CODEWITHSUNDEEP
asynchronousraku
Christopher Bottoms
Christopher Bottoms

Reputation: 11168

How can I read from the standard error of another program, line by line?

This program catches all of the standard error from another program, but it sometimes gives me a partial line:

#!/bin/env perl6

my $proc = Proc::Async.new('./print_to_stderr');

$proc.stderr.tap( -> $str {
    for $str.lines() {
        put "Captured ERR: $_";
    }
});

my $promise = $proc.start;

await $promise;

Using ./print_to_stderr:

#!/bin/env perl6

for ^10 {
    $*ERR.put: "($_): Howdee";
}

Just now, I got the following output:

Captured ERR: (0): Howdee
Captured ERR: (1): Howdee
...
Captured ERR: (6): Howdee
Captured ERR: (7): Howde
Captured ERR: e
Captured ERR: (8): Howdee

As you see, for item 7, the standard error was broken up between two different taps. But I'd like it to wait and give me a whole line.

Update: This was reproducible for me using Rakudo Star 2017.04, but this isn't an issue in Rakudo Star 2017.07 as pointed out by Elizabeth Mattijsen below.

Upvotes: 2

Views: 127

Answers (1)

Elizabeth Mattijsen
Elizabeth Mattijsen

Reputation: 26969

Which version of Rakudo Perl 6 are you using? I cannot reproduce this issue. In any case, Supply.lines should not give you incomplete lines, ever. So if this is happening on the most recent version of Rakudo Perl 6, this should be reported as a bug.

Upvotes: 3

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