Originální popis anglicky:
tr - translate characters
Návod, kniha: POSIX Programmer's Manual
tr [-c | -C][-s] string1
string2
tr -s
[-c | -C]
string1
tr -d
[-c | -C]
string1
tr -ds
[-c | -C] string1
string2
The
tr utility shall copy the standard input to the standard output with
substitution or deletion of selected characters. The options specified and the
string1 and
string2 operands shall control translations that
occur while copying characters and single-character collating elements.
The
tr utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
- -c
- Complement the set of values specified by string1.
See the EXTENDED DESCRIPTION section.
- -C
- Complement the set of characters specified by
string1. See the EXTENDED DESCRIPTION section.
- -d
- Delete all occurrences of input characters that are
specified by string1.
- -s
- Replace instances of repeated characters with a single
character, as described in the EXTENDED DESCRIPTION section.
The following operands shall be supported:
- string1, string2
-
Translation control strings. Each string shall represent a set of characters
to be converted into an array of characters used for the translation. For
a detailed description of how the strings are interpreted, see the
EXTENDED DESCRIPTION section.
The standard input can be any type of file.
None.
The following environment variables shall affect the execution of
tr:
- LANG
- Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables used to
determine the values of locale categories.)
- LC_ALL
- If set to a non-empty string value, override the values of
all the other internationalization variables.
- LC_COLLATE
-
Determine the locale for the behavior of range expressions and equivalence
classes.
- LC_CTYPE
- Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as opposed to
multi-byte characters in arguments) and the behavior of character
classes.
- LC_MESSAGES
- Determine the locale that should be used to affect the
format and contents of diagnostic messages written to standard error.
- NLSPATH
- Determine the location of message catalogs for the
processing of LC_MESSAGES .
Default.
The
tr output shall be identical to the input, with the exception of the
specified transformations.
The standard error shall be used only for diagnostic messages.
None.
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 shall exclude, without
a diagnostic, those multi-character elements from the resulting array.
- character
- Any character not described by one of the conventions below
shall represent itself.
- \octal
- Octal sequences can be used to represent characters with
specific coded values. An octal sequence shall consist of a backslash
followed by the longest sequence of one, two, or three-octal-digit
characters (01234567). The sequence shall cause the value whose encoding
is represented by the one, two, or three-digit octal integer to be placed
into the array. If the size of a byte on the system is greater than nine
bits, the valid escape sequence used to represent a byte is
implementation-defined. Multi-byte characters require multiple,
concatenated escape sequences of this type, including the leading
'\' for each byte.
- \character
- The backslash-escape sequences in the Base Definitions
volume of IEEE Std 1003.1-2001, Table 5-1, Escape Sequences
and Associated Actions ( '\\' , '\a' , '\b' ,
'\f' , '\n' , '\r' , '\t' , '\v' )
shall be supported. The results of using any other character, other than
an octal digit, following the backslash are unspecified.
- c-c
- In the POSIX locale, this construct shall represent the
range of collating elements between the range endpoints (as long as
neither endpoint is an octal sequence of the form \ octal),
inclusive, as defined by the collation sequence. The characters or
collating elements in the range shall be 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, this shall represent the range of specific coded values between
the two range endpoints, inclusive.
- :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 shall 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:] shall be
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 shall 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 shall be interpreted as a request for
case conversion. When [:
lower:] appears in
string1 and [:
upper:] appears in
string2, the arrays shall 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 shall contain the
characters from the
tolower mapping in the
LC_CTYPE category of
the current locale. The first character from each mapping pair shall be in the
array for
string1 and the second character from each mapping pair shall
be in the array for
string2 in the same relative position.
Except for case conversion, the characters specified by a character class
expression shall be 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 shall be 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 shall be 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 zero, it shall be interpreted as large enough to extend the
string2-based sequence to the length of the string1-based
sequence. If n has a leading zero, it shall be interpreted as an
octal value. Otherwise, it shall be interpreted as a decimal value.
When the
-d option is not specified:
- *
- Each input character found in the array specified by
string1 shall be 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) shall be placed in the array in ascending
collation sequence, as defined by the current setting of LC_COLLATE
.
- *
- If the -c option is specified, the complement of the
values specified by string1 shall be placed in the array in
ascending order by binary value.
- *
- 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 shall be deleted.
- *
- When the -C option is specified with -d, all
characters except those specified by string1 shall be deleted. The
contents of string2 are ignored, unless the -s option is
also specified.
- *
- When the -c option is specified with -d, all
values except those specified by string1 shall be deleted. The
contents of string2 shall 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) shall be
required.
When the
-s option is specified, after any deletions or translations have
taken place, repeated sequences of the same character shall 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:
the last operand's array shall 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 shall 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 exit values shall be returned:
- 0
- All input was processed successfully.
- >0
- An error occurred.
Default.
The following sections are informative.
If necessary,
string1 and
string2 can be quoted to avoid pattern
matching by the shell.
If an ordinary digit (representing itself) is to follow an octal sequence, the
octal sequence must use the full three digits to avoid ambiguity.
When
string2 is shorter than
string1, a difference results between
historical System V and BSD systems. A BSD system pads
string2
with the last character found in
string2. Thus, it is possible to do
the following:
which would translate all digits to the letter
'd' . Since this area is
specifically unspecified in this volume of IEEE Std 1003.1-2001,
both the BSD and System V behaviors are allowed, but a conforming
application cannot rely on the BSD behavior. It would have to code the example
in the following way:
It should be noted that, despite similarities in appearance, the string operands
used by
tr are not regular expressions.
Unlike some historical implementations, this definition of the
tr utility
correctly processes NUL characters in its input stream. NUL characters can be
stripped by using:
- 1.
- 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
- 2.
- The next example translates all lowercase characters in
file1 to uppercase and writes the results to standard output.
tr "[:lower:]" "[:upper:]" <file1
- 3.
- 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
In some early proposals, an explicit option
-n was added to disable the
historical behavior of stripping NUL characters from the input. It was
considered that automatically stripping NUL characters from the input was not
correct functionality. However, the removal of
-n in a later proposal
does not remove the requirement that
tr correctly process NUL
characters in its input stream. NUL characters can be stripped by using
tr -d '\000'.
Historical implementations of
tr differ widely in syntax and behavior.
For example, the BSD version has not needed the bracket characters for the
repetition sequence. The
tr utility syntax is based more closely on the
System V and XPG3 model while attempting to accommodate historical BSD
implementations. In the case of the short
string2 padding, the decision
was to unspecify the behavior and preserve System V and XPG3 scripts, which
might find difficulty with the BSD method. The assumption was made that BSD
users of
tr have to make accommodations to meet the syntax defined
here. Since it is possible to use the repetition sequence to duplicate the
desired behavior, whereas there is no simple way to achieve the System V
method, this was the correct, if not desirable, approach.
The use of octal values to specify control characters, while having historical
precedents, is not portable. The introduction of escape sequences for control
characters should provide the necessary portability. It is recognized that
this may cause some historical scripts to break.
An early proposal included support for multi-character collating elements. It
was pointed out that, while
tr does employ some syntactical elements
from REs, the aim of
tr is quite different; ranges, for example, do not
have a similar meaning (``any of the chars in the range matches",
versus "translate each character in the range to the output
counterpart"). As a result, the previously included support for
multi-character collating elements has been removed. What remains are ranges
in current collation order (to support, for example, accented characters),
character classes, and equivalence classes.
In XPG3 the [:
class:] and [=
equiv=] conventions are shown with
double brackets, as in RE syntax. However,
tr does not implement RE
principles; it just borrows part of the syntax. Consequently, [:
class:] and [=
equiv=] should be regarded as syntactical
elements on a par with [
x*
n], which is not an RE bracket
expression.
The standard developers will consider changes to
tr that allow it to
translate characters between different character encodings, or they will
consider providing a new utility to accomplish this.
On historical System V systems, a range expression requires enclosing
square-brackets, such as:
However, BSD-based systems did not require the brackets, and this convention is
used here to avoid breaking large numbers of BSD scripts:
The preceding System V script will continue to work because the brackets,
treated as regular characters, are translated to themselves. However, any
System V script that relied on
"a-z" representing the three
characters
'a' ,
'-' , and
'z' have to be rewritten as
"az-" .
The ISO POSIX-2:1993 standard had a
-c option that behaved
similarly to the
-C option, but did not supply functionality equivalent
to the
-c option specified in IEEE Std 1003.1-2001. This
meant that historical practice of being able to specify
tr
-d\200-\377 (which would delete all bytes with the top bit set) would
have no effect because, in the C locale, bytes with the values octal 200 to
octal 377 are not characters.
The earlier version also said that octal sequences referred to collating
elements and could be placed adjacent to each other to specify multi-byte
characters. However, it was noted that this caused ambiguities because
tr would not be able to tell whether adjacent octal sequences were
intending to specify multi-byte characters or multiple single byte characters.
IEEE Std 1003.1-2001 specifies that octal sequences always refer
to single byte binary values.
None.
sed
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html
.
