.
Here's what I'm seeing. First, with a tiny two-line input file, I see three loop iterations: unicorn:~$ cat 12 1 2 unicorn:~$ ./foo < 12 1 num_read: 2 at line 1 2 num_read: 2 at line 2 2 num_read: 2 at line 3 unicorn:~$ That's the case where I used strace and saw the lseek() in the first child process (but not in any later child processes, which was even *more* confusing). Next, with a larger three-line input file: unicorn:~$ cat bar This is one line of a text file containing many lines of text. This is one line of a text file containing many lines of text. This is one line of a text file containing many lines of text. unicorn:~$ ./foo < bar This is one line of a text file containing many lines of text. num_read: 63 at line 1 This is one line of a text file containing many lines of text. num_read: 63 at line 2 This is one line of a text file containing many lines of text. num_read: 63 at line 3 This is one line of a text file containing many lines of text. num_read: 63 at line 4 This is one line of a text file containing many lines of text. num_read: 63 at line 5 This is one line of a text file containing many lines of text. num_read: 63 at line 6 This is one line of a text file containing many lines of text. num_read: 63 at line 7 This is one line of a text file containing many lines of text. num_read: 63 at line 8 [...] This is one line of a text file containing many lines of text. num_read: 63 at line 413 This is one line of a text file containing many lines of text. num_read: 63 at line 414 ^C unicorn:~$ I am fairly sure this would repeat indefinitely. I didn't let it go more than a few seconds, though. My system: Debian 12, Linux 6.1.0-13-amd64, gcc (Debian 12.2.0-14) 12.2.0, libc6:amd64 2.36-9+deb12u3.
