---
name: "iconv_open"
section: "3p"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/iconv_open/3p"
---

# iconv\_open(3p)

codeset conversion allocation function

## 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\_open — codeset conversion allocation function

## SYNOPSIS

```
#include <iconv.h>
```

iconv\_t iconv\_open(const char \**tocode*, const char \**fromcode*);

## DESCRIPTION

The *iconv\_open*() function shall return a conversion descriptor that describes a conversion from the codeset specified by the string pointed to by the *fromcode* argument to the codeset specified by the string pointed to by the *tocode* argument. For state-dependent encodings, the conversion descriptor shall be in a codeset-dependent initial shift state, ready for immediate use with *iconv*().

Settings of *fromcode* and *tocode* and their permitted combinations are implementation-defined.

A conversion descriptor shall remain valid until it is closed by *iconv\_close*() or an implicit close.

If a file descriptor is used to implement conversion descriptors, the FD\_CLOEXEC flag shall be set; see *\<fcntl.h\>*.

## RETURN VALUE

Upon successful completion, *iconv\_open*() shall return a conversion descriptor for use on subsequent calls to *iconv*(). Otherwise, *iconv\_open*() shall return (**iconv\_t**)-1 and set *errno* to indicate the error.

## ERRORS

The *iconv\_open*() function may fail if:

- **EMFILE**

  All file descriptors available to the process are currently open.

- **ENFILE**

  Too many files are currently open in the system.

- **ENOMEM**

  Insufficient storage space is available.

- **EINVAL**

  The conversion specified by *fromcode* and *tocode* is not supported by the implementation.

*The following sections are informative.*

## EXAMPLES

None.

## APPLICATION USAGE

Some implementations of *iconv\_open*() use *malloc*() to allocate space for internal buffer areas. The *iconv\_open*() function may fail if there is insufficient storage space to accommodate these buffers.

Conforming applications must assume that conversion descriptors are not valid after a call to one of the *exec* functions.

Application developers should consult the system documentation to determine the supported codesets and their naming schemes.

## RATIONALE

None.

## FUTURE DIRECTIONS

None.

## SEE ALSO

*iconv()*, *iconv\_close()*

The Base Definitions volume of POSIX.1‐2017, ***\<fcntl.h\>***, ***\<iconv.h\>***

## 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 been introduced during the conversion of the source files to man page format. To report such errors, see https://www.kernel.org/doc/man-pages/reporting\_bugs.html .