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tr command in Unix/Linux with examples

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  • Difficulty Level : Easy
  • Last Updated : 01 Dec, 2022
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The tr command is a UNIX 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 characters to upper case. To convert characters from lower case to upper case, you can either specify a range of characters or use the predefined character classes. 

$ cat greekfile

Output:

WELCOME TO 
GeeksforGeeks
$ cat greekfile | tr [a-z] [A-Z]

Output:

WELCOME TO
GEEKSFORGEEKS

or

$ cat greekfile | tr [:lower:] [:upper:]

Output:

WELCOME TO
GEEKSFORGEEKS

Alternatively, you can provide input for the tr command using redirection:

tr [:lower:] [:upper:] <greekfile

Output:

WELCOME TO
GEEKSFORGEEKS

2. How to translate white-space characters to tabs. The following command translates all the white-space characters to tabs

$ echo "Welcome To GeeksforGeeks" | tr [:space:] "\t"

Output:

Welcome    To    GeeksforGeeks

In the previous example we can also use redirection to provide intput for tr. Although this time we will use a here string for that:

tr [:space:] "\t" <<< "Welcome To GeeksforGeeks"

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 "{}" "()" <greekfile >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 to “newfile.txt”.

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

$ echo "Welcome    To    GeeksforGeeks" | tr -s " "

Output:

Welcome To GeeksforGeeks

And again, accomplish the same task but using a string here:

tr -s " " <<< "Welcome    To    GeeksforGeeks"

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

Or equivalently use:

tr -d W <<< "Welcome to GeeksforGeeks"

Output:

elcome To GeeksforGeeks

6. To remove all the digits from the string, you can use

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

or

$ tr -d [:digit:] <<< "my ID is 73535"

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:]

or

$ tr -cd [:digit:] <<< "my ID is 73535"

Output:

73535

This article is contributed by Shivani Ghughtyal. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

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