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how to get the correct reading of diskspace

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Operating Systems Linux how to get the correct reading of diskspace
# 1  
Old 09-09-2008
Error how to get the correct reading of diskspace
What has happened.

I beleive the diskpace is not showing the correct reading.

Is there another command to use to get the diskspace without using du -h?


Is there another command linux uses.

The reason i am assuing this i cleared the log of a process that started using nohup for example.

nohup script1.sh > script1.log 2>&1


Now the script1.log was consuming all the diskspace

So while the process is still running i cleared the log using cat /dev/null > script1.sh then ran rm -rf script1.sh

after this was done the diskspace is remaining the same size even though the file removed was at least 20% to 30% use of diskspace.

Currently I cannot kill the script at the moment as it is a n important script. So i just wanted to know if there is a work around to get the correct disk size without killing the process in the mean time.

Any help would be appreciated.
# 2  
Old 09-09-2008
The space remains occupied while the process holds the file handle open.
# 3  
Old 09-09-2008
Do you know of way to rotate the log file controlled by nohup? That way i will not have to clear it in the future.
# 4  
Old 09-10-2008
I'm sorry, but I don't think it can be done. Hmm, that would actually be a rather useful helper application to have: cat with "close and reopen output file" when sent a signal. Maybe such a thing exists, but you would have to use it when starting the job.
# 5  
Old 09-10-2008
Quote:
Originally Posted by jonathan184
So while the process is still running i cleared the log using cat /dev/null > script1.sh then ran rm -rf script1.sh
I presume you meant script1.log, not script1.sh.

Sometimes the cat /dev/null > script1.log (or just >script1.log on its own) is enough. When the next output is written to the file you can end up with a sparse file, where the file size is reported as quite large, but the file only occupies a small space on disk.

The big problem was that you removed the log file with rm, which meant that you could no longer truncate the log.

Here is an example where I create a "log" file, and part way through writing to it, I "flatten" the file. You can see that the file size continues to increase, but the disk usage reported by du drops:

Code:
# while sleep 1 ; do dd if=/dev/zero bs=1048576 count=1 2>/dev/null ; done > /tmp/logfile &
[1]     20489
# ls -l /tmp/logfile
-rw-r--r--   1 root       sys        2097152 Sep 10 07:15 /tmp/logfile
# ls -l /tmp/logfile ; du -ks /tmp/logfile
-rw-r--r--   1 root       sys        8388608 Sep 10 07:15 /tmp/logfile
11264   /tmp/logfile
# ls -l /tmp/logfile ; du -ks /tmp/logfile
-rw-r--r--   1 root       sys        9437184 Sep 10 07:15 /tmp/logfile
11264   /tmp/logfile
# ls -l /tmp/logfile ; du -ks /tmp/logfile
-rw-r--r--   1 root       sys        15728640 Sep 10 07:15 /tmp/logfile
27648   /tmp/logfile
# ls -l /tmp/logfile ; du -k /tmp/logfile
-rw-r--r--   1 root       sys        23068672 Sep 10 07:15 /tmp/logfile
27648   /tmp/logfile
# > /tmp/logfile
# ls -l /tmp/logfile ; du -k /tmp/logfile
-rw-r--r--   1 root       sys        33554432 Sep 10 07:15 /tmp/logfile
3072    /tmp/logfile
# ls -l /tmp/logfile ; du -k /tmp/logfile
-rw-r--r--   1 root       sys        35651584 Sep 10 07:15 /tmp/logfile
11264   /tmp/logfile
# ls -l /tmp/logfile ; du -k /tmp/logfile
-rw-r--r--   1 root       sys        36700160 Sep 10 07:15 /tmp/logfile
11264   /tmp/logfile
# kill %1
#
[1] + Terminated               while sleep 1 ; do dd if=/dev/zero bs=1048576 count=1 2>/dev/null ; done > /tmp/logfile &
#

# 6  
Old 09-10-2008
Cool explaination thank you. That makes sense on what you said.
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