If/for/while/case case case of shell

Often forget Shell grammar , Record here ：

if

#  Judge that the incoming parameter must be greater than 1
if [ $# -lt 1 ]; then
    echo "[WARNNING]  Please enter the file you want to sync ！！"
    exit 0;
fi


$#   Indicates the number of parameters 
$0   Represents the file name of the current script 
$1   Represents the first parameter 
$2   Represents the second parameter 
$*   Represents all parameters passed to a script or function 
$$   At present Shell process ID. about  Shell  Script , It's the process of these scripts ID

for

for host in slave1 slave2
do
  echo ====================  $host  ====================
done

case

#! /bin/bash
case $1 in
"start"){
    
    for i in master slave1 slave2
    do
        echo " -------- start-up  $i Kafka-------"
        ssh $i "/opt/module/kafka/bin/kafka-server-start.sh -daemon /opt/module/kafka/config/server.properties"
    done
};;
"stop"){
    
    for i in master slave1 slave2
    do
        echo " -------- stop it  $i Kafka-------"
        ssh $i "/opt/module/kafka/bin/kafka-server-stop.sh stop"
    done
};;
esac

while

Calculation 1-100 And

#!/bin/bash
i=1
sum=0
while [ $i -le 100 ]
do
  let sum=sum+$i
  let i++
done

echo $sum

Case study

1. Sync files 、 Script for folder

#!/bin/bash

#  Judge that the incoming parameter must be greater than 1
if [ $# -lt 1 ]; then
    echo "[WARNNING]  Please enter the file you want to sync ！！"
    exit 0;
fi

#  Define the absolute path of the incoming parameter 
absdir=$(cd -P $(dirname $1); pwd)

#  Perform the transfer 
#2.  Traverse all machines in the cluster 
for host in slave1 slave2
do
  echo ====================  $host  ====================
  #3.  Traverse all directories , Send... One by one 
  for file in [email protected]
  do
    #4  Judge whether the file exists 
    if [ -e $file ]; then
      #5.  Get parent directory 
      pdir=$(cd -P $(dirname $file); pwd)
      #6.  Get the name of the current file 
      fname=$(basename $file)
      ssh $host "mkdir -p $pdir"
      rsync -av $pdir/$fname $host:$pdir  # -a  Indicates transmission in archive mode  -v  Represents the output details 
    else
      echo $file does not exists!
    fi
  done
done

#  How to use ？
# 1.  Add executable permissions to the script 
$ chmod +x /zlp/scripts/bin/xsync

# 2. Add your own script to the environment variable 
$ vim /etc/profile.d/my_profile.sh
	export  PATH=$PATH:/zlp/scripts/bin
	
# 3. distribution  /scripts  Folder 
$  xsync   /scripts/