stringprep(3) libidn stringprep(3)

# [NAME](#NAME)

stringprep - API function

# [SYNOPSIS](#SYNOPSIS)

**#include <stringprep.h>**

**int stringprep(char * in, size\_t maxlen, Stringprep\_profile\_flags flags, const Stringprep\_profile * profile);**

# [ARGUMENTS](#ARGUMENTS)

[char * in](#char)

input/output array with string to prepare.

[size\_t maxlen](#size_t)

maximum length of input/output array.

[Stringprep\_profile\_flags flags](#Stringprep_profile_flags)

a **Stringprep\_profile\_flags** value, or 0.

[const Stringprep\_profile * profile](#const)

pointer to **Stringprep\_profile** to use.

# [DESCRIPTION](#DESCRIPTION)

Prepare the input zero terminated UTF-8 string according to the stringprep profile, and write back the result to the input string.

Note that you must convert strings entered in the systems locale into UTF-8 before using this function, see **stringprep\_locale\_to\_utf8()**.

Since the stringprep operation can expand the string, *maxlen* indicate how large the buffer holding the string is. This function will not read or write to characters outside that size.

The *flags* are one of **Stringprep\_profile\_flags** values, or 0.

The *profile* contain the **Stringprep\_profile** instructions to perform. Your application can define new profiles, possibly reusing the generic stringprep tables that always will be part of the library, or use one of the currently supported profiles.

Return value: Returns **STRINGPREP\_OK** iff successful, or an error code.

# [REPORTING BUGS](#REPORTING_BUGS)

Report bugs to <help-libidn@gnu.org>.  
General guidelines for reporting bugs: https://www.gnu.org/gethelp/  
GNU Libidn home page: https://www.gnu.org/software/libidn/

# [COPYRIGHT](#COPYRIGHT)

Copyright © 2002-2026 Simon Josefsson.  
Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

# [SEE ALSO](#SEE_ALSO)

The full documentation for **libidn** is maintained as a Texinfo manual. If the **info** and **libidn** programs are properly installed at your site, the command

**info libidn**

should give you access to the complete manual. As an alternative you may obtain the manual from:

**https://www.gnu.org/software/libidn/manual/**

1.44 libidn

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Document: stringprep(3) from libidn 1.44-r3 (Chainguard OS)
Source: https://gitlab.com/libidn/libidn