shell script tips: bash and function

*** motivation ***
sh script does not have ${RANDOM} value which generates random value if used in bash script. Below is sample code explains how to use ${RANDOM} and define functions in bash scripts.

*** sample code (makeData.sh) ***

#!/bin/bash                                                                   

function create_db(){
  dbname=$1
  dbuser=$2
  dbpass=$3
  PGPASSWORD=${dbpass} dropdb -U ${dbuser} ${dbname}
  PGPASSWORD=${dbpass} createdb -U ${dbuser} ${dbname}
}

function create_tbl(){
  id=0
  dbname=$1
  dbuser=$2
  dbpass=$3
  dbtable=$4

  sql="CREATE TABLE ${dbtable} (id text, value int);"
  PGPASSWORD=${dbpass} psql -U ${dbuser} -d ${dbname} -c "${sql}"

  while [ ${id} -le 3 ]
  do
      id=`expr ${id} + 1`
      sql="INSERT INTO ${dbtable} VALUES (${id}, ${RANDOM});"
      PGPASSWORD=${dbpass} psql -U ${dbuser} -d ${dbname} -c "${sql}"
  done
}

function select_tbl(){
  dbname=$1
  dbuser=$2
  dbpass=$3
  dbtable=$4

  sql="SELECT * FROM ${dbtable};"
  PGPASSWORD=${dbpass} psql -U ${dbuser} -d ${dbname} -q -c "${sql}"
}

function main(){
  dbname=$1
  dbuser=$2
  dbpass=$3
  create_db ${dbname} ${dbuser} ${dbpass}

  sn=0
  prefix="table_"

  while [ ${sn} -le 23 ]
  do
      dbtable=${prefix}${sn}
      create_tbl ${dbname} ${dbuser} ${dbpass} ${dbtable}
      select_tbl ${dbname} ${dbuser} ${dbpass} ${dbtable}
      sn=`expr ${sn} + 1`
  done
}


# Program starts here!!!
if [ $# -ne 3 ]; then
  echo "usage: bash $0 dbname dbuser dbpass"
  exit
fi

main $1 $2 $3

*** output from above script ***

yaboo@maniac:~$ bash makeData.sh mydb test test 
id | value                                                                   
----+-------                                                                  
1  |   632                                                                   
2  |  5999                                                                   
3  |  3495                                                                   
4  |  3127                                                                   
(4 行)                                                                        
                                                                            
id | value                                                                   
----+-------                                                                  
1  | 29475                                                                   
2  |  7581                                                                   
3  | 17044                                                                   
4  | 12726                                                                   
(4 行)                                                                        
                                                                            
id | value                                                                   
----+-------                                                                  
1  | 13619                                                                   
2  | 25982                                                                   
3  | 21835                                                                   
4  | 23054                                                                   
(4 行)                                                                        
                                                                            
id | value                                                                   
----+-------                                                                  
1  |   726                                                                   
2  | 15405                                                                   
3  | 16549                                                                   
4  | 16405                                                                   
(4 行)                                                                        
                                                                            
id | value                                                                   
----+-------                                                                  
1  | 14362                                                                   
2  | 22030                                                                   
3  | 16364                                                                   
4  | 24379                                                                   
(4 行)                                                                        

...

id | value                                                                   
----+-------                                                                  
1  |  8468                                                                   
2  | 10413                                                                   
3  | 12345                                                                   
4  | 30637                                                                   
(4 行)                                                                        
                                                                            
id | value                                                                   
----+-------                                                                  
1  |  8372                                                                   
2  | 16466                                                                   
3  | 31683                                                                   
4  | 23073                                                                   
(4 行)                                                                        
                                                                            
yaboo@maniac:~$