tr -- Command

Translate characters
tr [-cds] string1 [string2]

tr reads  characters from the  standard input, possibly  translates each to
another value or deletes it, and writes to standard output.

Each specified  string may contain literal  characters of the form  a or \b
(where b  is non-numeric), octal representations of the  form \ooo (where o
is an octal digit), and character  ranges of the form X-Y. tr rewrites each
string with the appropriate conversions and range expansions.

If an input character is in string1, tr outputs the corresponding character
of string2.  If string2  is shorter  than string1, the  result is  the last
character in string2.

The following flags control how tr translates characters:

-c Replace string1 by the set of characters not in string1.

-d Delete characters in string1 rather than translating them.

-s The  ``squeeze''  option: map  a  sequence of  the  same character  from
   string1 to one output character.

Example

The  following example  prints  all sequences  of  four or  more spaces  or
printing characters from infile:

    tr -cs ' -~' '\12' <infile | grep ....

Here string1  is the  range from <space>  to `~', which  includes all
printing  characters.  Because  this example  uses the  flags -cs,  tr maps
sequences of nonprinting characters to newline (octal 12).

See Also

ASCII,
commands,
ctype.h,
sed

Notes

Beginning with COHERENT 4.2, the command

    echo "This is a test." | tr

returns

    This is a test.

This behavior  does not conform with  POSIX Standard, but is  required by a
number of third-party packages.

© 2012 by Stephen A. Ness