tr(1) manual page
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tr - translate characters
/usr/bin/tr [-cs] string1 string2
/usr/bin/tr -s|-d [-c] string1
/usr/bin/tr -ds [-c] string1 string2
/usr/bin/xpg4/tr [-cs] string1 string2
/usr/bin/xpg4/tr -s|-d [-c] string1
/usr/bin/xpg4/tr -ds [-c] string1 string2
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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.
The following options are supported:
- -c
- Complement the set
of characters specified by string1.
- -d
- Delete all occurrences of input characters
that are specified by string1.
- -s
- Replace instances of repeated characters
with a single character.
When the -d option is not specified:
- 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 that the one specified by string1,
the results are unspecified.
- 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
. 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:
- Input characters found in the array specified
by string1 will be deleted.
- When the -c option is specified with -d, all characters
except those specified by string1 will be deleted.
- The contents of string2
will be ignored, unless the -s option is also specified.
- 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 will be 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 will contain 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 will contain only those characters defined as the
second characters in each of the toupper or tolower character pairs, as
appropriate.
An empty string used for string1 or string2 produces undefined
results.
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 will exclude, 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.
- c-c
-
- [c-c]
- Represents
the range of collating elements between the range endpoints, inclusive,
as defined by the current setting of the LC_COLLATE
locale category. The
starting endpoint must precede the second endpoint in the current collation
order.
The characters or collating elements in the range are placed in the array
in ascending collation sequence.
- [: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 will be 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 will be 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 will 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 will contain the characters from the tolower mapping in the
LC_CTYPE
category of the current locale. The first character from each
mapping pair will be in the array for string1 and the second character
from each mapping pair will be 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 is omitted or is 0, it is interpreted as
large enough to extend the string2-based sequence to the length of the string1-based
sequence. If n has a leading 0, it is interpreted as an octal value. Otherwise,
it is interpreted as a decimal value.
.- 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
.- The next example translates all lower-case characters in file1 to upper-case
and writes the results to standard output.
tr "[:lower:]" "[:upper:]" <file1
Note that the caveat expressed in the corresponding example 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).
.- 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
See environ(5)
for descriptions of the following environment
variables that affect the execution of tr: LC_COLLATE, LC_CTYPE, LC_MESSAGES,
and NLSPATH.
The following exit values are returned:
- All input
was processed successfully.
- >0
- An error occurred.
ed(1)
, sed(1)
, sh(1)
,
ascii(5)
, environ(5)
Will not handle ASCII
NUL
in string1 or string2;
always deletes NUL
from input.
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