Linux Bash Script

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今天我想分享如何用linux shell script 語法。
我們需要加這個在script裡面，然後檔案改成.sh

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#! /bin/bash
  • How to execute script

    chmod 777 myscript.sh
    ./myscript.sh

1. variable

define variable

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text1=Hello
name=CC
echo $text1 $name

output:

Hello CC

read and echo variable

read variable

read a

read vairable without skip new line:

read -p “Your Options: “ option

echo without new line

echo -n “message”

example:

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echo "======================IPERF==================="
echo "1) "
echo "2) "
echo "q) "
echo "============================="
echo -n "Choice:"
read choice

expression

var=$((3+9))
echo $var

output:
　12

  • example 
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    echo "Enter a numner"
    read a
    echo "Enter a numner"
    read b
    echo $sum
    echo $a $b
    sum=$((a+b))

2. condition

if elif else

Syntax

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if [[ condition ]]
then
	statement
elif [[ condition ]]; then
	statement 
else
	do this by default
fi

check file empty

if [[ -z "$tftp_dir" ]]

example

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read x
read y

if [ $x -gt $y ]
then
echo X is greater than Y
elif [ $x -lt $y ]
then
echo X is less than Y
elif [ $x -eq $y ]
then
echo X is equal to Y
fi

3. Loop

for loop

loop number

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for i in {1..5}
do
    echo $i
done

Looping with strings

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for X in hello world 
do
	echo $X
done

while loop

adding 1 ~100

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#!/bin/bash
i=1
while [[ $i -le 10 ]] ; do
   echo "$i"
  (( i += 1 ))
done

get arguments for scripts

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#!/bin/bash
for x in $@
do
    echo "Entered arg is $x"
done

./filename value1 value2 value3