ifconfig output

What does all the counters in the ifconfig output mean? e.g. frame, dropped... this page describe some of them.

eth1      Link encap:Ethernet  HWaddr 02:83:13:02:24:00
          inet addr:192.168.20.13  Bcast:0.0.0.0  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2169 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1769 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1009774 (986.1 KiB)  TX bytes:210912 (205.9 KiB)

cat << EOF

Here is an option for writing several line of text to a file via a the shell.


~ # cat > test << EOF
> this is first line
> this is the second line
> EOF
~ # cat test
this is first line
this is the second line
~ #

Pipe stdout and stderr to one file.

In the Linux shell you can pipe both stdout and stderr to a file with > output_file 2>&1
E.g.:

 memtester 16M 1 > /dev/null 2>&1

Chain linux commands together

In the Linux shell you can chain a number of command together. You can do a number of command after each other without having to wait for each command to end.

e.g.
touch memtester ; memtester 16M 1 ; rm memtester

The commands is here separated with ; which tells the shell to execute the first command and then it is done it should execute the next command etc.

Another example:
touch memtester && memtester 16M 1 && rm memtester

Here the commands are separated with && which tells the shell to execute the first command and if it completes successfully then execute the next command and etc.

test -s

The test -s command behaves a bit different on Cygwin and Linux. In Linux it can be OK to use test -s to test for a directory, because it size if different from 0. But in Cygwin the test fails because directories in Cygwin have the size 0.

Understanding the Linux load average

I was examine /proc/loadavg today, but how to interpret it? I found this fine post describing the content:
http://juliano.info/en/Blog:Memory_Leak/Understanding_the_Linux_load_average