- Tr (Unix)
tr (abbreviated from translate or transliterate) is a command in
Unix-like operating systems.When executed, the program reads from the standard input and writes to the standard output. It takes as parameters two sets of characters, and replaces occurrences of the characters in the first set with the corresponding elements from the other set.
Examples
The following inputs shift the input letters of the alphabet forward by seven characters.
$ echo cheer | tr abcdefghijklmnopqrstuvwxyz hijklmnopqrstuvwxyzabcdefg jolly
If your tr complies
POSIX , you can simply replace the last two words with a-z h-za-g.Translate " " to " ":
$ tr -A '12' '1512' < input1 > output1 $ tr -A '^M' '1512' < output1 > output2
Notice that not all versions of tr support -A option. And also, you do not want to use double quotes, instead of single quotes, because they could make your shell evaluate backslashes between them. Notice , 12 and ^M being representations of a line feed in "character escape code", "ASCII octal" and "
caret notation ", respectively; and 15 being representations of acarriage return . For background on the need for this translation, see "newline ".The following inputs shift the input letters of the alphabet back by one character.
$ echo "ibm 9000" >computer.txt $ tr a-z za-y
hal 9000 In some older versions of tr (not
POSIX -compliant), the character ranges must be enclosed in brackets, which must then be quoted against interpretation by the shell:$ tr " [a-z] " "z [a-y] "
ROT13 can be portably implemented as tr " [A-M] [N-Z] [a-m] [n-z] " " [N-Z] [A-M] [n-z] [a-m] ". (This works because the brackets, which are not part of the range syntax in POSIX tr, align properly in the two strings, and hence will be safely interpreted as a request to map the bracket character to itself.)Ruby and
Perl also have an internal tr operator, which operates analogously.ee also
*
Sed
*List of Unix programs External links
* [http://www.linfo.org/tr.html The tr Command] - by The Linux Information Project (LINFO)
* [http://www.linuxmanpages.com/man1/tr.1.php] The program'smanpage
* [http://www.softpanorama.org/Tools/tr.shtml] Softpanorama tr page
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