cleaning out a file

Simplicus has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: cleaning out a file by turnstep (Parson) on Apr 28, 2000 at 01:24 UTC
Nope. But you could do this: `open(X, ">$filename");` [download] or even: `perl -e "open(X, '>'.shift);" SYSTEM.DA0` [download] which would shrink SYSTEM.DA0 to 0 bytes....	[reply] [d/l] [select]
RE: Re: cleaning out a file by perlmonkey (Hermit) on Apr 28, 2000 at 02:49 UTC
Yes, I think this is the safest way. `close FH if open FH, ">".$filename` But overwrite mode might do an unlink/link combo. (meaning that the file $filename might be deleted, then recreated as a empty file). So this could be the same as`unlink $filename; open ">$filename";` I am not sure. Anybody actually know if there is a difference? The file inode number should still be the same though for either method. Depending on what you are doing this is probably good enough.	[reply] [d/l] [select]
RE: RE: Re: cleaning out a file by Anonymous Monk on Apr 28, 2000 at 04:59 UTC
perlfunc:open says the file is truncated, not unlinked.	[reply]
RE: cleaning out a file by Anonymous Monk on Apr 28, 2000 at 11:24 UTC
`system("cat /dev/null>$file");` also not very portable	[reply] [d/l]
Re: cleaning out a file by blackwolf (Sexton) on Apr 28, 2000 at 20:50 UTC
What about plain ol' ... truncate 'filename', 0;	[reply]
Re: cleaning out a file by clash (Novice) on Dec 01, 2000 at 23:53 UTC
why dont u just unlink it and create it again?	[reply]
Re: cleaning out a file by kirbyk (Friar) on Apr 28, 2000 at 02:38 UTC
Another easy way to do it would be: `unlink($filename); system("touch $filename");` [download] touch is a standard unix command that updates the last-modified timestamp of a file. If the file doesn't exists, it creates it as a zero-byte file. It's a handy little thing to know, for testing purposes. -- Kirby	[reply] [d/l]
RE: Re: cleaning out a file by turnstep (Parson) on Apr 28, 2000 at 05:32 UTC
Actually, 'touch' does a lot more than that. Most people only use it for its default behavior, but it can change the access and modification times to anything you want - which can be occassionally very useful. For the record, using a system("touch") is not very portable, especially when you can do the same thing in perl easy enough.	[reply]
RE: cleaning out a file by radixzer0 (Beadle) on Apr 28, 2000 at 02:33 UTC
Hate to introduce a non-perl item ;) but a bash one-liner is: `: > filename` [download] Use the tools you've got is what i always say... This also preserves all the file permissions and attributes... Assuming you're on Unix of course (or bash on some other platform).	[reply] [d/l]


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