TR(1) | General Commands Manual | TR(1) |
tr
— translate
characters
tr |
[-cs ] string1 string2 |
tr |
[-c ] -d
string1 |
tr |
[-c ] -s
string1 |
tr |
[-c ] -ds
string1 string2 |
The tr
utility copies the standard input
to the standard output with substitution or deletion of selected
characters.
The following options are available:
-c
-c
ab includes every
character except for ‘a’ and ‘b’.-d
-d
option causes characters to be deleted from
the input.-s
-s
option squeezes multiple occurrences of the
characters listed in the last operand (either
string1 or string2) in the
input into a single instance of the character. This occurs after all
deletion and translation is completed.In the first synopsis form, the characters in string1 are translated into the characters in string2, where the first character in string1 is translated into the first character in string2, and so on. If string1 is longer than string2, the last character found in string2 is duplicated until string1 is exhausted.
In the second synopsis form, the characters in string1 are deleted from the input.
In the third synopsis form, the characters in
string1 are compressed as described for the
-s
option.
In the fourth synopsis form, the characters in
string1 are deleted from the input, and the characters
in string2 are compressed as described for the
-s
option.
The following conventions can be used in string1 and string2 to specify sets of characters:
\a | <alert character> |
\b | <backspace> |
\f | <form-feed> |
\n | <newline> |
\r | <carriage return> |
\t | <tab> |
\v | <vertical tab> |
A backslash followed by any other character maps to that character.
alnum | <alphanumeric characters> |
alpha | <alphabetic characters> |
blank | <blank characters> |
cntrl | <control characters> |
digit | <numeric characters> |
graph | <graphic characters> |
lower | <lower-case alphabetic characters> |
<printable characters> | |
punct | <punctuation characters> |
space | <space characters> |
upper | <upper-case alphabetic characters> |
xdigit | <hexadecimal characters> |
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.
For specific information as to which ASCII characters are included in these classes, see ctype(3) and related manual pages.
The tr
utility exits 0 on success,
and >0 if an error occurs.
The following examples are shown as given to the shell:
Create a list of the words in file1, one per line, where a word is taken to be a maximal string of letters:
tr -cs "[:alpha:]"
"\n" < file1
Translate the contents of file1 to upper-case:
tr "[:lower:]"
"[:upper:]" < file1
Strip out non-printable characters from file1:
tr -cd "[:print:]" <
file1
AT&T System V UNIX has historically implemented character ranges using the syntax “[c-c]” instead of the “c-c” used by historic BSD implementations and standardized by POSIX. AT&T System V UNIX 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 string1 to the ‘[’ character in 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 AT&T System V UNIX 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\-z”.
The tr
utility has historically not
permitted the manipulation of NUL bytes in its input and, additionally,
stripped NULs from its input stream. This implementation has removed this
behavior as a bug.
The tr
utility has historically been
extremely forgiving of syntax errors, for example, the
-c
and -s
options were
ignored unless two strings were specified. This implementation will not
permit illegal syntax.
The tr
utility is expected to be
IEEE Std 1003.2 (“POSIX.2”)
compatible. It should be noted that the feature wherein the last character
of string2 is duplicated if
string2 has less characters than
string1 is permitted by POSIX but is not required.
Shell scripts attempting to be portable to other POSIX systems should use
the “[#*n]” convention instead of relying on this
behavior.
tr
was originally designed to work with
US-ASCII. Its use with character sets that do not share all the properties
of 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.
tr
should be internationalized.
June 14, 2021 | NetBSD 10.99 |