Sort,uniq (string, int) columns in csv files

cat file

text1,5
text4,3
text3,1
text1,4
text7,2
text3,7
text2,9

1. less file | sort -u -t, -k1,1 - sort the first column and get unique texts

text1,5

text2,9

text3,1

text4,3

text7,2

2. less file | sort -u -t, -k1,1 | sort -t, -k2 -nr - get unique texts on first column and reverse order for the second column using -r option

text2,9

text1,5

text4,3

text7,2

text3,1

Download a web site using wget

wget -r --level=0 -convert-links --page-requisites --no-parent <URL>
httrack <URL>

Remove a folder except some files

mkdir folder1
touch file1, file2, file3, file4
rm -rf -- !(@(file1|file2)*)

“cd -” to toggle between the last two directories

ubuntu1004@ubuntu1004:~$ cd /tmp/tmp1/tmp2/tmp3
ubuntu1004@ubuntu1004:/tmp/tmp1/tmp2/tmp3$ cd /tmp/tmp10/tmp20/tmp30
ubuntu1004@ubuntu1004:/tmp/tmp10/tmp20/tmp30$ cd -
/tmp/tmp1/tmp2/tmp3
ubuntu1004@ubuntu1004:/tmp/tmp1/tmp2/tmp3$ cd -
/tmp/tmp10/tmp20/tmp30
ubuntu1004@ubuntu1004:/tmp/tmp10/tmp20/tmp30$ cd -
/tmp/tmp1/tmp2/tmp3
ubuntu1004@ubuntu1004:/tmp/tmp1/tmp2/tmp3$

mkdir on subfolders and cd

Add in .bash_profile
function mkdircd () { mkdir -p "$@" && eval cd "\"\$$#\""; }


ubuntu1004@ubuntu1004:~$ mkdircd /tmp/tmp1/tmp2/tmp3
ubuntu1004@ubuntu1004:/tmp/tmp1/tmp2/tmp3$ pwd
/tmp/tmp1/tmp2/tmp3

CDPATH defines base directory for cd command

ubuntu1004@ubuntu1004:~$ pwd
/home/ubuntu1004
ubuntu1004@ubuntu1004:~$ cd init.d
bash: cd: init.d: No such file or directory
ubuntu1004@ubuntu1004:~$ export CDPATH=/etc
ubuntu1004@ubuntu1004:~$ cd init.d
/etc/init.d
ubuntu1004@ubuntu1004:/etc/init.d$ pwd
/etc/init.d
ubuntu1004@ubuntu1004:/etc/init.d$

- change permanent, add export CDPATH=/etc to your ~/.bash_profile

- you can add more than one directory entry in the CDPATH variable, separating them with ':' 

export CDPATH=.:~:/etc:/var