UNIX for Dummies Questions & Answers

Hi All,

I want to check if one my log file is updating properly, how can I achieve it.
The approach I am trying is to get the file size at two different interval and than comparing it eg :

Code:

[puttyuser@voda_ggn ~]$ ls -ltr | tail -1 | awk '{print $5}'
20480

If you are trying to get information about a file, why not ask about that file explicitly with:

Code:

ls -l File

instead of hoping that:

Code:

ls -ltr DirectoryContainingFile | tail -1

will give you information about the file you want???

Why not use stat (or equivalent, if available)?

Hi Don,

Thanks for your info but this is the log file and a new file gets create after exceeding a certain size limit, in this way I am sure to get the size of latest file

Code:

ls -ltr DirectoryContainingFile | tail -1 | awk '{print $5}'

@RudiC - I have never used stat, let me try to find how it works.

The stat command utility is available mostly on Linux distributions.

Code:

sfile=/tmp/logsize
size=`ls -ltr | tail -1 | awk '{print $5}'`
if test -f $sfile &&
 read osize < $sfile &&
 test $osize = $size
then
 echo "logfile not growing"
fi
echo $size > $sfile

Some considerations.

Most modern kernels maintain a memory cache of pages written to files. The dirty (changed or added data) pages get written to disk physically - when the system does a fflush (or equivalent) call. Which is not always RIGHT NOW. Also file mtime and atime updates may be deferred until the file descriptor is actually closed. All of this is kernel-dependent and depends what kind of file system is in use (plus mount options).

What this means:
1. Please post your OS name and version
2. the fstab or vfstab (in /etc ) entry for your filesystem.

Why?

The answers given will very probably work for you, but may not always be both timely and correct, which is what you seem to want. Constant runs of RudiC's nice little script may not show you that data was sent by the logging program to the log - until a cache flush occurs. This may be every 30 seconds or so, whenever your sync daemon runs. If you have one. That is why we ask those two questions.