TR(1) BSD General Commands Manual TR(1)NAMEtr — translate characters
SYNOPSIStr [-Ccsu] string1 string2
tr [-Ccu] -d string1
tr [-Ccu] -s string1
tr [-Ccu] -ds string1 string2
The tr utility copies the standard input to the standard output with sub‐
stitution or deletion of selected characters.
The following options are available:
-C Complement the set of characters in string1, that is “-C ab”
includes every character except for ‘a’ and ‘b’.
-c Same as -C but complement the set of values in string1.
-d Delete characters in string1 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.
-u Guarantee that any output is unbuffered.
In the first synopsis form, the characters in string1 are translated into
the characters in string2 where the first character in string1 is trans‐
lated 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
In the third synopsis form, the characters in string1 are compressed as
described for the -s option.
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.
The following conventions can be used in string1 and string2 to specify
sets of characters:
character Any character not described by one of the following conven‐
tions represents itself.
\octal 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 digits.
A backslash followed by certain special characters maps to
\a <alert character>
\r <carriage return>
\v <vertical tab>
A backslash followed by any other character maps to that char‐
c-c For non-octal range endpoints represents the range of charac‐
ters between the range endpoints, inclusive, in ascending
order, as defined by the collation sequence. If either or
both of the range endpoints are octal sequences, it represents
the range of specific coded values between the range end‐
See the COMPATIBILITY section below for an important note
regarding differences in the way the current implementation
interprets range expressions differently from previous imple‐
[:class:] Represents all characters belonging to the defined character
class. Class names are:
alnum <alphanumeric characters>
alpha <alphabetic characters>
blank <whitespace characters>
cntrl <control characters>
digit <numeric characters>
graph <graphic characters>
ideogram <ideographic characters>
lower <lower-case alphabetic characters>
phonogram <phonographic characters>
print <printable characters>
punct <punctuation characters>
rune <valid characters>
space <space characters>
special <special characters>
upper <upper-case characters>
xdigit <hexadecimal characters>
When “[:lower:]” appears in string1 and “[:upper:]” appears in
the same relative position in string2, it represents the char‐
acters pairs from the toupper mapping in the LC_CTYPE category
of the current locale. When “[:upper:]” appears in string1
and “[:lower:]” appears in the same relative position in
string2, it represents the characters pairs from the tolower
mapping in the LC_CTYPE category of the current locale.
With the exception of case conversion, characters in the
classes are in unspecified order.
For specific information as to which ASCII characters are
included in these classes, see ctype(3) and related manual
[=equiv=] Represents all characters belonging to the same equivalence
class as equiv, ordered by their encoded values.
[#*n] Represents n repeated occurrences of the character represented
by #. This expression is only valid when it occurs in
string2. If n is omitted or is zero, it is be interpreted as
large enough to extend string2 sequence to the length of
string1. If n has a leading zero, it is interpreted as an
octal value, otherwise, it is interpreted as a decimal value.
The LANG, LC_ALL, LC_CTYPE and LC_COLLATE environment variables affect
the execution of tr as described in environ(7).
The tr 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
(This should be preferred over the traditional UNIX idiom of “tr a-z A-
Z”, since it works correctly in all locales.)
Strip out non-printable characters from file1.
tr-cd "[:print:]" < file1
Remove diacritical marks from all accented variants of the letter ‘e’:
tr "[=e=]" "e"
Previous FreeBSD implementations of tr did not order characters in range
expressions according to the current locale's collation order, making it
possible to convert unaccented Latin characters (esp. as found in English
text) from upper to lower case using the traditional UNIX idiom of “tr A-
Z a-z”. Since tr now obeys the locale's collation order, this idiom may
not produce correct results when there is not a 1:1 mapping between lower
and upper case, or when the order of characters within the two cases dif‐
fers. As noted in the EXAMPLES section above, the character class
expressions “[:lower:]” and “[:upper:]” should be used instead of
explicit character ranges like “a-z” and “A-Z”.
System V has historically implemented character ranges using the syntax
“[c-c]” instead of the “c-c” used by historic BSD 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 ‘[’ char‐
acter in string1 to the ‘[’ character in string2. 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 com‐
pression list which would not have happened under a 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”.
The tr utility has historically not permitted the manipulation of NUL
bytes in its input and, additionally, stripped NUL's from its input
stream. This implementation has removed this behavior as a bug.
The tr utility has historically been extremely forgiving of syntax
errors, for example, the -c and -s options were ignored unless two
strings were specified. This implementation will not permit illegal syn‐
The tr utility conforms to IEEE Std 1003.1-2001 (“POSIX.1”). The
“ideogram”, “phonogram”, “rune”, and “special” character classes are
It should be noted that the feature wherein the last character of string2
is duplicated if string2 has less characters than string1 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 behavior. The -u option is an extension to the IEEE Std
1003.1-2001 (“POSIX.1”) standard.
BSD October 13, 2006 BSD