Linux reference sheet

User info:

whoami
hostname
su username
sudo date
sudo su - switch to the superuser account

Command parameter format:

command -p 10
command --parameter=10

ls -a      single character parameter name
ls --all     full parameter name

Hotkey:

ctrl + A  //光标跳到一行命令的开头。Home 键有相同的效果；
ctrl + E   //光标跳到一行命令的结尾。End 键有相同的效果；

Command execution outside of $PATH:

/full/path/to/command
./command-in-this-dir

Chmod:

chmod ugoa+-=rwx file

vi:

x - delete a character
dd - delete a line
yy - copy a line
D - delete from current position till line end
p - paste
/ - search forward
? - search hehind
u - undo
:s/旧字符串/新字符串/g

find a file:

find /var/log -name "syslog"
sudo updatedb
locate filename | grep `pwd`

System monitoring:

du -h  \\disk usage

Text manipulation:

grep -i #ignore case
grep -v #invert match
cut -d delimiter
cut -f N dispay the nth field
cut -d'  ' -f2
grep bob /etc/passwd | cut -d: -f1,5 | sort | tr ":" " "
uniq test.txt  - only remove consecutive lines

SCP, RSYNC and SFTP:

scp username@from_host:file.txt /local/directory/
scp file.txt username@to_host:/remote/directory/

sftp tecmint@27.48.137.6
sftp> put local.profile
Uploading local.profile to /tecmint/local.profile
sftp> get SettlementReport_1-10th.xls
Fetching /tecmint/SettlementReport_1-10th.xls to SettlementReport_1-10th.xls

rsync -arv --delete Images/ oscar@89.231.45.67:backups/

Tar:

tar -cvf sorting.tar sorting/       - create
tar -xvf sorting.tar          -extract

tar -zcvf
tar -zxvf         -  add gunzip 
zcat，zmore，zless, zgrep      -  add gunzip

Link:
ln hard link to same inode

ln -s soft link creates a new inode pointing to old filename

0 stdin, 1 stdout, 2 stderr:

cat not_exist_file.csv > results.txt 2> errors.log
cat not_exist_file.csv > results.txt 2>&1
cat not_exist_file.csv >> results.txt 2>&1    - append

nohup continues after user has logged out:

nohup cp node-v10.15.3.tar.gz node-v10.15.3-copy.tar.gz &

&&：&& 号前的命令执行成功，才会执行后面的命令。
||：|| 号前的命令执行失败，才会执行后面的命令。
分号：不论分号前的命令执行成功与否，都执行分号后的命令。前后命令之间没有相关性。

ifconfig
en: ethernet
lo: loopback
wlan: wireless network

' '  ignore special chars
" "  takes $, `, and \
` ` execute

alias var="var1"
export var="var1"

#!/bin/bash

message='Hello World'
echo "The message is $message"

#!/bin/bash

message=`pwd`
echo "You are in the directory $message"

在 Bash 中，所有的变量都是字符串

env - show environment variable

./variable.sh 参数1 参数2 参数3 ...
$# ：包含参数的数目。
$0 ：包含被运行的脚本的名称（我们的示例中就是 variable.sh ）。
$1：包含第一个参数。
$2：包含第二个参数。

#!/bin/bash

array=('value0' 'value1' 'value2')
array[5]='value5'
echo ${array[1]}

if [ 条件测试 ]; then
做这个
fi

if [ 条件测试 1 ]
then
做事情 1
elif [ 条件测试 2 ]
then
做事情 2
elif [ 条件测试 3 ]
then
做事情 3
else
做其他事情
fi

#!/bin/bash

if [ $# -ge 1 ] && [ $1 = 'love' ]
then
    echo "Great !"
    echo "You know the password"
else
    echo "You do not know the password"
fi

#!/bin/bash

read -p 'Enter a file : ' file

if [ ! -e $file ]
then
    echo "$file does not exist"
else
    echo "$file exists"
fi

#!/bin/bash

for animal in 'dog' 'cat' 'pig'
do
    echo "Animal being analyzed : $animal" 
done
 
#!/bin/bash

for file in `ls *.sh`
do
    cp $file $file-copy
done

#!/bin/bash

while [ -z $response ] || [ $response != 'yes' ]
do
    read -p 'Say yes : ' response
done

#!/bin/bash

# Verification of parameter（验证参数）
# If no parameter, use a default value（如果没有给出参数，那么用默认值 gallery.html ）
if [ -z $1 ]
then
    output='gallery.html'
else
    output=$1
fi

# Preparation of files and folders（准备文件和目录）
echo '' > $output

if [ ! -e thumbnails ]
then
    mkdir thumbnails
fi

# Beginning of HTML（HTML 文件的开头）
echo '<!DOCTYPE html>
<html>
  <head>
    <title>My Gallery</title>
  </head>
  <body>
    <p>' >> $output

# Generation of thumbnails and the HTML web page（生成图片的缩略图和 HTML 的页面主体）
for image in `ls *.jpg *.png *.jpeg *.gif 2>/dev/null`
do
    convert $image -thumbnail '200x200>' thumbnails/$image
    echo '      <a href="'$image'"><img src="thumbnails/'$image'" alt=""/></a>' >> $output
done

# End of HTML（HTML 文件的结尾）
echo '    </p>
  </body>
</html>' >> $output

#!/bin/bash

# Verification of parameter
# 确认参数
if [ -z $1 ]
then
    echo "Please enter the file of dictionary !"
    exit
fi

# Verification of file existence
# 确认文件存在
if [ ! -e $1 ]
then
    echo "Please make sure that the file of dictionary exists !"
    exit
fi

# Definition of function
# 函数定义
statistics () {
  for char in {a..z}
  do
    echo "$char - `grep -io "$char" $1 | wc -l`" | tr /a-z/ /A-Z/ >> tmp.txt
  done
  sort -rn -k 2 -t - tmp.txt
  rm tmp.txt
}

# Use of function
# 函数使用
statistics $1

其中 -r 和 -n 参数我们比较熟悉，-n 参数用于对数字排序，-r 参数用于倒序排列。
-k 参数用于指定根据哪几列进行排序，这里用 -k 2 表示根据第 2 列来排序。
-t 参数用于指定列和列之间用什么作为分隔符，这里用 -t - 表示分隔符是 - 。

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Linux reference sheet

Javascript 5 - DOM