WordNet

the 12th letter of the Roman alphabet (同)l

PrepTutorEJDIC

lira(イタリアの貨幣単位リラ)
low frequency

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/09/05 17:22:30」(JST)

wiki en

For other uses, see New Line (disambiguation).

Text file created with gedit and viewed with a hex editor. Besides the text objects, there are only EOL markers with the hexadecimal value 0A.

In computing a newline,^[1] also known as a line break or end-of-line (EOL) marker, or simply break, is a special character or sequence of characters signifying the end of a line of text. The name comes from the fact that the next character after the newline will appear on a new line—that is, on the next line below the text immediately preceding the newline. The actual codes representing a newline vary across operating systems, which can be a problem when exchanging text files between systems with different newline representations.

There is also some confusion whether newlines terminate or separate lines. If a newline is considered a separator, there will be no newline after the last line of a file. Some programs have problems processing the last line of a file if it is not newline terminated. Conversely, programs that expect newline to be used as a separator will interpret a final newline as starting a new (empty) line.

In text intended primarily to be read by humans using software which implements the word wrap feature, a newline character typically only needs to be stored if a line break is required independent of whether the next word would fit on the same line, such as between paragraphs and in vertical lists.

Representations[edit source | edit]

Software applications and operating systems usually represent a newline with one or two control characters:

Systems based on ASCII or a compatible character set use either LF (Line feed, '\n', 0x0A, 10 in decimal) or CR (Carriage return, '\r', 0x0D, 13 in decimal) individually, or CR followed by LF (CR+LF, '\r\n', 0x0D0A). These characters are based on printer commands: The line feed indicated that one line of paper should feed out of the printer thus instructed the printer to advance the paper one line, and a carriage return indicated that the printer carriage should return to the beginning of the current line. Some rare systems, such as QNX before version 4, used the ASCII RS (record separator, 0x1E, 30 in decimal) character as the newline character.
- LF: Multics, Unix and Unix-like systems (GNU/Linux, OS X, FreeBSD, AIX, Xenix, etc.), BeOS, Amiga, RISC OS and others.
- CR+LF: Microsoft Windows, DEC TOPS-10, RT-11 and most other early non-Unix and non-IBM OSes, CP/M, MP/M, DOS (MS-DOS, PC DOS, etc.), Atari TOS, OS/2, Symbian OS, Palm OS, Amstrad CPC
- LF+CR: Acorn BBC and RISC OS spooled text output.
- CR: Commodore 8-bit machines, Acorn BBC, ZX Spectrum, TRS-80, Apple II family, Mac OS up to version 9 and OS-9
- RS: QNX pre-POSIX implementation.
EBCDIC systems—mainly IBM mainframe systems, including z/OS (OS/390) and i5/OS (OS/400)—use NL (New Line, 0x15)^[2] as the character combining the functions of line-feed and carriage-return. The equivalent UNICODE character is called NEL (Next Line). Note that EBCDIC also has control characters called CR and LF, but the numerical value of LF (0x25) differs from the one used by ASCII (0x0A). Additionally, there are some EBCDIC variants that also use NL but assign a different numeric code to the character.
Operating systems for the CDC 6000 series defined a newline as two or more zero-valued six-bit characters at the end of a 60-bit word. Some configurations also defined a zero-valued character as a colon character, with the result that multiple colons could be interpreted as a newline depending on position.
ZX80 and ZX81, home computers from Sinclair Research Ltd used a specific non-ASCII character set with code NEWLINE (0x76, 118 decimal) as the newline character.
OpenVMS uses a record-based file system, which stores text files as one record per line. In most file formats, no line terminators are actually stored, but the Record Management Services facility can transparently add a terminator to each line when it is retrieved by an application. The records themselves could contain the same line terminator characters, which could either be considered a feature or a nuisance depending on the application.
Fixed line length was used by some early mainframe operating systems. In such a system, an implicit end-of-line was assumed every 72 or 80 characters, for example. No newline character was stored. If a file was imported from the outside world, lines shorter than the line length had to be padded with spaces, while lines longer than the line length had to be truncated. This mimicked the use of punched cards, on which each line was stored on a separate card, usually with 80 columns on each card, often with sequence numbers in columns 73-80. Many of these systems added a carriage control character to the start of the next record; this could indicate if the next record was a continuation of the line started by the previous record, or a new line, or should overprint the previous line (similar to a CR). Often this was a normal printing character such as '#' that thus could not be used as the first character in a line. Some early line printers interpreted these characters directly in the records sent to them.

Most textual Internet protocols (including HTTP, SMTP, FTP, IRC and many others) mandate the use of ASCII CR+LF ('\r\n', 0x0D 0x0A) on the protocol level, but recommend that tolerant applications recognize lone LF ('\n', 0x0A) as well. In practice, there are many applications that erroneously use the C newline character '\n' instead (see section Newline in programming languages below). This leads to problems when trying to communicate with systems adhering to a stricter interpretation of the standards; one such system is the qmail MTA that actively refuses to accept messages from systems that send bare LF instead of the required CR+LF.^[3]

FTP has a feature to transform newlines between CR+LF and the native encoding of the system (e.g., LF only) when transferring text files. This must not be used on binary files. Often binary files and text files are recognised by checking their filename extension; most command line FTP clients have an explicit command to switch between binary vs. text mode transfers.

Unicode[edit source | edit]

The Unicode standard defines a large number of characters that conforming applications should recognize as line terminators:^[4]

LF:    Line Feed, U+000A
VT:    Vertical Tab, U+000B
FF:    Form Feed, U+000C
CR:    Carriage Return, U+000D
CR+LF: CR (U+000D) followed by LF (U+000A)
NEL:   Next Line, U+0085
LS:    Line Separator, U+2028
PS:    Paragraph Separator, U+2029

This may seem overly complicated compared to an approach such as converting all line terminators to a single character, for example LF. However, Unicode was designed to preserve all information when converting a text file from any existing encoding to Unicode and back. Therefore, Unicode should contain characters included in existing encodings. NEL is included in EBCDIC with code (0x15). NEL is also a control character in the C1 control set.^[5] As such, it is defined by ECMA 48,^[6] and recognized by encodings compliant with ISO-2022 (which is equivalent to ECMA 35).^[7] C1 control set is also compatible with ISO-8859-1^{[citation needed]}. The approach taken in the Unicode standard allows round-trip transformation to be information-preserving while still enabling applications to recognize all possible types of line terminators.

Recognizing and using the newline codes greater than 0x7F is not often done. They are multiple bytes in UTF-8 and the code for NEL has been used as the ellipsis ('…') character in Windows-1252. For instance:

YAML^[8] no longer recognizes them as special, in order to be compatible with JSON.
ECMAScript^[9] accepts LS and PS as line breaks, but considers U+0085 (NEL) white space, not a line break.
Microsoft Windows 2000 does not treat any of NEL, LS or PS as line-break in the default text editor Notepad
In Linux, a popular editor "gedit" treats LS and PS as newlines but does not for NEL.

History[edit source | edit]

ASCII was developed simultaneously by the ISO and the ASA, the predecessor organization to ANSI. During the period of 1963–1968, the ISO draft standards supported the use of either CR+LF or LF alone as a newline, while the ASA drafts supported only CR+LF.

The sequence CR+LF was in common use on many early computer systems that had adopted Teletype machines, typically a Teletype Model 33 ASR, as a console device, because this sequence was required to position those printers at the start of a new line. On these systems, text was often routinely composed to be compatible with these printers, since the concept of device drivers hiding such hardware details from the application was not yet well developed; applications had to talk directly to the Teletype machine and follow its conventions. In particular, this explains the names of the control characters, which signify the actions of an ordinary mechanical typewriter of the times: "Line Feed" is the action to switch to a new line, carried out by the paper feed mechanism of the typewriter carriage, and "Carriage Return" is the action to position the typing device at the beginning of the line, carried out by the sliding movement of the carriage.

Most minicomputer systems from DEC used this convention. CP/M used it as well, to print on the same terminals that minicomputers used. From there MS-DOS (1981) adopted CP/M's CR+LF in order to be compatible, and this convention was inherited by Microsoft's later Windows operating system.

The separation of the two functions concealed the fact that the print head could not return from the far right to the beginning of the next line in one-character time. That is why the sequence was always sent with the CR first. In fact, it was often necessary to send extra characters (extraneous CRs or NULs, which are ignored) to give the print head time to move to the left margin. Even many early video displays required multiple character times to scroll the display.

The Multics operating system began development in 1964 and used LF alone as its newline. Multics used a device driver to translate this character to whatever sequence a printer needed (including extra padding characters), and the single byte was much more convenient for programming. The seemingly more obvious choice of CR was not used, as a plain CR provided the useful function of overprinting one line with another to create Boldface and Strikethrough effects, and thus it was useful to not translate it. Unix followed the Multics practice, and later systems followed Unix.

In programming languages[edit source | edit]

To facilitate the creation of portable programs, programming languages provide some abstractions to deal with the different types of newline sequences used in different environments.

The C programming language provides the escape sequences '\n' (newline) and '\r' (carriage return). However, these are not required to be equivalent to the ASCII LF and CR control characters. The C standard only guarantees two things:

Each of these escape sequences maps to a unique implementation-defined number that can be stored in a single char value.
When writing a file in text mode, '\n' is transparently translated to the native newline sequence used by the system, which may be longer than one character. When reading in text mode, the native newline sequence is translated back to '\n'. In binary mode, no translation is performed, and the internal representation produced by '\n' is output directly.

On Unix platforms, where C originated, the native newline sequence is ASCII LF (0x0A), so '\n' was simply defined to be that value. With the internal and external representation being identical, the translation performed in text mode is a no-op, and text mode and binary mode behave the same. This has caused many programmers who developed their software on Unix systems simply to ignore the distinction completely, resulting in code that is not portable to different platforms.

The C library function fgets() is best avoided in binary mode because any file not written with the UNIX newline convention will be misread. Also, in text mode, any file not written with the system's native newline sequence (such as a file created on a UNIX system, then copied to a Windows system) will be misread as well.

Another common problem is the use of '\n' when communicating using an Internet protocol that mandates the use of ASCII CR+LF for ending lines. Writing '\n' to a text mode stream works correctly on Windows systems, but produces only LF on Unix, and something completely different on more exotic systems. Using "\r\n" in binary mode is slightly better.

Many languages, such as C++, Perl,^[10] and Haskell provide the same interpretation of '\n' as C.

Java, PHP^[11] and Python^[12] provide the '\r\n' sequence (for ASCII CR+LF). In contrast to C, these are guaranteed to represent the values U+000D and U+000A, respectively.

The Java I/O libraries do not transparently translate these into platform-dependent newline sequences on input or output. Instead, they provide functions for writing a full line that automatically add the native newline sequence, and functions for reading lines that accept any of CR, LF, or CR+LF as a line terminator (see BufferedReader.readLine()). The System.getProperty() method can be used to retrieve the underlying line separator.

Example:

   String eol = System.getProperty( "line.separator" );
   String lineColor = "Color: Red" + eol;

Python permits "Universal Newline Support" when opening a file for reading, when importing modules, and when executing a file.^[13]

Some languages have created special variables, constants, and subroutines to facilitate newlines during program execution.

In PHP, to avoid portability problems, newline sequences should be issued using the PHP_EOL constant.^[14]

Common problems[edit source | edit]

The different newline conventions often cause text files that have been transferred between systems of different types to be displayed incorrectly. For example, files originating on Unix or Apple Macintosh systems may appear as a single long line on some Windows programs. Conversely, when viewing a file originating from a Windows computer on a Unix system, the extra CR may be displayed as ^M or <cr> at the end of each line or as a second line break.

The problem can be hard to spot if some programs handle the foreign newlines properly while others do not. For example, a compiler may fail with obscure syntax errors even though the source file looks correct when displayed on the console or in an editor. On a Unix system, the command cat -v myfile.txt will send the file to stdout (normally the terminal) and make the ^M visible, which can be useful for debugging. Modern text editors generally recognize all flavours of CR / LF newlines and allow the user to convert between the different standards. Web browsers are usually also capable of displaying text files and websites which use different types of newlines.

The File Transfer Protocol can automatically convert newlines in files being transferred between systems with different newline representations when the transfer is done in "ASCII mode". However, transferring binary files in this mode usually has disastrous results: any occurrence of the newline byte sequence—which does not have line terminator semantics in this context, but is just part of a normal sequence of bytes—will be translated to whatever newline representation the other system uses, effectively corrupting the file. Such a file is considered 'cooked'.^[15] FTP clients often employ some heuristics (for example, inspection of filename extensions) to automatically select either binary or ASCII mode, but in the end it is up to the user to make sure his or her files are transferred in the correct mode. If there is any doubt as to the correct mode, binary mode should be used, as then no files will be altered by FTP, though they may display incorrectly.

Conversion utilities[edit source | edit]

Text editors are often used for converting a text file between different newline formats; most modern editors can read and write files using at least the different ASCII CR/LF conventions. The standard Windows editor Notepad is not one of them (although Wordpad and the MS-DOS Editor are).

Editors are often unsuitable for converting larger files. For larger files (on Windows NT/2000/XP) the following command is often used:

 >TYPE unix_file | FIND "" /V > dos_file

On many Unix systems, the dos2unix (sometimes named fromdos or d2u) and unix2dos (sometimes named todos or u2d) utilities are used to translate between ASCII CR+LF (DOS/Windows) and LF (Unix) newlines. Different versions of these commands vary slightly in their syntax. However, the tr command is available on virtually every Unix-like system and is used to perform arbitrary replacement operations on single characters. A DOS/Windows text file can be converted to Unix format by simply removing all ASCII CR characters with

$ tr -d '\r' < inputfile > outputfile

or, if the text has only CR newlines, by converting all CR newlines to LF with

$ tr '\r' '\n' < inputfile > outputfile

The same tasks are sometimes performed with awk, sed, tr or in Perl if the platform has a Perl interpreter:

$ awk '{sub("$","\r\n"); printf("%s",$0);}' inputfile > outputfile  # UNIX to DOS  (adding CRs on Linux and BSD based OS that haven't GNU extensions)
$ awk '{gsub("\r",""); print;}' inputfile > outputfile              # DOS to UNIX  (removing CRs on Linux and BSD based OS that haven't GNU extensions)
$ sed -e 's/$/\r/' inputfile > outputfile              # UNIX to DOS  (adding CRs on Linux based OS that use GNU extensions)
$ sed -e 's/\r$//' inputfile > outputfile              # DOS  to UNIX (removing CRs on Linux based OS that use GNU extensions)
$ cat inputfile | tr -d "\r" > outputfile              # DOS  to UNIX (removing CRs using tr(1). Not Unicode compliant.)
$ perl -pe 's/\r?\n|\r/\r\n/g' inputfile > outputfile  # Convert to DOS
$ perl -pe 's/\r?\n|\r/\n/g'   inputfile > outputfile  # Convert to UNIX
$ perl -pe 's/\r?\n|\r/\r/g'   inputfile > outputfile  # Convert to old Mac

To identify what type of line breaks a text file contains, the file command can be used. Moreover, the editor Vim can be convenient to make a file compatible with the Windows notepad text editor. For example:

 $ file myfile.txt
 myfile.txt: ASCII English text
 $ vim myfile.txt

within vim

 :set fileformat=dos
 :wq

 $ file myfile.txt
 myfile.txt: ASCII English text, with CRLF line terminators

The following grep commands echo the filename (in this case myfile.txt) to the command line if the file is of the specified style:

$ grep -PL $'\r\n' myfile.txt # show UNIX style file (LF terminated)
$ grep -Pl $'\r\n' myfile.txt # show DOS style file (CRLF terminated)

For Debian-based systems, these commands are used:

$ egrep -L $'\r\n' myfile.txt # show UNIX style file (LF terminated)
$ egrep -l $'\r\n' myfile.txt # show DOS style file (CRLF terminated)

The above grep commands work under Unix systems or in Cygwin under Windows. Note that these commands make some assumptions about the kinds of files that exist on the system (specifically it's assuming only UNIX and DOS-style files—no Mac OS 9-style files).

This technique is often combined with find to list files recursively. For instance, the following command checks all "regular files" (e.g. it will exclude directories, symbolic links, etc.) to find all UNIX-style files in a directory tree, starting from the current directory (.), and saves the results in file unix_files.txt, overwriting it if the file already exists:

$ find . -type f -exec grep -PL '\r\n' {} \; > unix_files.txt

This example will find C files and convert them to LF style line endings:

$ find -name '*.[ch]' -exec fromdos {} \;

The file command also detects the type of EOL used:

$ file myfile.txt
myfile.txt: ASCII text, with CRLF line terminators

Other tools permit the user to visualise the EOL characters:

$ od -a myfile.txt
$ cat -e myfile.txt
$ hexdump -c myfile.txt

dos2unix, unix2dos, mac2unix, unix2mac, mac2dos, dos2mac can perform conversions. The flip^[16] command is often used.

In Popular Culture[edit source | edit]

In the sci-fi 2010 film Tron Legacy, the End of Line Club borrowed the phrase for the tile of their club from this command. The End of Line Club in the film is on the final floor in a downtown skyscraper, and plays a significant part in the film. The film focuses on a virtual reality alternate universe inside of a computer, with many references made to the functions and processes of computing.

In the re-imagined Battlestar Galactica (2004 TV series) the Cylon protagonists' mother-ships, known as Basestars, each contain another type of Cylon, an autonomous bio-mechanical being known as a Hybrid. The Hybrids act as a central computer inside the Basestars, and are mainly characterized by their seemingly random but ultimately profound ramblings and utterances. They often complete their ideas or technical reports with the phrase, 'end of line'.

References[edit source | edit]

^ The origin of the older computer term "CRLF" - which redirects to this Newline article - or "Carriage Return [and] Line Feed", derives from standard manual typewriter design, whereby at the end of a line of text the typist pushes a lever at the left end of the carriage to return it to position for beginning the next line. In so doing, a mechanism also rolls the typewriter's platen by one line, advancing ("feeding") the paper to the correct position.
^ IBM System/360 Referencce Data Card, Publication GX20-1703, IBM Data Processing Division, White Plains, NY
^ cr.yp.to
^ UTR #13: Unicode Newline Guidelines
^ http://www.itscj.ipsj.or.jp/ISO-IR/077.pdf
^ http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-048.pdf Control Functions for Coded Character Sets Juin 1991
^ http://www.ecma-international.org/publications/files/ECMA-ST/Ecma-035.pdf Character Code Structure and Extension Techniques 1971. Three further editions in 1980, 1982 and 1985, Décembre 1994
^ YAML Ain't Markup Language (YAML™) Version 1.2
^ "ECMAScript Language Specification 5th edition". ECMA International. December 2009. p. 15. Retrieved 4 April 2010.
^ binmode - perldoc.perl.org
^ PHP: Strings - Manual
^ Lexical analysis – Python v3.0.1 documentation
^ What's new in Python 2.3
^ PHP: Predefined Constants
^ "Thoughts on Cooked MP3's". Retrieved 15 September 2012.
^ ASCII text converstion between UNIX, Macintosh, MS-DOS

External links[edit source | edit]

The Unicode reference, see paragraph 5.8 in Chapter 5 of the Unicode 4.0 standard (PDF)
"The End-of-Line Story"
The [NEL] Newline Character
The End of Line Puzzle
"Understanding Newlines" on O'Reilly-Net - an article by Xavier Noria.

English Journal

In vitro effect of low-fluoride toothpastes containing sodium trimetaphosphate on enamel erosion.

Cruz NV1, Pessan JP1, Manarelli MM1, Souza MD1, Delbem AC2.
Archives of oral biology.Arch Oral Biol.2015 Sep;60(9):1231-6. doi: 10.1016/j.archoralbio.2015.05.010. Epub 2015 Jun 6.
OBJECTIVE: To evaluate the effect of a low-fluoride dentifrice (LFD) containing sodium trimetaphosphate (TMP) on enamel erosion in vitro.DESIGN: Bovine enamel blocks (n=144) were selected by surface hardness (SH) and subjected to erosive challenges, in two sets of experiments for 2 and 5 days. Block
PMID 26092765

Rapid and Sensitive Detection of Vibrio alginolyticus by Loop-Mediated Isothermal Amplification Combined with a Lateral Flow Dipstick Targeted to the rpoX Gene.

Plaon S1, Longyant S, Sithigorngul P, Chaivisuthangkura P.
Journal of aquatic animal health.J Aquat Anim Health.2015 Sep;27(3):156-63. doi: 10.1080/08997659.2015.1037468.
Vibrio alginolyticus is a major bacterial pathogen causing disease in marine animals. The present study aimed to develop a loop-mediated isothermal amplification (LAMP) coupled with a lateral flow dipstick (LFD) for rapid and simple visual detection of V. alginolyticus-specific amplicons. The biotin
PMID 26220075

Development of an Immunochromatographic Lateral Flow Device for Rapid Detection of Helicobacter pylori Stool Antigen.

Lin Z1, Cheng S2, Yan Q3, Liu X2, Zheng W2, Hu X4, Li J4, Zhang J5, Xiang T3, Zheng J6, Zhang J7.
Clinical biochemistry.Clin Biochem.2015 Aug 6. pii: S0009-9120(15)00384-7. doi: 10.1016/j.clinbiochem.2015.08.004. [Epub ahead of print]
OBJECTIVE: Helicobacter pylori stool antigen (HpSA) test is a convenient and reliable non-invasive diagnosis for Helicobacter pylori (H. pylori) infection. The aim of this study is to develop an immunochromatographic testing device for rapid detection of HpSA among Chinese patients.DESIGN AND METHOD
PMID 26256542

Japanese Journal

P3-61-4 当院で出生したLFD(light for date)児の検討(Group 163 FGR,胎児その他,一般演題,公益社団法人日本産科婦人科学会第67回学術講演会)

日本産科婦人科學會雜誌 67(2), 988, 2015-02-01
NAID 110009942037

測位データ変動における複雑性解析のための一方法 : 局所的フラクタル次元の活用法(測位・航法,レーダ及び一般)

電子情報通信学会技術研究報告. SANE, 宇宙・航行エレクトロニクス 114(397), 59-64, 2015-01-15
NAID 110010001990

C301 マクロ的気象変動におけるLFDを用いた複雑性観測のための一方法(観測手法,口頭発表)

大会講演予講集 106, 394, 2014-09-30
NAID 110009897980

Related Pictures

Art Dudley has posted a review of the LFD lfd audio mistral lfd audio mistral LFD-880 8インチフロッピー Samsung LFD MD55, 55 Samsung Launches LED Large Format Display Samsung Lfd | Technology News and Product