set default window size and font in gVim

click on
edit>startup settings to edit the vimrc in windows

"set defautl window size
set lines=24
set columns=90
"set default font:size
set guifont=Courier\ New:h14

google C++ coding style

http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml

gen_ctags

# setting
WORKDIR=`pwd`
# get all file list
echo "get all file list"
rm ctags.Uranus ctags.utopia 2>/dev/null
find $WORKDIR/Uranus/ -name '*.[HhCc]' >> ctags.Uranus
find $WORKDIR/Uranus/ -name '*.cc' >> ctags.Uranus
find $WORKDIR/Uranus/ -name '*.cpp' >> ctags.Uranus
find $WORKDIR/utopia/ -name '*.[HhCc]' >> ctags.utopia
find $WORKDIR/utopia/ -name '*.cc' >> ctags.utopia
find $WORKDIR/utopia/ -name '*.cpp' >> ctags.utopia

# remove unwanted files

echo "remove unwanted files"
# Uranus
sed -i /Cus60/d ctags.Uranus
sed -i /eCospro/d ctags.Uranus
sed -i /Trunk/d ctags.Uranus
sed -i /u3/d ctags.Uranus
# utopis
sed -i /u2/d ctags.utopia
sed -i /u3/d ctags.utopia

sed -i /t2/d ctags.utopia
sed -i /t4/d ctags.utopia
sed -i /t7/d ctags.utopia
sed -i /t8/d ctags.utopia
sed -i /t9/d ctags.utopia
sed -i /t11/d ctags.utopia
sed -i /t12/d ctags.utopia
sed -i /t13/d ctags.utopia
sed -i /titania4/d ctags.utopia
sed -i /titania7/d ctags.utopia
sed -i /titania8/d ctags.utopia
sed -i /titania9/d ctags.utopia

sed -i /Janus/d ctags.utopia
sed -i /janus/d ctags.utopia
sed -i /j2/d ctags.utopia

sed -i /s7/d ctags.utopia
sed -i /s7j/d ctags.utopia
sed -i /s7ml/d ctags.utopia
sed -i /s7ld/d ctags.utopia
sed -i /s8/d ctags.utopia

sed -i /maria10/d ctags.utopia
sed -i /prans2/d ctags.utopia

sed -i /r2/d ctags.utopia

# generate tag file
cat ctags.Uranus ctags.utopia > ctags.files
echo "generate tag file"
ctags -L ctags.files
#cscope -b -q -k

# generate file list for Perforce
echo "generate file list for Perforce"
ESCSTR=$(echo "$WORKDIR" | sed -e 's/\//\\\//g')
echo $ESCSTR
echo "sed -e 's/$ESCSTR//g' ctags.files > ctags.p4"
sed -e "s/$ESCSTR//g" ctags.files > ctags.p4

# export global variable
echo "===== IMPORTANT ====="
echo "please export the following variable"
echo "export CTAGFILE=$WORKDIR/tags"

linux dump stace functions

1) dump_stack

vimrc

ab tl Tlist
ab tls TlistSync

where

Tlist is for ctag list
TlistSync is for syncing the ctag navigating window with the current cursor

compound statement expression

http://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html


wield stuff only for gcc, but useful

vimrc

syntax on
set nu
set ruler
set hlsearch
set cul
colorscheme evening
set vb
cs add cscope.out
set cscopetag
set foldmethod=marker
set tw=80
set ai
set nojoinspaces
set formatoptions=qtcor

"for C programming
ab #i #include
ab #d #define
ab #e #endif
ab #p #pragma
ab #m Min-Hua Chen

"spell check
ab sc set spell
ab nsc set nospell
"ab #c Author(s): xxx
"\Copyright (c) 2008 xxx
"\Permission to copy, modify, and distribute this program is granted


ab #c Author(s): xxx

autocmd BufReadPost *.c set cin
autocmd BufReadPost *.h set cin
autocmd BufReadPost *.pl set cin
autocmd BufReadPost *.cpp set cin
autocmd BufReadPost *.php set cin
autocmd BufReadPost *.py set si
autocmd BufReadPost *.java set si
autocmd BufReadPost *.java set cino+=j1
autocmd BufReadPost *.java set sw=4

Interesting set intersection by using 'uniq'

I was asked to find the intersection of two IP lists yesterday. I write a simple program with Perl. The program iterates the two lists to find the repeated IPs, which is a O(n^2) algorithm.

foreach $a (@A) {
    foreach $b (@B) {
        if ($a eq $b) {
        ...
        }
    }
}

When I wake up this morning, another way to do this pops onto my mind.

cat file-A | sort | uniq > tmp
cat file-B | sort | uniq >> tmp
cat tmp | sort | uniq -d

Basically, it is a O(nlog(n)) algorithm. (the sort operation).

X forwarding in ssh

To enable X forwarding, try the following command
ssh -X xxx.xxx.xxx.xxx

than we can launch a program with GUI through ssh.

Sometimes it does not work as expected, check the DISPLAY environment variable.

export DISPLAY=:10.0

duplicate a new table in Oracle

create table [new table name] as select * from [table name]

Remove VirtualBox lock

The lock file of VirtualBox is placed in
/tmp/.vbox-[user name]-ipc

default apache2 username on Debian

www-data

fighting with oci8 - apache2 + php5 + Oracle

Connecting to the Oracle database by using apache2 + php5 is simple -- if you already know all the traps along the way.

In order to connect to the Oracle database with my apache2 and php5, I've read several tutorials. Many thanks for them.

I want to talk about my experience -- everything is done correctly, but the phpinfo() still shows no oci8 information.

First, you should take a look at the error log of apache in /var/log.
In my case, my error log shows

PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php5/200 60613+lfs/oci8.so' - libaio.so.1: cannot open shared object file: No such fi le or directory in Unknown on line 0

The log already told me the answer, all I had to do is to install the lobaio.so. I did so and solved the problem.

Another way to discover the problem is to use the ldd command to exam the oci8.so.

linux-gate.so.1 => (0xb7fb3000)
libclntsh.so.11.1 => /opt/oracle/instantclient/libclntsh.so.11.1 (0xb627b000)
libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb610e000)
libnnz11.so => /opt/oracle/instantclient/libnnz11.so (0xb5ec0000)
libdl.so.2 => /lib/i686/cmov/libdl.so.2 (0xb5ebc000)
libm.so.6 => /lib/i686/cmov/libm.so.6 (0xb5e96000)
libpthread.so.0 => /lib/i686/cmov/libpthread.so.0 (0xb5e7d000)
libnsl.so.1 => /lib/i686/cmov/libnsl.so.1 (0xb5e64000)
/lib/ld-linux.so.2 (0xb7fb4000)
libaio.so.1 => not found

It showed the same problem.

rrdtool - every data is a rate!

This article is about understanding the rate calculating in the rrdtool.

I'm doing a SA project recently. We get the RTTs(round-trip time) by the ping command and write the RTT to a rrd file, print out the graph, ...

More information about the rrdtool can be found on their website.
http://oss.oetiker.ch/rrdtool/

I first created a rrd file:
rrdtool create F.rrd \
--step 10 \
DS:rtt1:GAUGE:20:0:U \
RRA:MAX:0.5:1:35712

Then, I updated some values to the F.rrd file. A interesting fact is that when I update the value at exact the time step (say 10, 20, 30, etc.), I'll have a accurate value.

# rrdtool update F 1262733290:3
# rrdtool update F 1262733300:4
# rrdtool update F 1262733310:5
# rrdtool update F 1262733320:6

1262733300: 4.0000000000e+00
1262733310: 5.0000000000e+00
1262733320: 6.0000000000e+00

OK, there is a thing called "heartbeat" in the rddtool, it helps the updates that occur at a not-accurate timestamps. For example, if we update a value at time 1262733331, the rrdtool will put the value to 1262733330. It's a nice feature, since there is always some delays in the networking world.

Let's take a look

# rrdtool update F 1262733331:7
# rrdtool update F 1262733340:8

1262733330: 7.0000000000e+00
1262733340: 7.9000000000e+00

As you can see, the value 7 is updated at 1262733331 but is shifted to 126273330 in the rrd file. But what happened with the next update at 1262733340? We update 8 but the rrd file recorded 7.9. Strange, right?

Here is how 7.9 comes out: since rrdtool treats every data as a rate, if there are more than one samples before a time step, rrdtool tries to calculate the average rate of all the samples before the time step (after the previous time step, of course).

previous time step: 1262733330
when we update 7 at 1262733331; 8 at 1262733340.
the calculation is
(7 * (1262733331 - 1262733330) +
8 * (1262733340 - 1262733331) ) / 10 = 7.9

Here is a figure to help understanding:


OK, Let's do the math with another example:

# rrdtool update F 1262733341:54
# rrdtool update F 1262733342:3
# rrdtool update F 1262733347:31
# rrdtool update F 1262733350:3

To find out the average value at 1262733350:
previous time step: 1262733340
(54 * (1262733341 - 1262733340) +
3 * (1262733342 - 1262733341) +
31 * (1262733347 - 1262733342) +
3 * (1262733350 - 1262733347)) / 10 = 22.1

Read the rrd file to verify our answer:
1262733350: 2.2100000000e+01

It's a perfect match. :-)

I hope this article can help someone who has the same question as I did.