tr text transformation

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# Convert lowercase to uppercase
echo "hello world" | tr 'a-z' 'A-Z'
# Output: HELLO WORLD

# Convert uppercase to lowercase
echo "HELLO WORLD" | tr 'A-Z' 'a-z'
# Output: hello world

# Replace spaces with underscores
echo "hello world" | tr ' ' '_'
# Output: hello_world

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# Delete specific characters
echo "hello123world" | tr -d '0-9'
# Output: helloworld

# Delete spaces
echo "h e l l o" | tr -d ' '
# Output: hello

# Delete newlines
cat file.txt | tr -d '\n'

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# Squeeze multiple spaces to single space
echo "hello    world" | tr -s ' '
# Output: hello world

# Squeeze repeated newlines
cat file.txt | tr -s '\n'

# Remove blank lines
cat file.txt | tr -s '\n' | grep .

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# Convert Windows line endings to Unix
tr -d '\r' < windows.txt > unix.txt

# Remove all non-alphanumeric characters
echo "hello@world!123" | tr -cd '[:alnum:]'
# Output: helloworld123

# Replace multiple characters at once
echo "hello-world_test" | tr '_-' ' '
# Output: hello world test

# Convert CSV to TSV
cat file.csv | tr ',' '\t' > file.tsv

# ROT13 encoding
echo "hello" | tr 'A-Za-z' 'N-ZA-Mn-za-m'

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# Using POSIX character classes
tr '[:lower:]' '[:upper:]'  # Lowercase to uppercase
tr -d '[:digit:]'           # Delete all digits
tr -d '[:punct:]'           # Delete punctuation
tr -d '[:space:]'           # Delete all whitespace