(w)dstat

wdstat

In my .profile (on CentOS 5, just in case there were some changes in dstat) I have following alias to dstat (wdstat stands for Wawrzek's dstat):

alias wdstat="dstat -lcpymsgdn 5"

Where the options stands for:

• -l  - UNIX load (1m   5m  15m) load average in 1, 5 and 15 minutes, respectively;
• -c - cpu stats (usr sys idl wai hiq siq) percent of time spent in user and system space, idle, waiting on resource,  serving interrupts and softirqs (software interrupts);
• -p - process stats (run blk new) number of running, blocked and newly created processes;
• -y - system stats (int   csw) - number of interrupts and context switches;
• -m - memory stats (used  buff  cach  free) amount of memory used by processes, disk buffers, disk cache and free;
• -s - swap stats (used  free) - amount of used and free swap space;
• -g - page stats (in   out) number of page put in and out from swap;
• -d -disk stats (read  writ) - number of reads and writes from all disks;
• -n -network stats (recv  send) number of received and send network packages;

Further reading:

• http://dag.wiee.rs/home-made/dstat/
• http://www.teamquest.com/pdfs/whitepaper/ldavg1.pdf
• http://www.linuxhowtos.org/System/procstat.htm
• http://lwn.net/Articles/520076/
• http://en.wikipedia.org/wiki/Paging#Linux

netstat, ports, hosts and awk glue

Recently, I needed to create a list of all servers connected on a given port (in following example port 80). I used a mixture of awk and other UNIX command line tools.

netstat -nt| \
 awk -F':'\
   '$5==80 {count[$8]++} \
   END{ for (i in count) { \
      cmd="host "i; \
      cmd |& getline j; \
      split(j, a, " "); \
      printf "%40s - %d\n", a[5], count[i]}}'| \
 sort -n -k 3

First netstat provided the list of all connection (netstat -nt); -n stands for numeric and -t for only TCP connections.

Next awk, with the ':' defined as a field separator (awk -F':'), used lines where local port was 80 ($5==80) to create an associated array with a key define by connected host ip and a value equal to  number of connection from it ({count[$8]++}). At the end of the script execution, awk looped over all element of the array (END{for (i in count)).  Next there was a crux of the script, the cmd was define as a run the OS host command with the awk variable i as an argument  (cmd="host" i). The |& operator created two-way pipe between awk and a execution of the previously defined cmd. The getline command was used to store cmd output into the variable j (cmd |& getline j). Next the split command split the content of the  j into separate words and saved them into the a array (split(j, a, " ")). Finally the printf formatted output (printf "%40s - %d\n", a[5], count[i])).  The actual hostname was fifth element of the a.

For continence, output lines were sorted by numeric order on third column  (sort -n -k 3). Each output line consisted of a hostname ,'-' and a number - e.g. important.com - 3456.