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 substitution
or deletion of selected characters.
The options are as follows:
-c Complements the set of characters in string1; for
``-c ab'' includes every character except for ``a''
-d The -d option causes characters to be deleted from
-s The -s option squeezes multiple occurrences of the
listed in the last operand (either string1 or
string2) in the input
into a single instance of the character. This
all deletion and translation is completed.
In the first synopsis form, the characters in string1 are
the characters in string2 where the first character in
string1 is translated
into the first character in string2 and so on. If
longer than string2, the last character found in string2 is
until string1 is exhausted.
In the second synopsis form, the characters in string1 are
In the third synopsis form, the characters in string1 are
described for the -s option.
In the fourth synopsis form, the characters in string1 are
the input, and the characters in string2 are compressed as
the -s option.
The following conventions can be used in string1 and string2
sets of characters:
character Any character not described by one of the following conventions
aAakslash followed by 1, 2, or 3 octal digits represents a
character with that encoded value. To follow an
with a digit as a character, left zero-pad
sequence to the full 3 octal digits.
A backslash followed by certain special
characters maps to
A backslash followed by any other character maps
to that character.
c-c Represents the range of characters between the
[:class:] Represents all characters belonging to the defined character
class. Class names are:
alnum <alphanumeric characters>
alpha <alphabetic characters>
blank <blank 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''
characters in the classes are in unspecified order. In the
``upper'' and ``lower'' classes, characters are
entered in ascending
For specific information as to which ASCII characters are included
in these classes, see ctype(3) and related
[=equiv=] Represents all characters or collating (sorting)
to the same equivalence class as equiv.
If there is a
secondary ordering within the equivalence class,
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;
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
large enough to extend string2 sequence to the
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 or >0 if an error occurred.
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:]" "0 < 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
``[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
``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
on the sequence ``a-z'' to represent the three characters
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, has stripped NUL's
from its input
stream. This implementation has removed this behavior as a
The tr utility has historically been extremely forgiving of
for example, the -c and -s options were ignored unless
were specified. This implementation will not permit illegal
The tr utility is expected to be IEEE Std 1003.2
It should be noted that the feature wherein the last
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.
OpenBSD 3.6 June 6, 1993
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