Check Open FDs (File Descriptors)

Very simple bash script
Check total open file descriptors and compare with percent of
maximum allowance by kernel
There is default values. So script do not need any args
but you can customize:
-w - warning level in number of FDs
-W - warning level in % to kernel limit (default = 75%)
-c - critical level in number of FDs
-C - critical level in % to kernel limit (default = 90%)
wW < cC

Script uses logic from this page:
http://www.netadmintools.com/art295.html

Output of cat /proc/sys/fs/file-nr on differen kernels
3391 969 52427 # For kernels <= 2.4.X
2323 0 141241 # For kernels >= 2.6.X
| | |
| | maximum open file descriptors (LIMIT)
| total free allocated file descriptors
total allocated file descriptors
(the number of file descriptors allocated since boot)
The number of open file descriptors is column 1 - column 2
In new kernel column 1 - is what we need.
use 1 - 2 for backcompatibility.

If problems and too much opened files you can increase allowance

echo "104854" > /proc/sys/fs/file-max