Re: [newbie] deleting contents of a file
Craig-- Many people suggested removing the file and then recreating a new empty file. While not difficult, that does take a little more time. Your method is much simpler and very quick. I just tried it on a log file and it works great. Can anyone give me a reason why this method might cause problems? Well, it's just been pointed out that it doesn't actually EMPTY the file per se. It actually creates a one-byte file. I believe that the 'echo' command prints the string argument given it, plus a newline on the end. That newline gets into the new file, so you actually have a file that isn't empty, but contains a single newline character. As long as you don't actually need this file to be totally emptied to zero bytes, and don't mind a blank line at the top of the file, this should work fine. I haven't seen the permissions issue that Jose mentions at all, in all my fooling with this the permissions are preserved. So maybe he's seeing something we're not. -- Dan Ray Director Custom Applications Triangle Research, Inc. http://www.triangleresearch.com
Re: [newbie] deleting contents of a file
JOse-- #tail oldfile oldfile Clever! Although, of course, the question was EMPTYING the file, not cutting it down to the last 10 ines... Actually, I don't see why redirecting output from tail would have any different effect on the target file than redirecting output from echo. Shouldn't both be simple stdout redirects into oldfile? Shouldn't both have the same effect on oldfile's permissions? -- Dan Ray Director Custom Applications Triangle Research, Inc. http://www.triangleresearch.com
Re: [newbie] deleting contents of a file
* Dan Ray [EMAIL PROTECTED] [010710 06:14]: Well, it's just been pointed out that it doesn't actually EMPTY the file per se. It actually creates a one-byte file. I believe that the 'echo' command prints the string argument given it, plus a newline on the end. That newline gets into the new file, so you actually have a file that isn't empty, but contains a single newline character. As long as you don't actually need this file to be totally emptied to zero bytes, and don't mind a blank line at the top of the file, this should work fine. I haven't seen the permissions issue that Jose mentions at all, in all my fooling with this the permissions are preserved. So maybe he's seeing something we're not. As Ray says, the echo myfile method works fine regarding ownership and permissions, but leaves a newline in the file. If you want a zero-length file, why not: echo -n myfile this tells 'echo' not to follow the (empty) string with a newline, so the resulting file is zero length. I just tested this on Mdk 8.0 to be sure. -- Jan Wilson, SysAdmin _/*]; [EMAIL PROTECTED] Corozal Junior College | |:' corozal.com corozal.bz Corozal Town, Belize | /' chetumal.com linux.bz Reg. Linux user #151611 |_/ Network, SQL, Perl, HTML
Re: [newbie] deleting contents of a file
Jan-- echo -n myfile this tells 'echo' not to follow the (empty) string with a newline, so the resulting file is zero length. Aha! Just what I didn't know I was looking for! This command is my new nominee for best way to do it. -- Dan Ray Director Custom Applications Triangle Research, Inc. http://www.triangleresearch.com
Re: [newbie] deleting contents of a file
Bascially you want a file, like a log, that had tons of data in it, to have all the data removed, but there still be a log file there? Does that sound about right? What I would do, would be delete the file rm -f file.log And then to get the file there again, with the bit size of 0 (zero) I'd use the touch command. touch file.log If you then get a ls -la on the file, it will give you this. [timh@r2d2 timh]$ touch file.log [timh@r2d2 timh]$ ls -la file.log -rw-r--r--1 timh timh0 Jul 9 08:09 file.log That's how I would go about it. Others would open the file in NEdit and then just delete everything and save it. All depends on how ya want to go about doing it. tdh -- T. Holmes - UNIXTECHS.org [EMAIL PROTECTED] - Real Men Us Vi! Uptime: 8:08AM up 4 days, 11:15, 5 users, load averages: 0.01, 0.05, 0.02 Your Fortune Of course it's the murder weapon. Who would frame someone with a fake? | * Craig Westerman [EMAIL PROTECTED] [010708 23:47]: | Is there a linux command that will remove the contents of a file, but | leave the file name? | | To empty a text file named file.txt, I would do: | | $ cp /dev/null file.txt | | There are probably quite a few other ways to do it. | | -- | Jan Wilson, SysAdmin _/*]; [EMAIL PROTECTED] | Corozal Junior College | |:' corozal.com corozal.bz | Corozal Town, Belize | /' chetumal.com linux.bz | Reg. Linux user #151611 |_/ Network, SQL, Perl, HTML | | --
Re: [newbie] deleting contents of a file
Craig-- On Monday 09 July 2001 01:20 am, Craig Westerman wrote: Is there a linux command that will remove the contents of a file, but leave the file name? Echo an empty string into it: $ echo '' filename.txt That '' is a pair of single-quotes, incidentally. It's sort of hard to see that in some fonts... -- Dan Ray Director Custom Applications Triangle Research, Inc. http://www.triangleresearch.com
RE: [newbie] deleting contents of a file
There probably is, but I don't know it.. I use : rm filename touch filename that removes the file and recreates it... regards Frank -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Craig Westerman Sent: Monday, 9 July 2001 1:21 PM To: Mandrake Newbie Subject: [newbie] deleting contents of a file Is there a linux command that will remove the contents of a file, but leave the file name? Thanks HW
RE: [newbie] deleting contents of a file
Using echo effectively creates a new file with new permissions. My preference is to use tail to tail the file over itself. I.E. #tail oldfile oldfile This preserves all existing permissions and ownerships. -JMS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Craig Westerman Sent: Monday, July 09, 2001 11:27 PM To: Mandrake Newbie; [EMAIL PROTECTED] Subject: RE: [newbie] deleting contents of a file Dan, Many people suggested removing the file and then recreating a new empty file. While not difficult, that does take a little more time. Your method is much simpler and very quick. I just tried it on a log file and it works great. Can anyone give me a reason why this method might cause problems? Thanks Craig [EMAIL PROTECTED] Craig-- On Monday 09 July 2001 01:20 am, Craig Westerman wrote: Is there a linux command that will remove the contents of a file, but leave the file name? Echo an empty string into it: $ echo '' filename.txt That '' is a pair of single-quotes, incidentally. It's sort of hard to see that in some fonts... -- Dan Ray Director Custom Applications Triangle Research, Inc. http://www.triangleresearch.com
[newbie] deleting contents of a file
Is there a linux command that will remove the contents of a file, but leave the file name? Thanks HW
