#!/bin/bash
  
  tmp=0
  echo "input the three number"
  read -p "1:" a
  read -p "2:" b
  read -p "3:" c
  if [ $a -gt $b ]
  then
          tmp=$a
          a=$b
          b=$tmp
  fi
  if [ $a -gt $c ]
  then
          tmp=$a
          a=$c
          c=$tmp
  fi
  if [ $b -gt $c ]
  then
          tmp=$b
          b=$c
          c=$tmp
  fi
  echo "the sorted number is : $a $b $c"

自测：
Loong:/home/yee# sh -x compare.sh 
+ tmp=0
+ echo ‘input the three number‘
input the three number
+ read -p 1: a
1:23
+ read -p 2: b
2:43
+ read -p 3: c
3:35
+ ‘[‘ 23 -gt 43 ‘]‘
+ ‘[‘ 23 -gt 35 ‘]‘
+ ‘[‘ 43 -gt 35 ‘]‘
+ tmp=43
+ b=35
+ c=43
+ echo ‘the sorted number is : 23 35 43‘
the sorted number is : 23 35 43
Loong:/home/yee# sh -x compare.sh 
+ tmp=0
+ echo ‘input the three number‘
input the three number
+ read -p 1: a
1:12
+ read -p 2: b
2:13
+ read -p 3: c
3:16
+ ‘[‘ 12 -gt 13 ‘]‘
+ ‘[‘ 12 -gt 16 ‘]‘
+ ‘[‘ 13 -gt 16 ‘]‘
+ echo ‘the sorted number is : 12 13 16‘
the sorted number is : 12 13 16
Loong:/home/yee# sh -x compare.sh 
+ tmp=0
+ echo ‘input the three number‘
input the three number
+ read -p 1: a
1:54
+ read -p 2: b
2:43
+ read -p 3: c
3:32
+ ‘[‘ 54 -gt 43 ‘]‘
+ tmp=54
+ a=43
+ b=54
+ ‘[‘ 43 -gt 32 ‘]‘
+ tmp=43
+ a=32
+ c=43
+ ‘[‘ 54 -gt 43 ‘]‘
+ tmp=54
+ b=43
+ c=54
+ echo ‘the sorted number is : 32 43 54‘
the sorted number is : 32 43 54