#define _POSIX_C_SOURCE 200809L
#include <assert.h>
#include <stdio.h>
int main(int argc, char *argv[]) {
	FILE *pp = popen("cat", "w");
	assert(pp != NULL);
	{
		int n = fprintf(pp, "foo\n");
		assert(n >= 0);
	}
	{
		int err = pclose(pp);
		assert(err != -1);
	}
	return 0;
}