Document that tr(1) was written for US-ASCII and may not work as

expected on other character sets which do not share ASCII's properties
(e.g. a symmetric set of capital and lower case characters), per PR 18738

Change all double quotes to nroff macros.
Change "System V" references to the .At macro.

usr.bin/tr/tr.1

@@ -1,4 +1,4 @@
-.\"	$NetBSD: tr.1,v 1.13 2003/08/07 11:16:47 agc Exp $
+.\"	$NetBSD: tr.1,v 1.14 2004/03/24 06:35:53 fair Exp $
 .\"
 .\" Copyright (c) 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -32,7 +32,7 @@
 .\"
 .\"     @(#)tr.1	8.1 (Berkeley) 6/6/93
 .\"
-.Dd June 6, 1993
+.Dd March 23, 2004
 .Dt TR 1
 .Os
 .Sh NAME
@@ -65,7 +65,12 @@ The following options are available:
 .It Fl c
 Complements the set of characters in
 .Ar string1 ,
-that is ``-c ab'' includes every character except for ``a'' and ``b''.
+that is
+.Qq \&-c \&ab
+includes every character except for
+.Qq \&a
+and
+.Qq \&b .
 .It Fl d
 The
 .Fl d
@@ -184,10 +189,16 @@ Class names are:
 \." and vice-versa) is specified in the same relative position in
 \." .Ar string1 .
 \." .Pp
-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.
+With the exception of the
+.Qq upper
+and
+.Qq lower
+classes, characters in the classes are in unspecified order.
+In the
+.Qq upper
+and
+.Qq lower
+classes, characters are entered in ascending order.
 .Pp
 For specific information as to which ASCII characters are included
 in these classes, see
@@ -197,11 +208,14 @@ and related manual pages.
 Represents all characters or collating (sorting) elements belonging to
 the same equivalence class as
 .Ar equiv .
-If
-there is a secondary ordering within the equivalence class, the characters
-are ordered in ascending sequence.
+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;
+An example of an equivalence class might be
+.Qq \&c
+and
+.Qq \&ch
+in Spanish;
 English has no equivalence classes.
 .It [#*n]
 Represents
@@ -228,38 +242,67 @@ exits 0 on success, and \*[Gt]0 if an error occurs.
 .Sh EXAMPLES
 The following examples are shown as given to the shell:
 .sp
-Create a list of the words in file1, one per line, where a word is taken to
-be a maximal string of letters.
+Create a list of the words in
+.Ar file1 ,
+one per line, where a word is taken to be a maximal string of letters:
 .sp
 .D1 Li "tr -cs \*q[:alpha:]\*q \*q\en\*q \*[Lt] file1"
 .sp
-Translate the contents of file1 to upper-case.
+Translate the contents of
+.Ar file1
+to upper-case:
 .sp
 .D1 Li "tr \*q[:lower:]\*q \*q[:upper:]\*q \*[Lt] file1"
 .sp
-Strip out non-printable characters from file1.
+Strip out non-printable characters from
+.Ar file1 :
 .sp
 .D1 Li "tr -cd \*q[:print:]\*q \*[Lt] file1"
 .Sh COMPATIBILITY
-System V has historically implemented character ranges using the syntax
-``[c-c]'' instead of the ``c-c'' used by historic
+.At V
+has historically implemented character ranges using the syntax
+.Qq [c-c]
+instead of the
+.Qq c-c
+used by historic
 .Bx
-implementations and
-standardized by POSIX.
+implementations and standardized by POSIX.
 .At 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
+.Pp
+.Ic "tr [a-z] [A-Z]"
+.Pp
+will work as it will map the
+.Qq \&[
+character in
 .Ar string1
-to the ``['' character in
+to the
+.Qq \&[
+character in
 .Ar string2 .
 However, if the shell script is deleting 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\e-z''.
+the command
+.Pp
+.Ic "tr -d [a-z]"
+.Pp
+the characters
+.Qq \&[
+and
+.Qq \&]
+will be included in the deletion or compression list which would
+not have happened under an historic
+.At V
+implementation.
+Additionally, any scripts that depended on the sequence
+.Qq a-z
+to represent the three characters
+.Qq \&a ,
+.Qq \&- ,
+and
+.Qq \&z
+will have to be rewritten as
+.Qq a\e-z .
 .Pp
 The
 .Nm
@@ -290,4 +333,19 @@ has less characters than
 .Ar 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
+.Qq [#*]
+convention instead of relying on this behavior.
+.Sh BUGS
+.Nm
+was originally designed to work with
+.Tn US-ASCII .
+Its use with character sets that do not share all the properties of
+.Tn US-ASCII ,
+e.g.
+a symmetric set of upper and lower case characters
+that can be algorithmically converted one to the other,
+may yield unpredictable results.
+.Pp
+.Nm
+should be internationalized.