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PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface
may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface
may not be implemented on Linux.
NAME
iconv — codeset conversion
SYNOPSIS
iconv [−cs] −f frommap −t tomap [file...]
iconv −f fromcode [−cs] [−t tocode] [file...]
iconv −t tocode [−cs] [−f fromcode] [file...]
iconv −l
DESCRIPTION
The iconv utility shall convert the encoding of characters in file from one codeset to another and write
the results to standard output.
When the options indicate that charmap files are used to specify the codesets (see OPTIONS), the codeset
conversion shall be accomplished by performing a logical join on the symbolic character names in the two
charmaps. The implementation need not support the use of charmap files for codeset conversion unless the
POSIX2_LOCALEDEF symbol is defined on the system.
OPTIONS
The iconv utility shall conform to the Base Definitions volume of POSIX.1‐2008, Section 12.2, Utility
Syntax Guidelines.
The following options shall be supported:
−c Omit any characters that are invalid in the codeset of the input file from the output. When −c
is not used, the results of encountering invalid characters in the input stream (either those
that are not characters in the codeset of the input file or that have no corresponding
character in the codeset of the output file) shall be specified in the system documentation.
The presence or absence of −c shall not affect the exit status of iconv.
−f fromcodeset
Identify the codeset of the input file. The implementation shall recognize the following two
forms of the fromcodeset option-argument:
fromcode The fromcode option-argument must not contain a <slash> character. It shall be
interpreted as the name of one of the codeset descriptions provided by the
implementation in an unspecified format. Valid values of fromcode are implementation-
defined.
frommap The frommap option-argument must contain a <slash> character. It shall be interpreted
as the pathname of a charmap file as defined in the Base Definitions volume of
POSIX.1‐2008, Section 6.4, Character Set Description File. If the pathname does not
represent a valid, readable charmap file, the results are undefined.
If this option is omitted, the codeset of the current locale shall be used.
−l Write all supported fromcode and tocode values to standard output in an unspecified format.
−s Suppress any messages written to standard error concerning invalid characters. When −s is not
used, the results of encountering invalid characters in the input stream (either those that are
not valid characters in the codeset of the input file or that have no corresponding character
in the codeset of the output file) shall be specified in the system documentation. The presence
or absence of −s shall not affect the exit status of iconv.
−t tocodeset
Identify the codeset to be used for the output file. The implementation shall recognize the
following two forms of the tocodeset option-argument:
tocode The semantics shall be equivalent to the −f fromcode option.
tomap The semantics shall be equivalent to the −f frommap option.
If this option is omitted, the codeset of the current locale shall be used.
If either −f or −t represents a charmap file, but the other does not (or is omitted), or both −f and −t
are omitted, the results are undefined.
OPERANDS
The following operand shall be supported:
file A pathname of an input file. If no file operands are specified, or if a file operand is '−',
the standard input shall be used.
STDIN
The standard input shall be used only if no file operands are specified, or if a file operand is '−'.
INPUT FILES
The input file shall be a text file.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of iconv:
LANG Provide a default value for the internationalization variables that are unset or null. (See the
Base Definitions volume of POSIX.1‐2008, Section 8.2, Internationalization Variables for the
precedence of internationalization variables used to determine the values of locale
categories.)
LC_ALL If set to a non-empty string value, override the values of all the other internationalization
variables.
LC_CTYPE Determine the locale for the interpretation of sequences of bytes of text data as characters
(for example, single-byte as opposed to multi-byte characters in arguments). During translation
of the file, this variable is superseded by the use of the fromcode option-argument.
LC_MESSAGES
Determine the locale that should be used to affect the format and contents of diagnostic
messages written to standard error.
NLSPATH Determine the location of message catalogs for the processing of LC_MESSAGES.
ASYNCHRONOUS EVENTS
Default.
STDOUT
When the −l option is used, the standard output shall contain all supported fromcode and tocode values,
written in an unspecified format.
When the −l option is not used, the standard output shall contain the sequence of characters read from
the input files, translated to the specified codeset. Nothing else shall be written to the standard
output.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
The following exit values shall be returned:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
The user must ensure that both charmap files use the same symbolic names for characters the two codesets
have in common.
EXAMPLES
The following example converts the contents of file mail.x400 from the ISO/IEC 6937:2001 standard codeset
to the ISO/IEC 8859‐1:1998 standard codeset, and stores the results in file mail.local:
iconv −f IS6937 −t IS8859 mail.x400 > mail.local
RATIONALE
The iconv utility can be used portably only when the user provides two charmap files as option-arguments.
This is because a single charmap provided by the user cannot reliably be joined with the names in a
system-provided character set description. The valid values for fromcode and tocode are implementation-
defined and do not have to have any relation to the charmap mechanisms. As an aid to interactive users,
the −l option was adopted from the Plan 9 operating system. It writes information concerning these
implementation-defined values. The format is unspecified because there are many possible useful formats
that could be chosen, such as a matrix of valid combinations of fromcode and tocode. The −l option is
not intended for shell script usage; conforming applications will have to use charmaps.
The iconv utility may support the conversion between ASCII and EBCDIC-based encodings, but is not
required to do so. In an XSI-compliant implementation, the dd utility is the only method guaranteed to
support conversion between these two character sets.
FUTURE DIRECTIONS
None.
SEE ALSO
dd, gencat
The Base Definitions volume of POSIX.1‐2008, Section 6.4, Character Set Description File, Chapter 8,
Environment Variables, Section 12.2, Utility Syntax Guidelines
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition,
Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electrical and Electronics Engineers, Inc
and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the event
of any discrepancy between this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at
http://www.unix.org/online.html .
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