Linux df command doesn't show newly freed space

Recently I noticed that my web server (running Linux) was running out of disk space. So I proceeded to delete log files that were hundreds of megabytes big, but then executing the "df" (diskfree) command didn't show any change in available disk space. After some research it turned out that files currently open and are deleted will not release the free space until the process using it was stopped. I use the Apache web server so restarting httpd, and then doing a "df" showed the updated disk space data. In the future I will probably stop the web server first, delete the log file, and then start it up.