utility copies the standard input to
the standard output with substitution or deletion of selected characters.
The options are as follows:
- Complements the set of characters in
string1; for instance,
“-C ab” includes every character except for
‘a’ and ‘b’.
- The same as
-d option causes characters to be
deleted from the input.
-s option squeezes multiple
occurrences of the characters listed in the last operand (either
string2) in the input into a single
instance of the character. This occurs after all deletion and translation
In the first synopsis form, the characters in
are translated into the characters in
where the first character in
is translated into the first
character in string2
and so on. If
is longer than
, the last character found in
is duplicated until
In the second synopsis form, the characters in
are deleted from the input.
In the third synopsis form, the characters in
are compressed as described for the
In the fourth synopsis form, the characters in
are deleted from the input, and the
characters in string2
are compressed as
described for the
The following conventions can be used in
to specify sets of characters:
- Any character not described by one of the following conventions represents
- A backslash followed by 1, 2, or 3 octal digits represents a character
with that encoded value. To follow an octal sequence with a digit as a
character, left zero-pad the octal sequence to the full 3 octal
- A backslash followed by certain special characters maps to special values.
A backslash followed by any other character maps to that character.
- <alert character>
- <carriage return>
- <vertical tab>
- Represents the range of characters between the range endpoints,
- Represents all characters belonging to the defined character class. Class
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.
For specific information as to which ASCII characters are included in these
classes, see isalnum(3),
isalpha(3), and related
- <alphanumeric characters>
- <alphabetic characters>
- <blank characters>
- <control characters>
- <numeric characters>
- <graphic characters>
- <lower-case alphabetic characters>
- <printable characters>
- <punctuation characters>
- <space characters>
- <upper-case characters>
- <hexadecimal characters>
- Represents all characters or collating (sorting) elements belonging to the
same equivalence class as equiv. If there
is a secondary ordering within the equivalence class, the characters are
ordered in ascending sequence. Otherwise, they are ordered after their
encoded values. An example of an equivalence class might be
“c” and “ch” in Spanish; English has no
- Represents n repeated occurrences of the
character represented by #. This
expression is only valid when it occurs in
n is omitted or is zero, it is
interpreted as large enough to extend the
string2 sequence to the length of
n has a leading zero, it is interpreted
as an octal value; otherwise, it's interpreted as a decimal value.
utility exits 0 on success,
and >0 if an error occurs.
The following examples are shown as given to the shell:
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
Translate the contents of file1 to upper-case.
$ tr “[:lower:]”
“[:upper:]” < file1
Strip out non-printable characters from file1.
$ tr -cd “[:print:]”
utility is compliant with the
IEEE Std 1003.1-2008
specification, except that the
option behaves the same as the
is not locale-aware.
System V has historically implemented character ranges using the syntax
“[c-c]” instead of the “c-c” used by historic
implementations and standardized by POSIX. System
V shell scripts should work under this implementation as long as the range is
intended to map in another range, i.e., the command “tr [a-z]
[A-Z]” will work as it will map the ‘[’ character in
to the ‘[’ character in
. However, if the shell script is
deleting or squeezing characters as in the command
“tr -d [a-z]”, the characters ‘[’
and ‘]’ will be included in the deletion or compression list,
which would not have happened under an historic System V implementation.
Additionally, any scripts that depended on the sequence “a-z” to
represent the three characters ‘a’, ‘-’, and
‘z’ will have to be rewritten as “a\-z”.
utility has historically not permitted
the manipulation of NUL bytes in its input and, additionally, has stripped
NUL's from its input stream. This implementation has removed this behavior as
utility has historically been
extremely forgiving of syntax errors: for example, the
options were ignored unless two strings
were specified. This implementation will not permit illegal syntax.
It should be noted that the feature wherein the last character of
is duplicated if
has less characters than
is permitted by POSIX but is not
required. Shell scripts attempting to be portable to other POSIX systems
should use the “[#*]” convention instead of relying on this