---
name: "strxfrm_l"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/strxfrm"
---

# strxfrm\_l(3)

transform a string under locale

Part of [strxfrm(3)](/strxfrm/3.md).

## NAME

**strxfrm** – transform a string under locale

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<string.h\>**

*size\_t*\

**strxfrm**(*char \* restrict dst*, *const char \* restrict src*, *size\_t n*);

*size\_t*\

**strxfrm\_l**(*char \* restrict dst*, *const char \*restrict src*, *size\_t n*, *locale\_t loc*);

## DESCRIPTION

The **strxfrm**() function transforms a null-terminated string pointed to by *src* according to the current locale collation if any, then copies the transformed string into *dst*. Not more than *n* characters are copied into *dst*, including the terminating null character added. If *n* is set to 0 (it helps to determine an actual size needed for transformation), *dst* is permitted to be a NULL pointer.

Comparing two strings using **strcmp**() after **strxfrm**() is equal to comparing two original strings with **strcoll**().

**strxfrm\_l**() does the same, however takes an explicit locale rather than the global locale.

## RETURN VALUES

Upon successful completion, **strxfrm**() and **strxfrm\_l**() return the length of the transformed string not including the terminating null character. If this value is *n* or more, the contents of *dst* are indeterminate.

## SEE ALSO

[setlocale(3)](/setlocale/3.md), [strcmp(3)](/strcmp/3.md), [strcoll(3)](/strcoll/3.md), [wcsxfrm(3)](/wcsxfrm/3.md)

## STANDARDS

The **strxfrm**() function conforms to ISO/IEC 9899:1990 (“ISO C90”). The **strxfrm\_l**() function conforms to IEEE Std 1003.1-2008 (“POSIX.1”).