Tribblix: manual page: tr.1

TR(1) User Commands TR(1)

NAME

tr - translate characters

SYNOPSIS

/usr/bin/tr [-cds] [string1 [string2]]

/usr/xpg4/bin/tr [-cs] string1 string2

/usr/xpg4/bin/tr -s | -d [-c] string1

/usr/xpg4/bin/tr -ds [-c] string1 string2

/usr/xpg6/bin/tr [-c | -C] [-s] string1 string2

/usr/xpg6/bin/tr -s [-c | -C] string1

/usr/xpg6/bin/tr -d [-c | -C] string1

/usr/xpg6/bin/tr -ds [-c | -C] string1 string2

DESCRIPTION

The tr utility copies the standard input to the standard output with
substitution or deletion of selected characters. The options
specified and the string1 and string2 operands control translations
that occur while copying characters and single-character collating
elements.

OPTIONS

The following options are supported:

-c
Complements the set of values specified by string1.

-C
Complements the set of characters specified by string1.

-d
Deletes all occurrences of input characters that are specified
by string1.

-s
Replaces instances of repeated characters with a single
character.

When the -d option is not specified:

o Each input character found in the array specified by
string1 is replaced by the character in the same relative
position in the array specified by string2. When the array
specified by string2 is shorter than the one specified by
string1, the results are unspecified.

o If the -c option is specified, the complements of the
values specified by string1 are placed in the array in
ascending order by binary value.

o If the -C option is specified, the complements of the
characters specified by string1 (the set of all characters
in the current character set, as defined by the current
setting of LC_CTYPE, except for those actually specified
in the string1 operand) are placed in the array in
ascending collation sequence, as defined by the current
setting of LC_COLLATE.

o Because the order in which characters specified by
character class expressions or equivalence class
expressions is undefined, such expressions should only be
used if the intent is to map several characters into one.
An exception is case conversion, as described previously.

When the -d option is specified:

o Input characters found in the array specified by string1
are deleted.

o When the -C option is specified with -d, all values except
those specified by string1 are deleted. The contents of
string2 are ignored, unless the -s option is also
specified.

o If the -c option is specified, the complements of the
values specified by string1 are placed in the array in
ascending order by binary value.

o The same string cannot be used for both the -d and the -s
option. When both options are specified, both string1
(used for deletion) and string2 (used for squeezing) are
required.

When the -s option is specified, after any deletions or translations
have taken place, repeated sequences of the same character is
replaced by one occurrence of the same character, if the character is
found in the array specified by the last operand. If the last operand
contains a character class, such as the following example:

tr -s '[:space:]'

the last operand's array contains all of the characters in that
character class. However, in a case conversion, as described
previously, such as

tr -s '[:upper:]' '[:lower:]'

the last operand's array contains only those characters defined as
the second characters in each of the toupper or tolower character
pairs, as appropriate. (See toupper(3C) and tolower(3C)).

An empty string used for string1 or string2 produces undefined
results.

OPERANDS

The following operands are supported:

string1
string2
Translation control strings. Each string represents a set
of characters to be converted into an array of characters
used for the translation.

The operands string1 and string2 (if specified) define two arrays of
characters. The constructs in the following list can be used to
specify characters or single-character collating elements. If any of
the constructs result in multi-character collating elements, tr
excludes, without a diagnostic, those multi-character elements from
the resulting array.

character
Any character not described by one of the conventions
below represents itself.

\octal
Octal sequences can be used to represent characters
with specific coded values. An octal sequence
consists of a backslash followed by the longest
sequence of one-, two-, or three-octal-digit
characters (01234567). The sequence causes the
character whose encoding is represented by the one-,
two- or three-digit octal integer to be placed into
the array. Multi-byte characters require multiple,
concatenated escape sequences of this type, including
the leading \ for each byte.

\character
The backslash-escape sequences \a, \b, \f, \n, \r, \t,
and \v are supported. The results of using any other
character, other than an octal digit, following the
backslash are unspecified.

/usr/xpg4/bin/tr
c-c

/usr/bin/tr
[c-c]
In the POSIX locale, this construct represents the range
of collating elements between the range endpoints (as
long as neither endpoint is an octal sequence of the
form \octal), inclusively, as defined by the collation
sequence. The characters or collating elements in the
range are placed in the array in ascending collation
sequence. If the second endpoint precedes the starting
endpoint in the collation sequence, it is unspecified
whether the range of collating elements is empty, or
this construct is treated as invalid. In locales other
than the POSIX locale, this construct has unspecified
behavior.

If either or both of the range endpoints are octal
sequences of the form \octal, represents the range of
specific coded binary values between two range
endpoints, inclusively.

[:class:]
Represents all characters belonging to the defined
character class, as defined by the current setting of
the LC_CTYPE locale category. The following character
class names are accepted when specified in string1:

alnum blank digit lower punct upper
alpha cntrl graph print space xdigit

In addition, character class expressions of the form
[:name:] are recognized in those locales where the name
keyword has been given a charclass definition in the
LC_CTYPE category.

When both the -d and -s options are specified, any of
the character class names are accepted in string2.
Otherwise, only character class names lower or upper are
valid in string2 and then only if the corresponding
character class upper and lower, respectively, is
specified in the same relative position in string1. Such
a specification is interpreted as a request for case
conversion. When [:lower:] appears in string1 and
[:upper:] appears in string2, the arrays contain the
characters from the toupper mapping in the LC_CTYPE
category of the current locale. When [:upper:] appears
in string1 and [:lower:] appears in string2, the arrays
contain the characters from the tolower mapping in the
LC_CTYPE category of the current locale. The first
character from each mapping pair is in the array for
string1 and the second character from each mapping pair
is in the array for string2 in the same relative
position.

Except for case conversion, the characters specified by
a character class expression are placed in the array in
an unspecified order.

If the name specified for class does not define a valid
character class in the current locale, the behavior is
undefined.

[=equiv=]
Represents all characters or collating elements
belonging to the same equivalence class as equiv, as
defined by the current setting of the LC_COLLATE locale
category. An equivalence class expression is allowed
only in string1, or in string2 when it is being used by
the combined -d and -s options. The characters belonging
to the equivalence class are placed in the array in an
unspecified order.

[x*n]
Represents n repeated occurrences of the character x.
Because this expression is used to map multiple
characters to one, it is only valid when it occurs in
string2. If n has a leading 0, it is interpreted as an
octal value. Otherwise, it is interpreted as a decimal
value.

If n is omitted or is 0, /usr/bin/tr interprets this as
huge; /usr/xpg4/bin/tr and /usr/xpg6/bin/tr interprets
this as large enough to extend the string2-based
sequence to the length of the string1-based sequence.

USAGE

See largefile(7) for the description of the behavior of tr when
encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).

EXAMPLES

Example 1: Creating a list of words

The following example creates a list of all words in file1, one per
line in file2, where a word is taken to be a maximal string of
letters.

tr -cs "[:alpha:]" "[\n*]" <file1 >file2

Example 2: Translating characters

This example translates all lower-case characters in file1 to upper-
case and writes the results to standard output.

tr "[:lower:]" "[:upper:]" <file1

Notice that the caveat expressed in the corresponding example in XPG3
is no longer in effect. This case conversion is now a special case
that employs the tolower and toupper classifications, ensuring that
proper mapping is accomplished (when the locale is correctly
defined).

Example 3: Identifying equivalent characters

This example uses an equivalence class to identify accented variants
of the base character e in file1, which are stripped of diacritical
marks and written to file2.

tr "[=e=]" e <file1 >file2

ENVIRONMENT VARIABLES

See environ(7) for descriptions of the following environment
variables that affect the execution of tr: LANG, LC_ALL, LC_COLLATE,
LC_CTYPE, LC_MESSAGES, and NLSPATH.

EXIT STATUS

The following exit values are returned:

0
All input was processed successfully.

>0
An error occurred.

ATTRIBUTES

NOTES

Unlike some previous versions, /usr/xpg4/bin/tr correctly processes
NUL characters in its input stream. NUL characters can be stripped by
using tr -d '\000'.

June 13, 2021 TR(1)