Steve1150 wrote: You would think the 5 venues that I posted my ls -s question on before posting on spiceworks would have resulted in someone pointing out that this was not a good way to prove the results of truncate. I'd like to limit the size of the file by occasionally copying the current file to a new name and truncating it. You can always delete the file and recreate the file, which might work in most cases. How can I use bash shell commands to do this? The file is 1 byte large, and takes the space needed to hold that one byte. Or, at least, very unlikely.
So in the end, I went off on the wrong track trouble shooting my root problem. The deleted file will have a deleted next to it. But this is not a good idea. Btw, your app, is it a stand-alone, web app,. How can one remove such a file, even though a process has it open? If you don't know the pid, and are looking for deleted files, you can do: lsof -nP grep ' deleted ' lsof -nP +L1, is an even better more reliable and more portable option list files that have fewer than 1 link.
At the moment, I only used the redirect methods I mentioned at the start of my post. How does one find large files that have been deleted but are still open in an application? Is there somewhere else that I would expect to see the error, say in a log file somewhere? While you could do that with your own script, it is a good idea to at least try using an existing working solution, in this case logrotate, which can do exactly that and is reasonably configurable. How can this be done? I know the reason, and I can fix it. You'll need to use pclose instead of close when you're done with the pipe. Or you could hack the kernel, but I would advise against that. Instead of open ing the file, use popen to open a pipe to an external program. Since you probably do not mind it, be my guest and use these commands.
It is used to shrink the size of a file to a desired size. This works at least in bash since it creates all the redirections required although only the last one will catch any input or none in this case. Method 1: Truncate a file using truncate command The safest way to truncate a log file is using the truncate command. They sort of work, but the resulting file is not empty, but rather it is a file that contains a single newline character. I have used this in the past to increase the size of a file and now after upgrading to the latest version of Ubuntu 11. Or delete it and somehow associate the process' stdout with a new file? Truncating the file as Stephane suggests might help, but the real outcome will also depend on your file system for example pre-allocated blocks will likely be freed only after you close the file in any case. We will use the size 0 zero to empty the file.
The impact on app performance should be quite small, but you'll have to run some tests. The tee example with several files should work in any case given your tee does know how to handle several output files Of course, the good old shell loop would work as well: for f in file1 file2. Let me show you some of these methods. How to clear a file from all of its content without deleting the actual file? Testing an app that does something particular. Ars may earn compensation on sales from links on this site. That should be a bit more reliable than grepping. In my experience, other tools are faster, simpler and safer for the vast majority of cases where people use dd.
The truncation process basically removes all the contents of the file. This will create a new empty file, if one does not exist. If you're mapping this file to memory, you may not have the expected performance. So, how do you empty a file in Linux? You can have a small pool or a large pool, it's your choice. If a new filename is specified, the function first attempts to close any file already associated with stream third parameter and disassociates it.
The rationale behind this behaviour is that the kernel wouldn't know what to do with data requests both read and write, but reading is actually more critical targeting such a file. If you have bucketloads of disk and you should, given its low price , there's no issue. This is especially true about log files, which often contains a large amount of outdated data. Unfortunately, the answer is not as straight-forward as one might assume. I downloaded and compiled the latest coreutils so I could have truncate available. What you see above is what I seen on my screen as I type those commands.
So, you need to kill the application that is writing to that file before truncating it. Is there another way to do this? Most Linux systems also have , which only works on certain file systems such as btrfs, ext4, ocfs2, and xfs , but is the fastest, as it allocates all the file space creates non-holey files but does not initialize any of it. You would move the old file to a permanent name, first. Anyone know if the linux command truncate has dropped support for padding zeros to the end of a file. If it's any help, I'm using RedHat and an Ubuntu linux systems. Thinking that I might take advantage of the truncate function man 2 truncate in Darwin I compiled this and ran it against two files, one of trivial size and the other the actual log file. Should you need to do it for several files, the safe way is truncate -s 0 file1 file2.
However, since logfiles are usually useful, you might want to compress and save a copy. This is not just relegated to log files, but could also happen to output files or any other file as well. I don't know how to make a process stop writing to its file descriptor without terminating it. When I try this on a file of trivial size, it does work. In Linux actually all unicies files are created when they are opened and deleted when nothing holds a reference to them.