convert capital letters to lowercase in shell script code example

Example 1: bash transform uppercase to lowercase

Just use tr command to transform lowercase letters into uppercase as:
tr a-z A-Z < file.txt	#transforms letters into uppercase in a file
echo 'HELLO' | tr A-Z a-z	#Outputs: 'hello'

Example 2: bash how to convert text to lowercase or uppercase

# Basic syntax:
tolower(string)
toupper(string)

# Example usage:
awk '{print tolower($0)}' input_file
# This prints every row ($0) converted to lowercase

awk '{print toupper($3)}' input_file
# This would print the third field ($3) converted to uppercase

Example 3: convert capital letters to lowercase in shell script

x="HELLO"
echo $x  # HELLO

y=${x,,}
echo $y  # hello

z=${y^^}
echo $z  # HELLO