TR(1) BSD General Commands Manual TR(1)NAME
tr — translate characters
tr [-cs] string1 string2
tr [-c] -d string1
tr [-c] -s string1
tr [-c] -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 Complements the set of characters in string1, that is ``-c ab''
includes every character except for ``a'' and ``b''.
-d The -d option causes characters to be deleted from the input.
-s The -s option squeezes 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.
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 Represents the range of characters between the range end‐
[:class:] Represents all characters belonging to the defined character
class. Class names are:
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>
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
For specific information as to which ASCII characters are
included in these classes, see ctype(3) and related manual
[=equiv=] 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 charac‐
ters are ordered in ascending sequence. Otherwise, they are
ordered after their encoded values. An example of an equiva‐
lence class might be ``c'' and ``ch'' in Spanish; English has
no equivalence classes.
[#*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's interpreted as a decimal value.
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
Strip out non-printable characters from file1.
tr -cd "[:print:]" < file1
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 ``[''
character 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 dele‐
tion 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''.
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 is expected to be IEEE Std 1003.2 (“POSIX.2”) compatible.
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.
BSD June 6, 1993 BSD