stop lose track with cp

Linux:

# -p to preserve ownership and permissions
cp -p x y
# even better if you have this alias in your .bashrc
alias cp="cp -p"

When working in a team, it is very important to preserve the information when you copy files around. It is very easy to lose track where the files are from, and who owns it. When we have to make duplicate copies of the same thing, make sure you use “-p”.

do it in colour in bash

bash:

# many bash script supports coloured output, it really helps if you are searching
# for something either a word or a directory from tens even hundreds of output
ls --color
grep --color

find all your files or directories on disk

bash:

# find all your files and directories
find / -user user_name 2>/dev/null
# find all your directories
find / -user user_name -type d 2>/dev/null

list ports being used by which program

linux:

lsof -i -n -p

remote desktop access from linux

bash:

# remote desktop access to remote windows servers
rdesktop rdp.remote.server.com

You may need to install rdesktop first from your favorite package manager. If you don’t know how to install it, you can find some instruction here

install sun-java in ubuntu

bash:

# add to repository list Ubuntu 10.4/10.10
sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner"
sudo apt-get update
sudo aptitude install sun-java6-jdk
sudo update-java-alternatives -s java-6-sun

change a number value in a text file

bash:

# this example will increase the integer value of a text file, e.g. value=1234 to value=1235
awk '/^value=/{ str=$0; sub("value=", "", str); n=strtonum(str); n++; print "value=" n; skip=1;} {if(!skip) {print $0;} skip=0;}'

remove / delete files using wildcard pattern when too many files in command line

bash:

# if we want to delete files whose names start with "tmp", normally we do as:
rm tmp*
# however, when there are too many files, bash will complain that there are too many files in list, then you can do
find . -maxdepth 1 -name "tmp*" -delete
# if you actually want to delete recursively, remove -maxdepth
find . -name "tmp*" -delete

ldd to find out program’s dependences

linux:

# ldd can display which .so library the program will use
ldd ./program

avoid accidental deletion by rm

bash:

# rm option -i will ask you every time it delete a file, you can also add this line to your .bashrc
alias rm="rm -i"
# in a research environment, most of time you have plenty of space, you can disable rm at all
alias rm="echo"