Output to file is not flushing immediately

[Guest]

I have a perl script that writes stuff to a text file. While the
script is running, I do a "tail -f" on the text file to see the
output. But I can tell that the output isn't being flushed
immediately, because the script writes something to the file
immediately before sleeping for 60 seconds, but I don't see that
output show up in the "tail -f" until after it comes back from
sleeping.

I thought that putting a "\n" at the end of a print would do a flush,
but that's obviously not the case.

I also read that if you put "$| = 1" at the beginning of your script,
then it would do a flush after every print or write command. I tried
that, and it still does not flush.

 

[xhoster]

I have a perl script that writes stuff to a text file. While the
script is running, I do a "tail -f" on the text file to see the
output. But I can tell that the output isn't being flushed
immediately, because the script writes something to the file
immediately before sleeping for 60 seconds, but I don't see that
output show up in the "tail -f" until after it comes back from
sleeping.

I thought that putting a "\n" at the end of a print would do a flush,
but that's obviously not the case.

use IO::Handle;
#...
$fh->autoflush();

I also read that if you put "$| = 1" at the beginning of your script,
then it would do a flush after every print or write command. I tried
that, and it still does not flush.

That will only turn autoflush on for the STDOUT (or whatever the currently
selected filed handle is).

Read all about it here:
perldoc -q flush

Xho

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