Clearing the content of files by size

Question

Considering if I list files in a directory:

drwx--x--x 43 root wheel 4.0K Aug 18 12:52 ..
-rw-------  1 root root  268K Aug 18 04:31 build_locale_databases_log
-rw-------  1 root root  5.2M Aug 18 17:21 access_log
-rw-------  1 root root   85K Aug 18 17:14 cpbackup_transporter.log
-rw-------  1 root root  2.1M Aug 18 05:49 cphulkd.log
-rw-------  1 root root  3.2M Aug 18 17:19 error_log
-rw-------  1 root root  1.7M Aug 18 12:52 license_log

Here I want to clear the contents of the files which are greater than 2Mb. (i.e) to make the file size to zero bytes for the following files:

access_log
cphulkd.log
error_log

Answer 1

I like to answer the direct question first, but do not run this before reading to the end of my answer. The command you are asking for (which may not be what you want) is:

find /wherever -type f -name '*.log' -size +4096 -print \
    | xargs truncate --size 0

Note that the +4096 means files with more than 4096 512-byte sectors. The problem is that if these are log files that a process is actively writing to, those processes will keep their position in the file. You'll recover the disk space (assuming your file system supports sparse files, which most do), but when you go to look at your logs there will be blocks of zeros at the beginning. So you really need to restart your daemon right after doing this, or better yet move the files out of the way and restart your daemons:

cd /wherever
find . -name '*.log' -maxdepth 1 -size +4096 -exec mv {} {}.old \;
systemctl restart yourservice (or whatever you need to restart)
rm -f *.old

Answer 2

You can do this by a find command:

for i in $(find . -type f -size +2097152c);do  cat /dev/null > $i;done

The find command find . -type f -size +2097152c will find all files of size greater than

2MB (2097152 bytes)

The for loop will loop into the list of the files it got in the find command and will clean them out with a cat /dev/null

------Edit------

As suggested by user3188445 You can try this way also

for i in $(find . -type f -size +2097152c);do  :  > $i;done

Answer 3

Posixly:

find . ! -name . -prune -type f -size +2097152c -exec sh -c '
  for f do
    : > "$f"
  done
' sh {} +

With GNU find or BSD find:

find . -maxdepth 1 -type f -size +2M ...

Answer 4

while read -r line; do
    truncate -s 0 $line
done < <(find / -type f -name '*.log' -size +2M)

Answer 5

I came up with:

find . -type f -size '+2M' -print | while read i
do
echo " " > $i
done

which works.