Of course, $|= 1; won't do the slightest good here. There is nothing Perl can do to unbuffer the output of the tail command that it is reading from (just to be clear).

We are lucky that Perl often makes "writing your own replacement" relatively easy. You are lucky that you've "never had to do too much to work around it". Rewriting every command in the pipeline in Perl can be a lot of work or may not be possible.

Most of the time we are lucky in that the output flows fairly continuously until EOF and so the buffering at most introduces a slight delay (and, in theory, makes the process go faster, though I'm suspicious of such pre-optimization thinking and suspect you'd be hard pressed to notice an efficiency difference between line buffering and full buffering).

It is still rather silly and sad that such a simple feature that would be trivial to add a tiny bit of external control to and has caused so much grief over the previous decades hasn't been addressed. If I already had my fingers in GNU source code, I'd certainly submit a patch to the trivial: 

    setvbuf( STDOUT, NULL, isatty(1) ? _IOLBF : _IOFBF, BUFSIZE );

[download]

To do something more like: 

    {
        char* bufPref= getenv( "CRTL_STDOUT_BUF_MODE" );
        int   bufMode=
            NULL == bufPref
                ? ( isatty(1) ? _IOLBF : _IOFBF )
                : "L"==*bufPref ? _IOLBF : "F"==*bufPref ? _IOFBF : _I
+ONBF;
        }
        setvbuf( STDOUT, NULL, bufMode, BUFSIZE );
    }

[download]

- tye        

In reply to Re^3: Using pipe and reading from the stdin (buffering) by tye
in thread Using pipe and reading from the stdin by mellin

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