bash string to uppercase code example

Example 1: 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 2: how to compare a character to uppercase in bash script

echo "enter a char"
read c

if [[ $c == [A-Z] ]];
then
    echo "upper"
elif [[ $c == [a-z] ]];
then
    echo "lower"
else 
    echo "Digit or special symbols!"
fi