#define _XOPEN_SOURCE 700

#include <stdio.h>
#include <stdlib.h>
#include <time.h>

int main() {

    const char * templatePath = "datemsk.txt";
    FILE * templateFile = fopen( templatePath, "w" );

    if ( templateFile == NULL ) {
        perror( "fopen" );
        return EXIT_FAILURE;
    }

    fputs( "%Y-%m-%d\n", templateFile );
    fclose( templateFile );

    if ( setenv( "DATEMSK", templatePath, 1 ) == -1 ) {
        perror( "setenv" );
        remove( templatePath );
        return EXIT_FAILURE;
    }

    struct tm * date = getdate( "2024-01-15" );
    remove( templatePath );

    if ( date == NULL ) {
        fprintf( stderr, "getdate_err == %d\n", getdate_err );
        return EXIT_FAILURE;
    }

    printf( "%04d-%02d-%02d\n",
            date->tm_year + 1900, date->tm_mon + 1, date->tm_mday );

    return EXIT_SUCCESS;
}