tr - Translate characters

Synopsis

tr [-cs] string1 string2

tr [-c] -d string1

tr [-c] -s string1

tr [-c] -ds string1 string2

Description

The tr utility copies the standard input to the standard output with substitution or deletion of selected characters.

In the first synopsis form, the characters in string1 are translated into the characters in string2 where the first character in string1 is translated into the first character in string2 and so on. If string1 is longer than string2, the last character found in string2 is duplicated until string1 is exhausted.

In the second synopsis form, the characters in string1 are deleted from the input.

In the third synopsis form, the characters in string1 are compressed as described for the -s option below.

In the fourth synopsis form, the characters in string1 are deleted from the input, and the characters in string2 are compressed as described for the -s option below.

The following conventions can be used in string1 and string2 to specify sets of characters. Any character not described by one of the following conventions represents itself.

nnn
A backslash (\) followed by 1, 2 or 3 octal digits represents a character with that encoded value.
char
To follow an octal sequence with a digit as a character, left zero-pad the octal sequence to the full 3 octal digits. A backslash (\) followed by certain special characters maps to special values. The special characters and their values are:
  • a - alert character
  • b - backspace
  • f - form-feed
  • n - newline
  • r - carriage return
  • t - tab
  • v - vertical tab
  • A backslash (\) followed by any other character maps to that character.
c-c
Represents the range of characters between the range endpoints, inclusively.
[:class:]
Represents all characters belonging to the defined character class. These are the class names:
  • alnum - alphanumeric characters
  • alpha - alphabetic characters
  • cntrl - control characters
  • digit - numeric characters
  • graph - graphic characters
  • lower - lower-case alphabetic characters
  • print - printable characters
  • punct - punctuation characters
  • space - space characters
  • upper - upper-case characters
  • xdigit - hexadecimal characters
Note: With the exception of the upper and lower classes, characters in the classes are in unspecified order. In the upper and lower classes, characters are entered in ascending order.

Options

-c
Complement the set of characters in string1, that is -c ab includes every character except for "a" and "b".
-d
Delete characters from the input.
-s
Squeeze multiple occurrences of the characters listed in the last operand (either string1 or string2) in the input into a single instance of the character. This occurs after all deletion and translation is completed.

Exit status

  • 0 on success
  • >0 if an error occurs.

Examples

  1. Create a list of the words in file1, one per line, where a word is taken to be a maximal string of letters. 
    
tr -cs '[:alpha:]' 'n' < file1
  2. Translate the contents of file1 to upper-case. 
    
tr '[:lower:]' '[:upper:]' < file1
tr 'a-z' 'A-Z' < file1
  3. Remove the non-printable characters from file1. 
    
tr -cd '[:print:]' < file1