tr command in Unix Linux with examples - JohnHau/mis GitHub Wiki

Difficulty Level : Easy Last Updated : 19 Feb, 2021 The tr command in UNIX is a command line utility for translating or deleting characters. It supports a range of transformations including uppercase to lowercase, squeezing repeating characters, deleting specific characters and basic find and replace. It can be used with UNIX pipes to support more complex translation. tr stands for translate.

Syntax :

$ tr [OPTION] SET1 [SET2] Options

-c : complements the set of characters in string.i.e., operations apply to characters not in the given set -d : delete characters in the first set from the output. -s : replaces repeated characters listed in the set1 with single occurrence -t : truncates set1

Sample Commands

  1. How to convert lower case to upper case To convert from lower case to upper case the predefined sets in tr can be used.

$cat greekfile Output:

WELCOME TO GeeksforGeeks $cat greekfile | tr “[a-z]” “[A-Z]” Output:

WELCOME TO GEEKSFORGEEKS or

$cat geekfile | tr “[:lower:]” “[:upper:]” Output:

WELCOME TO GEEKSFORGEEKS 2. How to translate white-space to tabs The following command will translate all the white-space to tabs

$ echo "Welcome To GeeksforGeeks" | tr [:space:] '\t' Output:

Welcome To GeeksforGeeks
3. How to translate braces into parenthesis You can also translate from and to a file. In this example we will translate braces in a file with parenthesis.

$cat greekfile Output:

{WELCOME TO} GeeksforGeeks $ tr '{}' '()' newfile.txt Output:

(WELCOME TO) GeeksforGeeks The above command will read each character from “geekfile.txt”, translate if it is a brace, and write the output in “newfile.txt”.

  1. How to use squeeze repetition of characters using -s To squeeze repeat occurrences of characters specified in a set use the -s option. This removes repeated instances of a character. OR we can say that,you can convert multiple continuous spaces with a single space

$ echo "Welcome To GeeksforGeeks" | tr -s [:space:] ' ' Output:

Welcome To GeeksforGeeks 5. How to delete specified characters using -d option To delete specific characters use the -d option.This option deletes characters in the first set specified.

$ echo "Welcome To GeeksforGeeks" | tr -d 'w' Output:

elcome To GeeksforGeeks 6. To remove all the digits from the string, use

$ echo "my ID is 73535" | tr -d [:digit:] Output:

my ID is 7. How to complement the sets using -c option You can complement the SET1 using -c option. For example, to remove all characters except digits, you can use the following.

$ echo "my ID is 73535" | tr -cd [:digit:] Output:

73535