Bash tr Command - Translate or Delete Characters

Using the tr Command

The tr (translate) command replaces characters with other characters. It can also delete characters, or squeeze repeated ones into one.

tr only reads from input, so you send text to it with a pipe or with <.

Replace Characters

Give tr two sets of characters. Each character in the first set is replaced by the character in the same place in the second set:

echo "hello" | tr "el" "ip"
hippo

Here, e became i and every l became p.

Change Upper and Lower Case

Use ranges like a-z and A-Z to change the case of text:

echo "Hello World" | tr "a-z" "A-Z"
HELLO WORLD

You can also use the named classes [:lower:] and [:upper:]:

echo "Hello World" | tr "[:upper:]" "[:lower:]"
hello world

Delete Characters (-d)

Use -d to delete every character in the set:

echo "Order 123 is ready" | tr -d "0-9"
Order  is ready

Squeeze Repeated Characters (-s)

Use -s to replace a run of the same character with just one:

echo "too    many     spaces" | tr -s " "
too many spaces

One Word per Line

A common trick is to replace spaces with new lines (\n), to put each word on its own line:

echo "red green blue" | tr " " "\n"
red
green
blue

Options Overview

• tr SET1 SET2: Replace characters in SET1 with those in SET2
• -d: Delete characters
• -s: Squeeze repeated characters into one
• -c: Use every character that is NOT in the set