C:setlocale

lastmod 2024-10-24created 2016-12-119 edits

Sets or gets the runtime locale.

Category

The portion of the locale affected. One of the following constant values defined as macros in clocale.

locale parameter

• "C": The minimal "C" locale.
• "": The default locale of the current environment.
• NULL: Does not change the locale environment; lets you check the current value.

Simple example

setlocale (LC_ALL, "");

Sets the locale by consulting the appropriate environment variables and returns its value. Environment variables are consulted in the order LC_ALL, the other categories, then the LANG variable. Once the variable value is found, it consults locale.alias (e.g. /usr/share/locale/), then finds an available locale by trimming from the end in units of @ . _, in order.

locale = setlocale (LC_ALL, NULL);

An example that uses the return value only to find out the current locale value for a category, without changing the locale value.

Example

#include <cstdio>
#include <clocale>
#include <ctime>
#include <cwchar>

int main()
{
    std::setlocale(LC_ALL, "en_US.UTF-8"); // the C locale will be the UTF-8 enabled English
    std::setlocale(LC_NUMERIC, "de_DE");   // decimal dot will be German
    std::setlocale(LC_TIME, "ja_JP");      // date/time formatting will be Japanese
    wchar_t str[100];
    std::time_t t = std::time(nullptr);
    std::wcsftime(str, 100, L"%A %c", std::localtime(&t));
    std::wprintf(L"Number: %.2f\nDate: %Ls\n", 3.14, str);
}

Troubleshooting

warning: setlocale: LC_ALL: cannot change locale

• ubuntu - Linode Lish bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8) - Stack Overflow
• Handling the locale error "warning: setlocale: LC_ALL: cannot change locale" on Linux

It is usually printed in bash something like this:

bash: warning: setlocale: LC_ALL: cannot change locale (en_US.UTF-8)

The warning means the system is trying to set the printed locale (in this case "en_US.UTF-8"), but that locale is not installed or not configured correctly.

Check the locales available on the current system:

locale -a

Ways to fix this are as follows.

Using locale-gen on Debian/Ubuntu-based systems:

sudo locale-gen en_US.UTF-8
sudo update-locale LANG=en_US.UTF-8

On CentOS/RHEL-based systems, use localedef:

sudo localedef -v -c -i en_US -f UTF-8 en_US.UTF-8

Reconfigure with dpkg-reconfigure:

sudo dpkg-reconfigure locales

Installing the package on Red Hat-based systems:

yum install glibc-langpack-en

Installing the package on Debian-based systems:

sudo apt install language-pack-en

If the locale has been generated but the error still occurs, you can set the locale environment variables directly. To do so, add the following lines to ~/.bashrc or /etc/environment:

export LANG=en_US.UTF-8
export LANGUAGE=en_US.UTF-8
export LC_ALL=en_US.UTF-8

See also

• clocale

Favorite site

• MSDN - setlocale, _wsetlocale ¹
• Dark Programmer :: How to use setlocale
• IBM Knowledge Center - setlocale() — Set locale
• Joinc - Linux locale settings
• [Recommended] What is a locale ²

References