tr is a
command
Command may refer to:
Computing
* Command (computing), a statement in a computer language
* COMMAND.COM, the default operating system shell and command-line interpreter for DOS
* Command key, a modifier key on Apple Macintosh computer keyboards
* ...
in
Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
,
Plan 9,
Inferno
Inferno may refer to:
* Hell, an afterlife place of suffering
* Conflagration, a large uncontrolled fire
Film
* ''L'Inferno'', a 1911 Italian film
* Inferno (1953 film), ''Inferno'' (1953 film), a film noir by Roy Ward Baker
* Inferno (1973 fi ...
, and
Unix-like
A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...
operating systems. It is an abbreviation of ''translate'' or ''transliterate'', indicating its operation of replacing or removing specific characters in its input data set.
Overview
The utility reads a byte stream from its
standard input
In computer programming, standard streams are interconnected input and output communication channels between a computer program and its environment when it begins execution. The three input/output (I/O) connections are called standard input (stdin ...
and writes the result to the
standard output
In computer programming, standard streams are interconnected input and output communication channels between a computer program and its environment when it begins execution. The three input/output (I/O) connections are called standard input (stdin ...
. As
arguments
An argument is a statement or group of statements called premises intended to determine the degree of truth or acceptability of another statement called conclusion. Arguments can be studied from three main perspectives: the logical, the dialectic ...
, it takes two sets of characters (generally of the same length), and replaces occurrences of the characters in the first set with the corresponding elements from the second set. For example,
tr 'abcd' 'jkmn'
maps all characters ''a'' to ''j'', ''b'' to ''k'', ''c'' to ''m'', and ''d'' to ''n''.
The character set may be abbreviated by using character ranges. The previous example could be written:
tr 'a-d' 'jkmn'
In
POSIX
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...
-compliant versions of
tr, the set represented by a character range depends on the
locale's collating order, so it is safer to avoid character ranges in scripts that might be executed in a locale different from that in which they were written. Ranges can often be replaced with
POSIX
The Portable Operating System Interface (POSIX) is a family of standards specified by the IEEE Computer Society for maintaining compatibility between operating systems. POSIX defines both the system- and user-level application programming interf ...
character sets such as ''
alpha:'.
The ''
s'' flag causes
tr to compress sequences of identical adjacent characters in its output to a single token. For example,
tr -s '\n'
replaces sequences of one or more newline characters with a single newline.
The ''
d'' flag causes
tr to delete all tokens of the specified set of characters from its input. In this case, only a single character set argument is used. The following command removes carriage return characters.
tr -d '\r'
The ''
c'' flag indicates the complement of the first set of characters. The invocation
tr -cd '
alnum:
therefore removes all non-alphanumeric characters.
Implementations
The original version of
tr was written by
Douglas McIlroy
Malcolm Douglas McIlroy (born 1932) is a mathematician, engineer, and programmer. As of 2019 he is an Adjunct Professor of Computer Science at Dartmouth College.
McIlroy is best known for having originally proposed Unix pipelines and developed se ...
and was introduced in
Version 4 Unix
The term "Research Unix" refers to early versions of the Unix operating system for DEC PDP-7, PDP-11, VAX and Interdata 7/32 and 8/32 computers, developed in the Bell Labs Computing Sciences Research Center (CSRC).
History
The term ''Resear ...
.
The version of
tr bundled in
GNU
GNU () is an extensive collection of free software (383 packages as of January 2022), which can be used as an operating system or can be used in parts with other operating systems. The use of the completed GNU tools led to the family of operat ...
coreutils
The GNU Core Utilities or coreutils is a package of GNU software containing implementations for many of the basic tools, such as cat, ls, and rm, which are used on Unix-like operating systems.
In September 2002, the ''GNU coreutils'' were cr ...
was written by Jim Meyering. The command is available as a separate package for
Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...
as part of the
UnxUtils
UnxUtils is a collection of ports of common GNU Unix-like utilities to native Win32, with executables only depending on the Microsoft C- runtime msvcrt.dll. The collection was last updated externally on April 15, 2003, by Karl M. Syring. The mo ...
collection of
native
Native may refer to:
People
* Jus soli, citizenship by right of birth
* Indigenous peoples, peoples with a set of specific rights based on their historical ties to a particular territory
** Native Americans (disambiguation)
In arts and entert ...
Win32
The Windows API, informally WinAPI, is Microsoft's core set of application programming interfaces (APIs) available in the Microsoft Windows operating systems. The name Windows API collectively refers to several different platform implementations th ...
ports
A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as H ...
of common GNU Unix-like utilities. It is also available in the
OS-9
OS-9 is a family of real-time, process-based, multitasking, multi-user operating systems, developed in the 1980s, originally by Microware Systems Corporation for the Motorola 6809 microprocessor. It was purchased by Radisys Corp in 2001, and ...
shell. A
tr command is also part of
ASCII
ASCII ( ), abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Because of ...
's ''MSX-DOS2 Tools'' for
MSX-DOS
MSX-DOS is a discontinued disk operating system developed by Microsoft for the 8-bit home computer standard MSX, and is a cross between MS-DOS 1.25 and CP/M-80 2.
MSX-DOS
MSX-DOS and the extended BASIC with 3½-inch floppy disk support ...
version 2. The command has also been ported to the
IBM i
IBM i (the ''i'' standing for ''integrated'') is an operating system developed by IBM for IBM Power Systems. It was originally released in 1988 as OS/400, as the sole operating system of the IBM AS/400 line of systems. It was renamed to i5/OS in ...
operating system.
Most versions of
tr, including GNU
tr and classic Unix
tr, operate on single-byte characters and are not
Unicode
Unicode, formally The Unicode Standard,The formal version reference is is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...
compliant. An exception is the
Heirloom Toolchest implementation, which provides basic Unicode support.
Ruby
A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called sa ...
and
Perl
Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offici ...
also have an internal ''tr'' operator, which operates analogously.
Tcl
TCL or Tcl or TCLs may refer to:
Business
* TCL Technology, a Chinese consumer electronics and appliance company
**TCL Electronics, a subsidiary of TCL Technology
* Texas Collegiate League, a collegiate baseball league
* Trade Centre Limited ...
's ''string map'' command is more general in that it maps strings to strings while tr maps characters to characters.
See also
*
sed
sed ("stream editor") is a Unix utility that parses and transforms text, using a simple, compact programming language. It was developed from 1973 to 1974 by Lee E. McMahon of Bell Labs,
and is available today for most operating systems.
sed w ...
*
List of Unix commands
This is a list of Unix commands as specified by IEEE Std 1003.1-2008, which is part of the Single UNIX Specification (SUS). These commands can be found on Unix operating systems and most Unix-like operating systems.
List
See also
* List of G ...
*
GNU Core Utilities
The GNU Core Utilities or coreutils is a package of GNU software containing implementations for many of the basic tools, such as cat, ls, and rm, which are used on Unix-like operating systems.
In September 2002, the ''GNU coreutils'' were cr ...
References
External links
*
tr(1)– Unix 8th Edition manual page.
*
*
*
*
*
usage examples at examplenow.com
{{Core Utilities commands
Unix text processing utilities
Unix SUS2008 utilities
Plan 9 commands
Inferno (operating system) commands
IBM i Qshell commands