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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.1‐2017, 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.1‐2017, 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.1‐2017, 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.1‐2017, 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
1003.1-2017, Standard for Information Technology -- Portable Operating System Interface
(POSIX), The Open Group Base Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. 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.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page are most likely to have
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