TR(1) BSD General Commands Manual TR(1)
tr -- translate characters
tr [-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 substitution or dele-
tion of selected characters.
The following options are available:
-C Complement the set of characters in string1, that is ``-C ab'' includes every char-
acter except for ``a'' and ``b''.
-c Same as -C but complement the set of byte 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 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
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 conventions represents
\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 special values.
\a <alert character>
\r <carriage return>
\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. 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>
With the exception of the ``upper'' and ``lower'' classes, characters in the
classes are in unspecified order. In the ``upper'' and ``lower'' classes, char-
acters are entered in ascending order.
For specific information as to which ASCII characters are included in these
classes, see ctype(3) and related manual pages.
[=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, other-
wise, it's 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 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
Remove diacritical marks from all accented variants of the letter 'e':
tr "[=e=]" "e"
The tr utility exits 0 on success, and >0 if an error occurs.
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 delet-
ing 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''.
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 syntax.
The tr utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').
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 11, 1997 BSD