tr Command Examples

tr is an UNIX utility for translating, or deleting, or squeezing repeated characters. It will read from STDIN and write to STDOUT.

tr stands for translate.

$ tr [OPTION] SET1 [SET2]

1.Convert lower case to upper case

The following tr command is used to convert the lower case to upper case

$ tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ

The following command will also convert lower case to upper case

$ tr [:lower:] [:upper:]

You can also use ranges in tr. The following command uses ranges to convert lower to upper case.

$ tr a-z A-Z

2. 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.

$ tr '{}' '()' < inputfile > outputfile

The above command will read each character from “inputfile”, translate if it is a brace, and write the output in “outputfile”.


3. Translate white-space to tabs

The following command will translate all the white-space to tabs

$ echo "This is for testing" | tr [:space:] '\t'
This	is	for	testing

4. Squeeze repetition of characters using -s

In Example 3, we see how to translate space with tabs. But if there are two are more spaces present continuously, then the previous command will translate each spaces to a tab as follows.

$ echo "This   is   for testing" | tr [:space:] '\t'
This			is			for	testing

We can use -s option to squeeze the repetition of characters.

$ echo "This   is   for testing" | tr -s [:space:] '\t'
This	is	for	testing

Similarly you can convert multiple continuous spaces with a single space

$ echo "This  is  for testing" | tr -s [:space:] ' '
This is for testing

5. Delete specified characters using -d option

tr can also be used to remove particular characters using -d option.

$ echo "the geek stuff" | tr -d 't'
he geek suff

To remove all the digits from the string, use

$ echo "my username is 432234" | tr -d [:digit:]
my username is


6. 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 username is 432234" | tr -cd [:digit:]

7. Remove all non-printable character from a file

The following command can be used to remove all non-printable characters from a file.

$ tr -cd [:print:] < file.txt

8. Join all the lines in a file into a single line

The below command will translate all newlines into spaces and make the result as a single line.