// Redhat
I am running a cron with cp every 15 minutes.
cp /p2/arch/log/* /p2/bkp
What I need is to not to copy the file again if the filename already exists under /p2/bkp
The reason is that the file size under /p2/arch/log/ will be reduced (contents truncated), so I need to keep the files copied over for the very 1st time.
In that case, I keep the original files w/o losing the contents.
Please advise.
Hi.
You can use the -n or --no-clobber options.
Note, however, that if a file is being written into /p2/arch/log/file when the cron job starts running, you might copy the initial contents of file to /p2/bkp/file and never pick up data written to the end of the file after the copy completes.
Are files in /p2/arch/log being updated after all of the data that is initially written to them has been completed? If not and /p2/arch/log and /p2/bkp are on the same filesystem, did you consider just making a hard link from /p2/arch/log/file to /p2/bpk/file ?
Pardon, a link as a backup??
If there is a risk that a file is being written during the backup then I would rather ensure the files are a minute old
find /p2/arch/log -type f -mmin +0 -name '*' -exec cp -n {} /p2/bkp \;
Sorry... I should have been much more verbose about the environment needed to use a hard link as a backup method.
I once worked in a group where a logging daemon was started when the system booted and ran forever to log errors that would occur. It opened the log files with something like:
fd = open(logname, O_CREAT | O_WRONLY, S_IRUSR | S_IRGRP | S_IROTH);
(note that it is opening a file for writing with no write permissions on the file it creates).
If the open() failed with an EPERM error, it looked to see if another daemon is already running (and quietly exited if it was). Otherwise, it incremented that day's log sequence number and tried again.
At midnight, it closed the current log file, opened a new log file for the new day, hard linked any log files created the previous day to a backup directory, and removed any log files in the log directory that were more than a week old (leaving the link in the backup directory untouched).
Another process ran every few days archiving the log files in the backup directory to tape and removing log files more than three months old from the backup directory.
This scheme worked well for that project, but it assumes a lot about how the logs are created and used that is atypical for most loggers today.
cp -n or cp -no
Flag doesn't work.
Which Flag should I use?
Try `cp --help' for more information.
cp: invalid option -- n
Try `cp --help' for more information.
[root@]# cp --help
Usage: cp [OPTION]... [-T] SOURCE DEST
or: cp [OPTION]... SOURCE... DIRECTORY
or: cp [OPTION]... -t DIRECTORY SOURCE...
Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.
Mandatory arguments to long options are mandatory for short options too.
-a, --archive same as -dR --preserve=all
--backup[=CONTROL] make a backup of each existing destination file
-b like --backup but does not accept an argument
--copy-contents copy contents of special files when recursive
-d same as --no-dereference --preserve=link
-f, --force if an existing destination file cannot be
opened, remove it and try again
-i, --interactive prompt before overwrite
-H follow command-line symbolic links
-l, --link link files instead of copying
-L, --dereference always follow symbolic links
-P, --no-dereference never follow symbolic links
-p same as --preserve=mode,ownership,timestamps
--preserve[=ATTR_LIST] preserve the specified attributes (default:
mode,ownership,timestamps), if possible
additional attributes: context, links,
xattr, all
-c same as --preserve=context
--no-preserve=ATTR_LIST don't preserve the specified attributes
--parents use full source file name under DIRECTORY
-R, -r, --recursive copy directories recursively
--remove-destination remove each existing destination file before
attempting to open it (contrast with --force)
--sparse=WHEN control creation of sparse files
--strip-trailing-slashes remove any trailing slashes from each SOURCE
argument
-s, --symbolic-link make symbolic links instead of copying
-S, --suffix=SUFFIX override the usual backup suffix
-t, --target-directory=DIRECTORY copy all SOURCE arguments into DIRECTORY
-T, --no-target-directory treat DEST as a normal file
-u, --update copy only when the SOURCE file is newer
than the destination file or when the
destination file is missing
-v, --verbose explain what is being done
-x, --one-file-system stay on this file system
-Z, --context=CONTEXT set security context of copy to CONTEXT
--help display this help and exit
--version output version information and exit
By default, sparse SOURCE files are detected by a crude heuristic and the
corresponding DEST file is made sparse as well. That is the behavior
selected by --sparse=auto. Specify --sparse=always to create a sparse DEST
file whenever the SOURCE file contains a long enough sequence of zero bytes.
Use --sparse=never to inhibit creation of sparse files.
The backup suffix is `~', unless set with --suffix or SIMPLE_BACKUP_SUFFIX.
The version control method may be selected via the --backup option or through
the VERSION_CONTROL environment variable. Here are the values:
none, off never make backups (even if --backup is given)
numbered, t make numbered backups
existing, nil numbered if numbered backups exist, simple otherwise
simple, never always make simple backups
As a special case, cp makes a backup of SOURCE when the force and backup
options are given and SOURCE and DEST are the same name for an existing,
regular file.
Assuming that you just want to copy files from the directory /p2/arch/log (and not from subdirectories of that directory), you could try something like the following. It is untested, but should come close to what you were trying to do:
cd /p2/arch/log
for f in *
do [ -f "$f" ] || continue # If this isn't a regular file, skip it.
[ -e "/p2/bkp/$f" ] && continue # If a backup already exists, skip it.
cp "$f" /p2/bkp # Make a backup copy.
done
This should work with any shell based on Bourne shell syntax (e.g., ash , bash , dash , ksh , sh , zsh , etc.), but will not work with csh and its derivatives.
Another possibility:
rsync --ignore-existing /p2/arch/log/* /p2/bkp/
I think Scott was talking of the shell's noclobber option which works on redirections but not for cp .
No, this option is in GNU cp/coreutils version 8
man cp
...
-n, --no-clobber
do not overwrite an existing file (overrides a previous -i option)
...
Thank you!!!
It works charming. Appreciate it!