How to read a .properties file which contains keys that have a period character using Shell script

I use simple grep inside function in bash script to receive properties from .properties file.

This properties file I use in two places - to setup dev environment and as application parameters.

I believe that grep may work slow in big loops but it solves my needs when I want to prepare dev environment.

Hope, someone will find this useful.

Example:

File: setup.sh

#!/bin/bash

ENV=${1:-dev}

function prop {
    grep "${1}" env/${ENV}.properties|cut -d'=' -f2
}

docker create \
    --name=myapp-storage \
    -p $(prop 'app.storage.address'):$(prop 'app.storage.port'):9000 \
    -h $(prop 'app.storage.host') \
    -e STORAGE_ACCESS_KEY="$(prop 'app.storage.access-key')" \
    -e STORAGE_SECRET_KEY="$(prop 'app.storage.secret-key')" \
    -e STORAGE_BUCKET="$(prop 'app.storage.bucket')" \
    -v "$(prop 'app.data-path')/storage":/app/storage \
    myapp-storage:latest

docker create \
    --name=myapp-database \
    -p "$(prop 'app.database.address')":"$(prop 'app.database.port')":5432 \
    -h "$(prop 'app.database.host')" \
    -e POSTGRES_USER="$(prop 'app.database.user')" \
    -e POSTGRES_PASSWORD="$(prop 'app.database.pass')" \
    -e POSTGRES_DB="$(prop 'app.database.main')" \
    -e PGDATA="/app/database" \
    -v "$(prop 'app.data-path')/database":/app/database \
    postgres:9.5

File: env/dev.properties

app.data-path=/apps/myapp/

#==========================================================
# Server properties
#==========================================================
app.server.address=127.0.0.70
app.server.host=dev.myapp.com
app.server.port=8080

#==========================================================
# Backend properties
#==========================================================
app.backend.address=127.0.0.70
app.backend.host=dev.myapp.com
app.backend.port=8081
app.backend.maximum.threads=5

#==========================================================
# Database properties
#==========================================================
app.database.address=127.0.0.70
app.database.host=database.myapp.com
app.database.port=5432
app.database.user=dev-user-name
app.database.pass=dev-password
app.database.main=dev-database

#==========================================================
# Storage properties
#==========================================================
app.storage.address=127.0.0.70
app.storage.host=storage.myapp.com
app.storage.port=4569
app.storage.endpoint=http://storage.myapp.com:4569
app.storage.access-key=dev-access-key
app.storage.secret-key=dev-secret-key
app.storage.region=us-east-1
app.storage.bucket=dev-bucket

Usage:

./setup.sh dev

As (Bourne) shell variables cannot contain dots you can replace them by underscores. Read every line, translate . in the key to _ and evaluate.

#/bin/sh

file="./app.properties"

if [ -f "$file" ]
then
  echo "$file found."

  while IFS='=' read -r key value
  do
    key=$(echo $key | tr '.' '_')
    eval ${key}=\${value}
  done < "$file"

  echo "User Id       = " ${db_uat_user}
  echo "user password = " ${db_uat_passwd}
else
  echo "$file not found."
fi

Note that the above only translates . to _, if you have a more complex format you may want to use additional translations. I recently had to parse a full Ant properties file with lots of nasty characters, and there I had to use:

key=$(echo $key | tr .-/ _ | tr -cd 'A-Za-z0-9_')

Since variable names in the BASH shell cannot contain a dot or space it is better to use an associative array in BASH like this:

#!/bin/bash

# declare an associative array
declare -A arr

# read file line by line and populate the array. Field separator is "="
while IFS='=' read -r k v; do
   arr["$k"]="$v"
done < app.properties

Testing:

Use declare -p to show the result:

  > declare -p arr  

        declare -A arr='([db.uat.passwd]="secret" [db.uat.user]="saple user" )'

For a very high performance, and BASH 3.0 compatible solution:

file: loadProps.sh

function loadProperties() {
  local fileName=$1
  local prefixKey=$2

  if [ ! -f "${fileName}" ]; then
    echo "${fileName} not found!"
    return 1
  fi

  while IFS='=' read -r origKey value; do
    local key=${origKey}
    key=${key//[!a-zA-Z0-9_]/_} 
    if [[ "${origKey}" == "#"*   ]]; then
      local ignoreComments
    elif [ -z "${key}" ]; then
      local emptyLine
    else
      if [[ "${prefixKey}${key}" =~ ^[0-9].* ]]; then
        key=_${key}
      fi
      eval ${prefixKey}${key}=\${value}
    fi
  done < <(grep "" ${fileName})
}

The other solutions provided here are great and elegant, but

@fork2execve: slow when dealing with large properties files
@Nicolai: slow when reading lots of properties
@anubhava: require BASH 4.0 (for the array)

I needed something working on bash 3, dealing with properties files of ~1k entries, reading ~200 properties, and whole script called MANY times.

this function also deals with

empty lines
commented code
duplicated entries (last one wins)
normalize property names
last line without a proper new line

Testing

file: my.properties

a=value
a=override value
b=what about `!@#$%^&*()_+[]\?
c=${a} no expansion
d=another = (equal sign)
e=     5 spaces front and back     
f=
#g=commented out
#ignore new line below

.@a%^=who named this???
a1=A-ONE
1a=ONE-A
X=lastLine with no new line!

test script

. loadProps.sh

loadProperties my.properties PROP_
echo "a='${PROP_a}'"
echo "b='${PROP_b}'"
echo "c='${PROP_c}'"
echo "d='${PROP_d}'"
echo "e='${PROP_e}'"
echo "f='${PROP_f}'"
echo "g='${PROP_g}'"
echo ".@a%^='${PROP___a__}'"
echo "a1='${PROP_a1}'"
echo "1a='${PROP_1a}'"
echo "X='${PROP_X}'"

loadProperties my.properties
echo "a='${a}'"
echo "1a='${_1a}'"

output

a='override value'
b='what about `!@#$%^&*()_+[]\?'
c='${a} no expansion'
d='another = (equal sign)'
e='     5 spaces front and back     '
f=''
g=''
.@a%^='who named this???'
a1='A-ONE'
1a='ONE-A'
X='lastLine with no new line!'
a='override value'
1a='ONE-A'

Performance Test

. loadProps.sh

function fork2execve() {
  while IFS='=' read -r key value; do
    key=$(echo $key | tr .-/ _ | tr -cd 'A-Za-z0-9_')
    eval ${key}=\${value}
  done < "$1"
}

function prop {
  grep '^\s*'"$2"'=' "$1" | cut -d'=' -f2-
}

function Nicolai() {
  for i in $(seq 1 $2); do 
    prop0000=$(prop $1 "property_0000")
  done
}

function perfCase() {
  echo "perfCase $1, $2, $3"
  time for i in $(seq 1 1); do 
    eval $1 $2 $3
  done
}

function perf() {
  perfCase $1 0001.properties $2
  perfCase $1 0010.properties $2
  perfCase $1 0100.properties $2
  perfCase $1 1000.properties $2
}

perf "loadProperties"
perf "fork2execve"
perf "Nicolai" 1
perf "Nicolai" 10
perf "Nicolai" 100

with 4 NNNN.properties files with entries such as

property_0000=value_0000
property_0001=value_0001
...
property_NNNN=value_NNNN

resulted with

function   , file,   #,     real,    user,     sys
loadPropert, 0001,    ,    0.058,   0.002,   0.005
loadPropert, 0010,    ,    0.032,   0.003,   0.005
loadPropert, 0100,    ,    0.041,   0.013,   0.006
loadPropert, 1000,    ,    0.140,   0.106,   0.013

fork2execve, 0001,    ,    0.053,   0.003,   0.007
fork2execve, 0010,    ,    0.211,   0.021,   0.051
fork2execve, 0100,    ,    2.146,   0.214,   0.531
fork2execve, 1000,    ,   21.375,   2.151,   5.312

Nicolai    , 0001,   1,    0.048,   0.003,   0.009
Nicolai    , 0010,   1,    0.047,   0.003,   0.009
Nicolai    , 0100,   1,    0.044,   0.003,   0.010
Nicolai    , 1000,   1,    0.044,   0.004,   0.009

Nicolai    , 0001,  10,    0.240,   0.020,   0.056
Nicolai    , 0010,  10,    0.263,   0.021,   0.059
Nicolai    , 0100,  10,    0.272,   0.023,   0.062
Nicolai    , 1000,  10,    0.295,   0.027,   0.059

Nicolai    , 0001, 100,    2.218,   0.189,   0.528
Nicolai    , 0010, 100,    2.213,   0.193,   0.537
Nicolai    , 0100, 100,    2.247,   0.196,   0.543
Nicolai    , 1000, 100,    2.323,   0.253,   0.534

@fork2x

I have tried like this .Please review and update me whether it is right approach or not.

#/bin/sh
function pause(){
   read -p "$*"
}

file="./apptest.properties"


if [ -f "$file" ]
then
    echo "$file found."

dbUser=`sed '/^\#/d' $file | grep 'db.uat.user'  | tail -n 1 | cut -d "=" -f2- | sed 's/^[[:space:]]*//;s/[[:space:]]*$//'`
dbPass=`sed '/^\#/d' $file | grep 'db.uat.passwd'  | tail -n 1 | cut -d "=" -f2- | sed 's/^[[:space:]]*//;s/[[:space:]]*$//'`

echo database user = $dbUser
echo database pass = $dbPass

else
    echo "$file not found."
fi

How to read a .properties file which contains keys that have a period character using Shell script

Testing

Performance Test

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