Case Conversion

#!/bin/bash
name="Ada Lovelace"
echo "Uppercase: ${name^^}"
echo "Lowercase: ${name,,}"

#!/bin/bash
word="hello"
capitalized=${word^}
echo "Capitalized: $capitalized"
shouty="WORLD"
lowered_first=${shouty,}
echo "First letter lowered: $lowered_first"

#!/bin/bash
word="programming"
vowels_upper=${word^^[aeiou]}
echo "Vowels uppercased: $vowels_upper"

#!/bin/bash
name="Ada Lovelace"
upper=$(echo "$name" | tr '[:lower:]' '[:upper:]')
echo "Uppercase via tr: $upper"

1. Assuming case conversion parameter expansion (^^, ,,) works in old Bash versions; it was introduced in Bash 4.0, so scripts targeting very old Bash (like macOS's stock 3.2) need tr instead.
2. Confusing the single-character forms (^, ,) with the double-character forms (^^, ,,); the single form only affects the first character, the double form affects the entire string.
3. Forgetting these operators only work on plain variables in ${var^^}-style expansions, not directly on string literals -- you must store the text in a variable first.

• ${var^^} converts the entire string to uppercase; ${var,,} converts the entire string to lowercase.
• ${var^} uppercases only the first character; ${var,} lowercases only the first character.
• These are Bash 4.0+ features; older Bash (e.g. macOS's default 3.2) requires tr '[:lower:]' '[:upper:]' instead.
• You can also convert only characters matching a specific pattern, e.g. ${var^^[aeiou]} uppercases only vowels.