diff --git a/build-aux/configure-lib.sh b/build-aux/configure-lib.sh
index 0f9bc8f9..f1df1542 100644
--- a/build-aux/configure-lib.sh
+++ b/build-aux/configure-lib.sh
@@ -339,7 +339,9 @@ lib/stdio/feof.c
 lib/stdio/fgets.c
 lib/stdio/freopen.c
 lib/stdio/fscanf.c
+lib/stdio/pclose.c
 lib/stdio/perror.c
+lib/stdio/popen.c
 lib/stdio/rewind.c
 lib/stdio/vfscanf.c
 lib/stdlib/__exit.c
@@ -385,8 +387,6 @@ lib/stub/gmtime.c
 lib/stub/log.c
 lib/stub/mktime.c
 lib/stub/modf.c
-lib/stub/pclose.c
-lib/stub/popen.c
 lib/stub/pow.c
 lib/stub/rand.c
 lib/stub/setbuf.c
diff --git a/lib/stub/pclose.c b/lib/stdio/pclose.c
similarity index 62%
rename from lib/stub/pclose.c
rename to lib/stdio/pclose.c
index 14f15bdd..20d91206 100644
--- a/lib/stub/pclose.c
+++ b/lib/stdio/pclose.c
@@ -1,6 +1,6 @@
 /* -*-comment-start: "//";comment-end:""-*-
  * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ * Copyright © 2022 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
  *
  * This file is part of GNU Mes.
  *
@@ -20,14 +20,31 @@
 
 #include <mes/lib.h>
 #include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
 
 int
-pclose (int x)
+pclose (FILE *stream)
 {
-  static int stub = 0;
-  if (__mes_debug () && !stub)
-    eputs ("pclose stub\n");
-  stub = 1;
-  errno = 0;
-  return 0;
+  int filedes = fileno (stream);
+  __ungetc_init ();
+  pid_t pid = __ungetc_buf[filedes];
+  if (!pid)
+    {
+      errno = EINVAL;
+      return -1;
+    }
+
+  if (fclose (stream))
+    return -1;
+
+  int status;
+  pid_t child_pid = waitpid (pid, &status, 0);
+  if (child_pid != pid)
+    return -1;
+
+  return status;
 }
diff --git a/lib/stdio/popen.c b/lib/stdio/popen.c
new file mode 100644
index 00000000..71b43204
--- /dev/null
+++ b/lib/stdio/popen.c
@@ -0,0 +1,114 @@
+/* -*-comment-start: "//";comment-end:""-*-
+ * GNU Mes --- Maxwell Equations of Software
+ * Copyright © 2022 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
+ *
+ * This file is part of GNU Mes.
+ *
+ * GNU Mes is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * GNU Mes is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <mes/lib.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#ifndef SHELL_FILE_NAME
+#define	SHELL_FILE_NAME "/bin/sh"
+#endif
+#ifndef SHELL_COMMAND_NAME
+#define	SHELL_COMMAND_NAME "sh"
+#endif
+
+extern int *__ungetc_buf;
+
+FILE *
+popen (char const *command, char const *mode)
+{
+  if (!command || !mode || (*mode != 'r' && *mode != 'w'))
+    {
+      errno = EINVAL;
+      return 0;
+    }
+
+  int pipedes[2];
+  if (pipe (pipedes) < 0)
+    return NULL;
+
+  pid_t pid = fork ();
+  if (pid == -1)
+    {
+      close (pipedes[0]);
+      close (pipedes[1]);
+      return 0;
+    }
+  else if (pid == 0)
+    {
+      // child
+      int dup = (*mode == 'w'
+                 ? dup2 (pipedes[STDIN], STDIN)
+                 : dup2 (pipedes[STDOUT], STDOUT))
+      if (dup < 0)
+	_exit (127);
+
+      close (pipedes[STDIN]);
+      close (pipedes[STDOUT]);
+
+      char const *argv[4];
+      argv[0] = SHELL_COMMAND_NAME;
+      argv[1] = "-c";
+      argv[2] = command;
+      argv[3] = 0;
+      execve (SHELL_FILE_NAME, (char *const *) argv, environ);
+      _exit (127);
+    }
+
+  FILE *stream;
+  // parent
+  if (*mode == 'r')
+    {
+      close (pipedes[STDOUT]);
+      fcntl (pipedes[STDIN], F_SETFD, FD_CLOEXEC);
+      stream = fdopen (pipedes[STDIN], mode);
+    }
+  else
+    {
+      close (pipedes[STDIN]);
+      fcntl (pipedes[STDOUT], F_SETFD, FD_CLOEXEC);
+      stream = fdopen (pipedes[STDOUT], mode);
+    }
+
+  if (!stream)
+    {
+      int save_errno = errno;
+      kill (pid, SIGKILL);
+      if (!stream)
+        close (pipedes[*mode == 'r' ? STDOUT : STDIN]);
+      else
+        fclose (stream);
+      waitpid (pid, (int *)0, 0);
+      errno = save_errno;
+      return 0;
+    }
+
+  int filedes = fileno (stream);
+  // XXX misuse ungetc buffer for PID
+  // XXX TODO: make proper FILE struct
+  __ungetc_init ();
+  __ungetc_set (filedes, pidchild);
+  return stream;
+}
diff --git a/lib/stub/popen.c b/lib/stub/popen.c
deleted file mode 100644
index 77fd5f95..00000000
--- a/lib/stub/popen.c
+++ /dev/null
@@ -1,33 +0,0 @@
-/* -*-comment-start: "//";comment-end:""-*-
- * GNU Mes --- Maxwell Equations of Software
- * Copyright © 2018 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
- *
- * This file is part of GNU Mes.
- *
- * GNU Mes is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 3 of the License, or (at
- * your option) any later version.
- *
- * GNU Mes is distributed in the hope that it will be useful, but
- * WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with GNU Mes.  If not, see <http://www.gnu.org/licenses/>.
- */
-
-#include <mes/lib.h>
-#include <errno.h>
-
-int
-popen (int x)
-{
-  static int stub = 0;
-  if (__mes_debug () && !stub)
-    eputs ("popen stub\n");
-  stub = 1;
-  errno = 0;
-  return 0;
-}