int main(int argc, char **argv) {
    FILE            *outstream;
    char            str[100];

    outstream=fopen("mypipe", "w");

    while (some condition) {
        str = createStr(); // creates my string
        str[strlen(str)-1] = 'n';
        fwrite(outstream, str, strlen(str)+1);
    }

    return 0;
}

while (my condition) {
    str = createStr(); // creates my string
    str[strlen(str)] = 'n';

    outstream=fopen("/var/run/gpspipe", "w");
    fputs(str, outstream);
    fclose(outstream);
}