1TR(P) POSIX Programmer's Manual TR(P)
2
6 tr - translate characters
7
9 tr [-c | -C][-s] string1 string2
10 tr -s [-c | -C] string1
12 tr -d [-c | -C] string1
14 tr -ds [-c | -C] string1 string2
16
19 The tr utility shall copy the standard input to the standard output
20 with substitution or deletion of selected characters. The options
21 specified and the string1 and string2 operands shall control transla‐
22 tions that occur while copying characters and single-character collat‐
23 ing elements.
24
26 The tr utility shall conform to the Base Definitions volume of
27 IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
28 The following options shall be supported:
30 -c Complement the set of values specified by string1. See the
32 EXTENDED DESCRIPTION section.
33 -C Complement the set of characters specified by string1. See the
35 EXTENDED DESCRIPTION section.
36 -d Delete all occurrences of input characters that are specified by
38 string1.
39 -s Replace instances of repeated characters with a single charac‐
41 ter, as described in the EXTENDED DESCRIPTION section.
42
45 The following operands shall be supported:
46 string1, string2
48 Translation control strings. Each string shall represent a set
50 of characters to be converted into an array of characters used
51 for the translation. For a detailed description of how the
52 strings are interpreted, see the EXTENDED DESCRIPTION section.
53
56 The standard input can be any type of file.
57
59 None.
60
62 The following environment variables shall affect the execution of tr:
63 LANG Provide a default value for the internationalization variables
65 that are unset or null. (See the Base Definitions volume of
66 IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
67 ables for the precedence of internationalization variables used
68 to determine the values of locale categories.)
69 LC_ALL If set to a non-empty string value, override the values of all
71 the other internationalization variables.
72 LC_COLLATE
74 Determine the locale for the behavior of range expressions and
76 equivalence classes.
77 LC_CTYPE
79 Determine the locale for the interpretation of sequences of
80 bytes of text data as characters (for example, single-byte as
81 opposed to multi-byte characters in arguments) and the behavior
82 of character classes.
83 LC_MESSAGES
85 Determine the locale that should be used to affect the format
86 and contents of diagnostic messages written to standard error.
87 NLSPATH
89 Determine the location of message catalogs for the processing of
90 LC_MESSAGES .
91
94 Default.
95
97 The tr output shall be identical to the input, with the exception of
98 the specified transformations.
99
101 The standard error shall be used only for diagnostic messages.
102
104 None.
105
107 The operands string1 and string2 (if specified) define two arrays of
108 characters. The constructs in the following list can be used to specify
109 characters or single-character collating elements. If any of the con‐
110 structs result in multi-character collating elements, tr shall exclude,
111 without a diagnostic, those multi-character elements from the resulting
112 array.
113 character
115 Any character not described by one of the conventions below
116 shall represent itself.
117 \octal Octal sequences can be used to represent characters with spe‐
119 cific coded values. An octal sequence shall consist of a back‐
120 slash followed by the longest sequence of one, two, or three-
121 octal-digit characters (01234567). The sequence shall cause the
122 value whose encoding is represented by the one, two, or three-
123 digit octal integer to be placed into the array. If the size of
124 a byte on the system is greater than nine bits, the valid escape
125 sequence used to represent a byte is implementation-defined.
126 Multi-byte characters require multiple, concatenated escape
127 sequences of this type, including the leading '\' for each byte.
128 \character
130 The backslash-escape sequences in the Base Definitions volume of
131 IEEE Std 1003.1-2001, Table 5-1, Escape Sequences and Associated
132 Actions ( '\\' , '\a' , '\b' , '\f' , '\n' , '\r' , '\t' , '\v'
133 ) shall be supported. The results of using any other character,
134 other than an octal digit, following the backslash are unspeci‐
135 fied.
136 c-c In the POSIX locale, this construct shall represent the range of
138 collating elements between the range endpoints (as long as nei‐
139 ther endpoint is an octal sequence of the form \octal), inclu‐
140 sive, as defined by the collation sequence. The characters or
141 collating elements in the range shall be placed in the array in
142 ascending collation sequence. If the second endpoint precedes
143 the starting endpoint in the collation sequence, it is unspeci‐
144 fied whether the range of collating elements is empty, or this
145 construct is treated as invalid. In locales other than the POSIX
146 locale, this construct has unspecified behavior.
147 If either or both of the range endpoints are octal sequences of the
149 form \octal, this shall represent the range of specific coded values
150 between the two range endpoints, inclusive.
151 :class:
153 Represents all characters belonging to the defined character
154 class, as defined by the current setting of the LC_CTYPE locale
155 category. The following character class names shall be accepted
156 when specified in string1:
157 alnum blank digit lower punct upper
159 alpha cntrl graph print space xdigit
160 In addition, character class expressions of the form [: name:] shall be
162 recognized in those locales where the name keyword has been given a
163 charclass definition in the LC_CTYPE category.
164 When both the -d and -s options are specified, any of the character
166 class names shall be accepted in string2. Otherwise, only character
167 class names lower or upper are valid in string2 and then only if the
168 corresponding character class ( upper and lower, respectively) is spec‐
169 ified in the same relative position in string1. Such a specification
170 shall be interpreted as a request for case conversion. When [: lower:]
171 appears in string1 and [: upper:] appears in string2, the arrays shall
172 contain the characters from the toupper mapping in the LC_CTYPE cate‐
173 gory of the current locale. When [: upper:] appears in string1 and [:
174 lower:] appears in string2, the arrays shall contain the characters
175 from the tolower mapping in the LC_CTYPE category of the current
176 locale. The first character from each mapping pair shall be in the
177 array for string1 and the second character from each mapping pair shall
178 be in the array for string2 in the same relative position.
179 Except for case conversion, the characters specified by a character
181 class expression shall be placed in the array in an unspecified order.
182 If the name specified for class does not define a valid character class
184 in the current locale, the behavior is undefined.
185 =equiv=
187 Represents all characters or collating elements belonging to the
188 same equivalence class as equiv, as defined by the current set‐
189 ting of the LC_COLLATE locale category. An equivalence class
190 expression shall be allowed only in string1, or in string2 when
191 it is being used by the combined -d and -s options. The charac‐
192 ters belonging to the equivalence class shall be placed in the
193 array in an unspecified order.
194 x*n Represents n repeated occurrences of the character x. Because
196 this expression is used to map multiple characters to one, it is
197 only valid when it occurs in string2. If n is omitted or is
198 zero, it shall be interpreted as large enough to extend the
199 string2-based sequence to the length of the string1-based
200 sequence. If n has a leading zero, it shall be interpreted as an
201 octal value. Otherwise, it shall be interpreted as a decimal
202 value.
203 When the -d option is not specified:
206 * Each input character found in the array specified by string1 shall
208 be replaced by the character in the same relative position in the
209 array specified by string2. When the array specified by string2 is
210 shorter that the one specified by string1, the results are unspeci‐
211 fied.
212 * If the -C option is specified, the complements of the characters
214 specified by string1 (the set of all characters in the current char‐
215 acter set, as defined by the current setting of LC_CTYPE , except
216 for those actually specified in the string1 operand) shall be placed
217 in the array in ascending collation sequence, as defined by the cur‐
218 rent setting of LC_COLLATE .
219 * If the -c option is specified, the complement of the values speci‐
221 fied by string1 shall be placed in the array in ascending order by
222 binary value.
223 * Because the order in which characters specified by character class
225 expressions or equivalence class expressions is undefined, such
226 expressions should only be used if the intent is to map several
227 characters into one. An exception is case conversion, as described
228 previously.
229 When the -d option is specified:
231 * Input characters found in the array specified by string1 shall be
233 deleted.
234 * When the -C option is specified with -d, all characters except those
236 specified by string1 shall be deleted. The contents of string2 are
237 ignored, unless the -s option is also specified.
238 * When the -c option is specified with -d, all values except those
240 specified by string1 shall be deleted. The contents of string2 shall
241 be ignored, unless the -s option is also specified.
242 * The same string cannot be used for both the -d and the -s option;
244 when both options are specified, both string1 (used for deletion)
245 and string2 (used for squeezing) shall be required.
246 When the -s option is specified, after any deletions or translations
248 have taken place, repeated sequences of the same character shall be
249 replaced by one occurrence of the same character, if the character is
250 found in the array specified by the last operand. If the last operand
251 contains a character class, such as the following example:
252 tr -s '[:space:]'
255 the last operand's array shall contain all of the characters in that
257 character class. However, in a case conversion, as described previ‐
258 ously, such as:
259 tr -s '[:upper:]' '[:lower:]'
262 the last operand's array shall contain only those characters defined as
264 the second characters in each of the toupper or tolower character
265 pairs, as appropriate.
266 An empty string used for string1 or string2 produces undefined results.
268
270 The following exit values shall be returned:
271 0 All input was processed successfully.
273 >0 An error occurred.
275
278 Default.
279 The following sections are informative.
281
283 If necessary, string1 and string2 can be quoted to avoid pattern match‐
284 ing by the shell.
285 If an ordinary digit (representing itself) is to follow an octal
287 sequence, the octal sequence must use the full three digits to avoid
288 ambiguity.
289 When string2 is shorter than string1, a difference results between his‐
291 torical System V and BSD systems. A BSD system pads string2 with the
292 last character found in string2. Thus, it is possible to do the fol‐
293 lowing:
294 tr 0123456789 d
297 which would translate all digits to the letter 'd' . Since this area is
299 specifically unspecified in this volume of IEEE Std 1003.1-2001, both
300 the BSD and System V behaviors are allowed, but a conforming applica‐
301 tion cannot rely on the BSD behavior. It would have to code the example
302 in the following way:
303 tr 0123456789 '[d*]'
306 It should be noted that, despite similarities in appearance, the string
308 operands used by tr are not regular expressions.
309 Unlike some historical implementations, this definition of the tr util‐
311 ity correctly processes NUL characters in its input stream. NUL charac‐
312 ters can be stripped by using:
313 tr -d '\000'
316
318 1. The following example creates a list of all words in file1 one per
319 line in file2, where a word is taken to be a maximal string of let‐
320 ters.
321 tr -cs "[:alpha:]" "[\n*]" <file1 >file2
324 2. The next example translates all lowercase characters in file1 to
326 uppercase and writes the results to standard output.
327 tr "[:lower:]" "[:upper:]" <file1
330 3. This example uses an equivalence class to identify accented vari‐
332 ants of the base character 'e' in file1, which are stripped of dia‐
333 critical marks and written to file2.
334 tr "[=e=]" e <file1 >file2
337
339 In some early proposals, an explicit option -n was added to disable the
340 historical behavior of stripping NUL characters from the input. It was
341 considered that automatically stripping NUL characters from the input
342 was not correct functionality. However, the removal of -n in a later
343 proposal does not remove the requirement that tr correctly process NUL
344 characters in its input stream. NUL characters can be stripped by using
345 tr -d '\000'.
346 Historical implementations of tr differ widely in syntax and behavior.
348 For example, the BSD version has not needed the bracket characters for
349 the repetition sequence. The tr utility syntax is based more closely on
350 the System V and XPG3 model while attempting to accommodate historical
351 BSD implementations. In the case of the short string2 padding, the
352 decision was to unspecify the behavior and preserve System V and XPG3
353 scripts, which might find difficulty with the BSD method. The assump‐
354 tion was made that BSD users of tr have to make accommodations to meet
355 the syntax defined here. Since it is possible to use the repetition
356 sequence to duplicate the desired behavior, whereas there is no simple
357 way to achieve the System V method, this was the correct, if not desir‐
358 able, approach.
359 The use of octal values to specify control characters, while having
361 historical precedents, is not portable. The introduction of escape
362 sequences for control characters should provide the necessary portabil‐
363 ity. It is recognized that this may cause some historical scripts to
364 break.
365 An early proposal included support for multi-character collating ele‐
367 ments. It was pointed out that, while tr does employ some syntactical
368 elements from REs, the aim of tr is quite different; ranges, for exam‐
369 ple, do not have a similar meaning (``any of the chars in the range
370 matches", versus "translate each character in the range to the output
371 counterpart"). As a result, the previously included support for multi-
372 character collating elements has been removed. What remains are ranges
373 in current collation order (to support, for example, accented charac‐
374 ters), character classes, and equivalence classes.
375 In XPG3 the [: class:] and [= equiv=] conventions are shown with double
377 brackets, as in RE syntax. However, tr does not implement RE princi‐
378 ples; it just borrows part of the syntax. Consequently, [: class:] and
379 [= equiv=] should be regarded as syntactical elements on a par with [
380 x* n], which is not an RE bracket expression.
381 The standard developers will consider changes to tr that allow it to
383 translate characters between different character encodings, or they
384 will consider providing a new utility to accomplish this.
385 On historical System V systems, a range expression requires enclosing
387 square-brackets, such as:
388 tr '[a-z]' '[A-Z]'
391 However, BSD-based systems did not require the brackets, and this con‐
393 vention is used here to avoid breaking large numbers of BSD scripts:
394 tr a-z A-Z
397 The preceding System V script will continue to work because the brack‐
399 ets, treated as regular characters, are translated to themselves. How‐
400 ever, any System V script that relied on "a-z" representing the three
401 characters 'a' , '-' , and 'z' have to be rewritten as "az-" .
402 The ISO POSIX-2:1993 standard had a -c option that behaved similarly to
404 the -C option, but did not supply functionality equivalent to the -c
405 option specified in IEEE Std 1003.1-2001. This meant that historical
406 practice of being able to specify tr -d\200-\377 (which would delete
407 all bytes with the top bit set) would have no effect because, in the C
408 locale, bytes with the values octal 200 to octal 377 are not charac‐
409 ters.
410 The earlier version also said that octal sequences referred to collat‐
412 ing elements and could be placed adjacent to each other to specify
413 multi-byte characters. However, it was noted that this caused ambigui‐
414 ties because tr would not be able to tell whether adjacent octal
415 sequences were intending to specify multi-byte characters or multiple
416 single byte characters. IEEE Std 1003.1-2001 specifies that octal
417 sequences always refer to single byte binary values.
418
420 None.
421
423 sed
424
426 Portions of this text are reprinted and reproduced in electronic form
427 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
428 -- Portable Operating System Interface (POSIX), The Open Group Base
429 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
430 Electrical and Electronics Engineers, Inc and The Open Group. In the
431 event of any discrepancy between this version and the original IEEE and
432 The Open Group Standard, the original IEEE and The Open Group Standard
433 is the referee document. The original Standard can be obtained online
434 at http://www.opengroup.org/unix/online.html .
435IEEE/The Open Group 2003 TR(P)