###awk 2 lines into 1 line:

ifconfig | awk 'ORS= NR%2 ? " " : "\n" { print }'

print row 2 column 3:

ifconfig | awk 'NR == 2 { print $3 }'

###grep
do not show “a”:

ifconfig | grep -v 'a'

show 2 line after context:

ifconfig | grep -A 2 "inet"

show 1 line before context:

ifconfig | grep -B 1 "inet"

###test
if file exist then run commands

test -e .bashrc && source .bashrc

###${} ${var##/}:该命令的作用是去掉变量var从左边算起的最后一个’/’字符及其左边的内容
${var##.}:该命令的作用是去掉变量var从左边算起的最后一个’.’字符及其左边的内容

#：表示从左边算起第一个
%：表示从右边算起第一个
##：表示从左边算起最后一个
%%：表示从右边算起最后一个
＊：表示要删除的内容

###查看某个进程的线程(Check threads of a process):

1. $ ps -T -p <pid>
2. $ top -H -p <pid>

###网络相关信息:

$ netstat -atln | grep <Port>
$ netstat -st
$ lsof -i -n

###抓包:

  1. tcpdump 要用root权限去运行。
  2. tcpdump的参数：
    -D 表示查看网络适配器列表
    -X 表示要显示抓取包的内容
    -s 0 表示显示全部包的内容
    -i 3 表示抓取网络适配器列表编号为3的设备
    tcp port 8080 表示抓取经过8080端口的tcp包
$ tcpdump -X -s 0  -i 3 tcp port 8080

###alias

alias gnw='git log --color --graph --pretty=format:'\''%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr) %C(bold blue)<%an>%Creset'\'' --abbrev-commit --all'
alias l='ls -alFG'
alias ll='ls -AlFG'

###git:
1.clone a branch from git origin:

git clone -b develop git@192.168.1.21:project

2.create a new feature branch from this branch

git checkout -b feature-001 develop

3.finish

git commit --no-verify -m "..."
git checkout develop
git pull
git diff --name-status develop feature
git diff develop feature

4.merge back

git merge --no-ff  feature

5.push to origin

git push origin develop

6.delete local branch

git branch -d feature

7.delete remote branch

git push origin --delete feature

8.if the branch still in branch -a then remove such stale branches

git branch -d -r origin/feature