cli_training

test it with https://www.tutorialspoint.com/execute_bash_online.php

vim

• start of line - 0
• end of line - $
• next word - w
• previous word - b
• last line - G
• move to end of line and insert mode - A
• show line numbers - :set number
• syntax highlight - :syntax on
• set spaces amount for tab - :set tabstop=2
• set autoindent - :set autoindent
• check vimrc used - :echo $MYVIMRC
• select text - V and arrow down or up
• delete selected text - d
• clean all in vim: esc -> g -> g -> d -> G

cli

• permissions: 7(rwx),6(rw),5(rx),4(r),3(wx),2(w), 1(x), 0(no)

bash

• variable string(no spaces near equal sign)

myName="Name"

• const

declare -r NUM1=5

• arithmetics

num2=4
num3=$((NUM1+num2))
echo "5 + 4 = $num3"
echo $((5**2))
echo $((5%2))
rand=5
let rand+=4
echo "$rand"
echo "rand++ = $(( rand++ ))"
echo "++rand = $(( ++rand ))"

• float points

num7=1.2
num8=3.4

• python

num9=$(python -c "print $num7+$num8")
echo "$num9"

• cat multiline

cat<<END
This text 
prints on
many lines
END

• function

getDate(){
  date
  return 
}
getDate

• global and local variables

name="NameGlobal"
demLocal(){
  local name="nameLocal" #without local it will override name variable
  return
}
demLocal
echo "$name"

• function with arguments

getSum(){
  local num3=$1
  local num4=$2
  local sum=$((num3+num4))
  echo $sum
}
num1=5
num2=6
sum=$(getSum num1 num2)
echo "$sum"

• user input

read -p "What is your name?" name
echo $name

• condition

read -p "How old are you?" age
if[ $age -ge 16 ]
then
  echo "you can drive"
elif [ $age -eq 15]
then 
  echo "you can drive next year"
else
  echo "you can't drive next year"
fi

read -p "enter num: " num
if (( num == 10 )); then
  echo "Num is 10"
fi
if (( (( num % 2 )) == 0 )); then
  echo "even"
fi

if (( (( num > 2 )) && (( num == -1 ))  )); then
  echo "smth"
fi

• if string

if ["$str1"] ; then
    echo "str1 is not null"
fi
if [-z "$str1"] ; then
    echo "str1 has no value"
fi

if [ "$str1"=="$str2" ] ; then
    echo "eq"
fi

• if file exists (-x - executable, -r - readable, - f - reg file, -w - writable, -d - dir, -L - link, -S - socket, - G - owned by group, -O - user owned )

file1 = "file1.txt"
if [-e "$file1"]; then
  echo "$file1 exists"
fi

• regex

read -p "validate a date: " date
pat="^[0-9]{8}$"
if [[ $date =~ $pat ]]; then
  echo "date is ok"
fi

• remove spaces

num1=${num1//[[:blank:]]/}

• substitute in string

samp_string="the dog"
echo "{samp_string//dog/cat}"

• switch

case $num in
[0-5])
  echo "less than 5"
  ;;
6) 
  echo "more"
  ;;
[6-9]|1[0-8]
  echo "even more"
  ;;
*)
  echo "problem"
  ;;
esac  

• ternary operator

((age >=18?(can_vote=1):(can_vote=0)))

• parameter expansion

string="a rand string"
echo "String length : ${#string}"
echo "from second symbol till end ${string:2}"
echo "symbols ${string:2:7}"
echo "symbols after 'A ' ${string#*A }"

• while loop

num=1
while [$num -le 10]; do
  echo $num
  num=$((num+1))
  if(( ((num%2)) == 0)); then
    num=$((num + 1))
    continue
  fi
    if(( ((num%2)) == 1)); then
    break
  fi
done

• untill

until [$num -gt 10]; do
    echo $num
done

• another while reading file

while read avg rbis hrs; do 
 printf "Avg: ${avg}\nRBIs: ${rbis}\n HRs: ${hrs}\n"
done < barry_bonds.txt 

• arrays

nums=(1 2 -3 -4)
echo "${nums[0]}"
for i in ${nums[*]}; do
  echo $i
done
for i in ${nums[@]}; do
  echo $i
done
echo "Array length: ${#nums[@]}"
echo "Index 3 length: ${#nums[3]}"
sorted_nums=($(for i in "${nums[@]}"; do
  echo $i;
done | sort))
for i in ${sorted_nums[*]}; do
  echo $i
done

echo "1st arg: $1"
sum=0
//$# - number of args
while [[ $# -gt 0 ]]; do
  num=$1
  sum=$((sum+num))
  shift// moves argument two into position 1
done