一些有用的shell

1.平级切换目录eg：从/a/b/c/kk  切换到 /a/b/f/kk 

cd ${PWD/c/f}  #主要是shell的字符串替换    

2.随机生成一个ip

echo $((RANDOM%256)).$((RANDOM%256)).$((RANDOM%256)).$((RANDOM%256))

3.this will fill your shell with random data, parts of it highlighted  （偷懒专用）

cat /dev/urandom | hexdump -C |grep --color=yes -E "(ca|fe|3d|42|e1|b3|ae|f8)" | perl -MTime::HiRes -pne "Time::HiRes::usleep(rand()*1000000)"    

4.Selecting a random file/folder of a folder random file from files in directory

ls -1 | shuf -n 1

5.随机生成合法的mac地址

python -c "from itertools import imap; from random import randint; print ':'.join(['%02x'%x for x in imap(lambda x:randint(0,255), range(6))])"

for i in {1..6}; do printf "%0.2X:" $(($RANDOM % 0x100 )); done | sed 's/:$/\n/'

for i in {1..6}; do printf "%0.2X:" $[ $RANDOM % 0x100  ]; done | sed 's/:$/\n/' 

                

h=0123456789ABCDEF;for c in {1..12};do echo -n ${h:$(($RANDOM%16)):1};if [[ $((c%2)) = 0 && $c != 12 ]];then echo -n :;fi;done;echo

            

 6.将一个字符串split 成数组：
awk:echo ‘a s d a da daa’  |awk '{split($0,arr);print arr[1]}'
herestring: read -a ARR <<< "a s d a da daa";echo ${ARR[2]}         

7.让自己的终端显示时间

                

export PS1="(\@) $PS1"

8.Create date-based tgz of current dir, runs in the background, Here is the full alias

alias tarred='( ( D=`builtin pwd`; F=$(date +$HOME/`sed "s,[/ ],#,g" <<< ${D/${HOME}/}`#-%F.tgz); tar --ignore-failed-read --transform "s,^${D%/*},`date +${D%/*}.%F`,S" -czPf "$"F "$D" &>/dev/null ) & )'
                

9.显示bash 256种颜色所对应的数值
for i in {0..255}; do echo -e "\e[38;05;${i}m${i}"; done | column -c 80 -s '  '; echo -e "\e[m"　　

10.模拟黑客帝国的字符屏幕 :)[Blue Matrix]
while [ 1 -lt 2 ]; do i=0; COL=$((RANDOM%$(tput cols)));ROW=$((RANDOM%$(tput cols)));while [ $i -lt $COL ]; do tput cup $i $ROW;echo -e "\033[1;34m" $(cat /dev/urandom | head -1 | cut -c1-1) 2>/dev/null ; i=$(expr $i + 1); done; done

                    

11.快速查阅date 日期表示帮助文档
alias dateh='date --help|sed "/^ *%a/,/^ *%Z/!d;y/_/!/;s/^ *%\([:a-z]\+\) \+/\1_/gI;s/%/#/g;s/^\([a-y]\|[z:]\+\)_/%%\1_%\1_/I"|while read L;do date "+${L}"|sed y/!#/%%/;done|column -ts_'
             

12.迅速搭建webserver (在文件传输方面能派上用场，wget curl)
python -m SimpleHTTPServer  
Serve current directory tree at

13.This command will start a simple SMTP server listening on port 1025 of localhost. This server simply prints to standard output all email headers and the email body. 

python -m smtpd -n -c DebuggingServer localhost:1025