The
tr utility copies the standard input to the standard output with substitution 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 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 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 conventions 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.
\character
A backslash followed by certain special characters maps to special values.
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 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>
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 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 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 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 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.