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+Network Working Group                                    Y. Shafranovich
+Request for Comments: 4180                SolidMatrix Technologies, Inc.
+Category: Informational                                     October 2005
+
+
+   Common Format and MIME Type for Comma-Separated Values (CSV) Files
+
+Status of This Memo
+
+   This memo provides information for the Internet community.  It does
+   not specify an Internet standard of any kind.  Distribution of this
+   memo is unlimited.
+
+Copyright Notice
+
+   Copyright (C) The Internet Society (2005).
+
+Abstract
+
+   This RFC documents the format used for Comma-Separated Values (CSV)
+   files and registers the associated MIME type "text/csv".
+
+Table of Contents
+
+   1. Introduction ....................................................2
+   2. Definition of the CSV Format ....................................2
+   3. MIME Type Registration of text/csv ..............................4
+   4. IANA Considerations .............................................5
+   5. Security Considerations .........................................5
+   6. Acknowledgments .................................................6
+   7. References ......................................................6
+      7.1. Normative References .......................................6
+      7.2. Informative References .....................................6
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+Shafranovich                 Informational                      [Page 1]
+
+RFC 4180       Common Format and MIME Type for CSV Files    October 2005
+
+
+1.  Introduction
+
+   The comma separated values format (CSV) has been used for exchanging
+   and converting data between various spreadsheet programs for quite
+   some time.  Surprisingly, while this format is very common, it has
+   never been formally documented.  Additionally, while the IANA MIME
+   registration tree includes a registration for
+   "text/tab-separated-values" type, no MIME types have ever been
+   registered with IANA for CSV.  At the same time, various programs and
+   operating systems have begun to use different MIME types for this
+   format.  This RFC documents the format of comma separated values
+   (CSV) files and formally registers the "text/csv" MIME type for CSV
+   in accordance with RFC 2048 [1].
+
+2.  Definition of the CSV Format
+
+   While there are various specifications and implementations for the
+   CSV format (for ex. [4], [5], [6] and [7]), there is no formal
+   specification in existence, which allows for a wide variety of
+   interpretations of CSV files.  This section documents the format that
+   seems to be followed by most implementations:
+
+   1.  Each record is located on a separate line, delimited by a line
+       break (CRLF).  For example:
+
+       aaa,bbb,ccc CRLF
+       zzz,yyy,xxx CRLF
+
+   2.  The last record in the file may or may not have an ending line
+       break.  For example:
+
+       aaa,bbb,ccc CRLF
+       zzz,yyy,xxx
+
+   3.  There maybe an optional header line appearing as the first line
+       of the file with the same format as normal record lines.  This
+       header will contain names corresponding to the fields in the file
+       and should contain the same number of fields as the records in
+       the rest of the file (the presence or absence of the header line
+       should be indicated via the optional "header" parameter of this
+       MIME type).  For example:
+
+       field_name,field_name,field_name CRLF
+       aaa,bbb,ccc CRLF
+       zzz,yyy,xxx CRLF
+
+
+
+
+
+
+Shafranovich                 Informational                      [Page 2]
+
+RFC 4180       Common Format and MIME Type for CSV Files    October 2005
+
+
+   4.  Within the header and each record, there may be one or more
+       fields, separated by commas.  Each line should contain the same
+       number of fields throughout the file.  Spaces are considered part
+       of a field and should not be ignored.  The last field in the
+       record must not be followed by a comma.  For example:
+
+       aaa,bbb,ccc
+
+   5.  Each field may or may not be enclosed in double quotes (however
+       some programs, such as Microsoft Excel, do not use double quotes
+       at all).  If fields are not enclosed with double quotes, then
+       double quotes may not appear inside the fields.  For example:
+
+       "aaa","bbb","ccc" CRLF
+       zzz,yyy,xxx
+
+   6.  Fields containing line breaks (CRLF), double quotes, and commas
+       should be enclosed in double-quotes.  For example:
+
+       "aaa","b CRLF
+       bb","ccc" CRLF
+       zzz,yyy,xxx
+
+   7.  If double-quotes are used to enclose fields, then a double-quote
+       appearing inside a field must be escaped by preceding it with
+       another double quote.  For example:
+
+       "aaa","b""bb","ccc"
+
+   The ABNF grammar [2] appears as follows:
+
+   file = [header CRLF] record *(CRLF record) [CRLF]
+
+   header = name *(COMMA name)
+
+   record = field *(COMMA field)
+
+   name = field
+
+   field = (escaped / non-escaped)
+
+   escaped = DQUOTE *(TEXTDATA / COMMA / CR / LF / 2DQUOTE) DQUOTE
+
+   non-escaped = *TEXTDATA
+
+   COMMA = %x2C
+
+   CR = %x0D ;as per section 6.1 of RFC 2234 [2]
+
+
+
+Shafranovich                 Informational                      [Page 3]
+
+RFC 4180       Common Format and MIME Type for CSV Files    October 2005
+
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+   DQUOTE =  %x22 ;as per section 6.1 of RFC 2234 [2]
+
+   LF = %x0A ;as per section 6.1 of RFC 2234 [2]
+
+   CRLF = CR LF ;as per section 6.1 of RFC 2234 [2]
+
+   TEXTDATA =  %x20-21 / %x23-2B / %x2D-7E
+
+3.  MIME Type Registration of text/csv
+
+   This section provides the media-type registration application (as per
+   RFC 2048 [1].
+
+   To: ietf-types@iana.org
+
+   Subject: Registration of MIME media type text/csv
+
+   MIME media type name: text
+
+   MIME subtype name: csv
+
+   Required parameters: none
+
+   Optional parameters: charset, header
+
+      Common usage of CSV is US-ASCII, but other character sets defined
+      by IANA for the "text" tree may be used in conjunction with the
+      "charset" parameter.
+
+      The "header" parameter indicates the presence or absence of the
+      header line.  Valid values are "present" or "absent".
+      Implementors choosing not to use this parameter must make their
+      own decisions as to whether the header line is present or absent.
+
+   Encoding considerations:
+
+      As per section 4.1.1. of RFC 2046 [3], this media type uses CRLF
+      to denote line breaks.  However, implementors should be aware that
+      some implementations may use other values.
+
+   Security considerations:
+
+      CSV files contain passive text data that should not pose any
+      risks.  However, it is possible in theory that malicious binary
+      data may be included in order to exploit potential buffer overruns
+      in the program processing CSV data.  Additionally, private data
+      may be shared via this format (which of course applies to any text
+      data).
+
+
+
+Shafranovich                 Informational                      [Page 4]
+
+RFC 4180       Common Format and MIME Type for CSV Files    October 2005
+
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+   Interoperability considerations:
+
+      Due to lack of a single specification, there are considerable
+      differences among implementations.  Implementors should "be
+      conservative in what you do, be liberal in what you accept from
+      others" (RFC 793 [8]) when processing CSV files.  An attempt at a
+      common definition can be found in Section 2.
+
+      Implementations deciding not to use the optional "header"
+      parameter must make their own decision as to whether the header is
+      absent or present.
+
+   Published specification:
+
+      While numerous private specifications exist for various programs
+      and systems, there is no single "master" specification for this
+      format.  An attempt at a common definition can be found in Section
+      2.
+
+   Applications that use this media type:
+
+      Spreadsheet programs and various data conversion utilities
+
+   Additional information:
+
+      Magic number(s): none
+
+      File extension(s): CSV
+
+      Macintosh File Type Code(s): TEXT
+
+   Person & email address to contact for further information:
+
+      Yakov Shafranovich <ietf@shaftek.org>
+
+   Intended usage: COMMON
+
+   Author/Change controller: IESG
+
+4.  IANA Considerations
+
+   The IANA has registered the MIME type "text/csv" using the
+   application provided in Section 3 of this document.
+
+5.  Security Considerations
+
+   See discussion above in section 3.
+
+
+
+
+Shafranovich                 Informational                      [Page 5]
+
+RFC 4180       Common Format and MIME Type for CSV Files    October 2005
+
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+6.  Acknowledgments
+
+   The author would like to thank Dave Crocker, Martin Duerst, Joel M.
+   Halpern, Clyde Ingram, Graham Klyne, Bruce Lilly, Chris Lilley, and
+   members of the IESG for their helpful suggestions.  A special word of
+   thanks goes to Dave for helping with the ABNF grammar.
+
+   The author would also like to thank Henrik Lefkowetz, Marshall Rose,
+   and the folks at xml.resource.org for providing many of the tools
+   used for preparing RFCs and Internet drafts.
+
+   A special thank you goes to L.T.S.
+
+7.  References
+
+7.1.  Normative References
+
+   [1]  Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet
+        Mail Extensions (MIME) Part Four: Registration Procedures", BCP
+        13, RFC 2048, November 1996.
+
+   [2]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
+        Specifications: ABNF", RFC 2234, November 1997.
+
+   [3]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
+        Extensions (MIME) Part Two: Media Types", RFC 2046, November
+        1996.
+
+7.2.  Informative References
+
+   [4]  Repici, J., "HOW-TO: The Comma Separated Value (CSV) File
+        Format", 2004,
+        <http://www.creativyst.com/Doc/Articles/CSV/CSV01.htm>.
+
+   [5]  Edoceo, Inc., "CSV Standard File Format", 2004,
+        <http://www.edoceo.com/utilis/csv-file-format.php>.
+
+   [6]  Rodger, R. and O. Shanaghy, "Documentation for Ricebridge CSV
+        Manager", February 2005,
+        <http://www.ricebridge.com/products/csvman/reference.htm>.
+
+   [7]  Raymond, E., "The Art of Unix Programming, Chapter 5", September
+        2003,
+        <http://www.catb.org/~esr/writings/taoup/html/ch05s02.html>.
+
+   [8]  Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
+        September 1981.
+
+
+
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+Shafranovich                 Informational                      [Page 6]
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+RFC 4180       Common Format and MIME Type for CSV Files    October 2005
+
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+Author's Address
+
+   Yakov Shafranovich
+   SolidMatrix Technologies, Inc.
+
+   EMail: ietf@shaftek.org
+   URI:   http://www.shaftek.org
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+Shafranovich                 Informational                      [Page 7]
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+RFC 4180       Common Format and MIME Type for CSV Files    October 2005
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+Full Copyright Statement
+
+   Copyright (C) The Internet Society (2005).
+
+   This document is subject to the rights, licenses and restrictions
+   contained in BCP 78, and except as set forth therein, the authors
+   retain all their rights.
+
+   This document and the information contained herein are provided on an
+   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
+   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
+   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
+   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
+   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
+   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
+
+Intellectual Property
+
+   The IETF takes no position regarding the validity or scope of any
+   Intellectual Property Rights or other rights that might be claimed to
+   pertain to the implementation or use of the technology described in
+   this document or the extent to which any license under such rights
+   might or might not be available; nor does it represent that it has
+   made any independent effort to identify any such rights.  Information
+   on the procedures with respect to rights in RFC documents can be
+   found in BCP 78 and BCP 79.
+
+   Copies of IPR disclosures made to the IETF Secretariat and any
+   assurances of licenses to be made available, or the result of an
+   attempt made to obtain a general license or permission for the use of
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+   specification can be obtained from the IETF on-line IPR repository at
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+
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+   this standard.  Please address the information to the IETF at ietf-
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+
+Acknowledgement
+
+   Funding for the RFC Editor function is currently provided by the
+   Internet Society.
+
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+Shafranovich                 Informational                      [Page 8]
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