for-loop-list.sh

#!/bin/bash

for each in one two three; do
    echo $each
done

servers=( 
gtx{0..3}-ev.zur
gtx4-ev.zur
)

# print all element from array 
for each_node in "${servers[@]}" ; do
    echo "$each_node"
done

# print elements with indexes
for (( index=0; index<${#servers[@]}; index++ )); do
    echo $index"   "${servers[$i]}
done 

BRANDS_LIST=($(ls *.brands_s3))
BRANDS_LIST=("one.brands_s3" "two.brands_s3" "three.brands_s3")
for each_value in "${BRANDS_LIST[@]}"; do    
    echo $each_value
done

# one line print ( no semicolon after "do" ), inline while
printf 'one\n two\n three\n' | while read each_value;do echo $each_value;done
find . -name "*.json" | while read each_file; do cat "$each_file" > "${each_file}".txt; done

# the same but shorter
# for each_node in gtx{0..4}-ev.zur ; do

# loop through values with spaces
IFS=$'\n' # it is necessary for non-manual input, for new line for loop line
# !!! warning !!! for file reading must be new line at the end 
for each_string in "one" "two" "three four five"
do
   echo $each_string
done


# example of walking through list of environment variables, variable of variable, variable by name
for each_val in "MYSQL_ROOT_PASSWORD" "MYSQL_USER" "MYSQL_PASSWORD"
do
    # declare "current_variable=$each_val"
    # if [ -z ${!current_variable} ]; then
    if [ -z $each_val ]
        echo "file .env should contains $each_val"
        exit 1
    fi
done


# for array 
my_list=("one" "two" "three")
for each_string in ${my_list[@]}; do
   echo $each_string
done

# for loop elements with space
IFS=$'\n' # shell variables: https://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html#tag_02_05_03
# IFS=' '
# echo $IFS | hexdump
values='hello from
our world
not from another'
for each_value in $values; do
    echo $each_value
done

# for dictionary/maps/associated arrays
declare -A firms
firms[microsoft]='soft'
firms[bmw]='auto'
firms[lidl]='food'

# print key-value 
for key in "${!firms[@]}"; do
    echo "  $key: ${firms[$key]}"
done

# Collect all keys into a standard array
firm_keys=("${!firms[@]}")
# Print all keys
echo "Keys in associative array 'firms':"
for key in "${firm_keys[@]}"; do
    echo "$key"
done