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contra-variance from typing import Callable class Food: ... class Meat(Food): ... class Animal: def eat(self, food: Food): ... class Dog(Animal): def 阅读全文
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keyword must be strings 阅读全文
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C int arr[5]; brackets must follow the identifier, definition of variable with array type needs an explicit size of an initializer 阅读全文
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slice, map即使为nil打印格式和空元素的情况一样, chan,func,interface,pointer为nil时,打印<nil> 当chan,func,pointer赋值后,都打印地址, interface赋值后,永远打印其dynamic value的格式 package main i 阅读全文
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Java arr本质是一个数组,可直接传数组,引用类型,可能为null JavaScript Function length rest parameter Go 阅读全文
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C Java == 基本数据类型时, two operands类型不同时, 必须可以进行自动类型转换, e.g. byte & char => int, 不能进行自动类型转换(boolean & char)则编译失败, == 不能比较基本类型和引用类型, 基本数据类型只有boolean不能与其他7个 阅读全文
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man [options...] [SECTION] PAGE... -l --local-file interpret PAGE arguments as local filenames man -l /usr/share/man/man1/ls.1.gz 阅读全文
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env in jenkins controller Jenkins dynamic slave agent Pod Template in Jenkins UI Example from git pipeline { agent { kubernetes { cloud 'kubernetes' d 阅读全文
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$@ "$@" $* "$*" a.sh echo "$@" echo $@ echo "$*" echo $* b.sh "$@" b.sh $@ b.sh "$*" b.sh $* b.sh echo $# for param; do echo "param = $param" done 阅读全文
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C goto Must be defined within a function Each label in one function must have a unique name. It cannot be a reserved C keyword C has a separate namesp 阅读全文
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The switch expression has an additional lambda-like syntax and it can be used not only as a statement, but also as an expression that evaluates to a s 阅读全文
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In Java, C, $ is valid In Go, Python, $ is invalid 阅读全文
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def get_public_ip(): from urllib.request import urlopen import re as r d = urlopen('http://checkip.dyndns.com').read() return r.compile(r'(\d+\.\d+\.\ 阅读全文
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< file cat dd iflag=nonblock status=none if=file printf '%s' "$(< file)" cp file /dev/stdout awk '{print}' file sed '' file 阅读全文
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groupadd & useradd They all have --root CHROOT_DIR AND --prefix PREFIX_DIR 阅读全文
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HISTCONTROL variable is a colon-separated list of values controlling how commands are saved in the history list. HISTCONTROL=ignoredups It causes line 阅读全文
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ssh-keyscan - gather ssh public keys from servers /etc/ssh/ssh_config => HostKey 有系统内置的key options -c Request certificates from target hosts instead o 阅读全文
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escape inputs 阅读全文
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Disable all auth (in case of Security Realm wrong configuration) Go to $JENKINS_HOME, modify config.xml REST API # acquire crumb curl -fsSL -XGET -uje 阅读全文
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apiVersion: v1 Kind: pod apiVersion: v1 kind: Pod metadata: annotations: kubeadm.kubernetes.io/kube-apiserver.advertise-address.endpoint: 192.168.8.11 阅读全文