diff --git a/libc/calls/sigprocmask.c b/libc/calls/sigprocmask.c
index 9941de4c4..c59a64ce9 100644
--- a/libc/calls/sigprocmask.c
+++ b/libc/calls/sigprocmask.c
@@ -43,6 +43,8 @@
  * @param set is the new mask content (optional)
  * @param oldset will receive the old mask (optional) and can't overlap
  * @return 0 on success, or -1 w/ errno
+ * @raise EFAULT if `set` or `oldset` is bad memory
+ * @raise EINVAL if `how` is invalid
  * @asyncsignalsafe
  * @restartable
  * @vforksafe
diff --git a/libc/isystem/spawn.h b/libc/isystem/spawn.h
index 679428a19..638126051 100644
--- a/libc/isystem/spawn.h
+++ b/libc/isystem/spawn.h
@@ -1,5 +1,5 @@
 #ifndef COSMOPOLITAN_LIBC_ISYSTEM_SPAWN_H_
 #define COSMOPOLITAN_LIBC_ISYSTEM_SPAWN_H_
 #include "libc/calls/weirdtypes.h"
-#include "libc/stdio/spawn.h"
+#include "libc/stdio/posix_spawn.h"
 #endif /* COSMOPOLITAN_LIBC_ISYSTEM_SPAWN_H_ */
diff --git a/libc/log/oncrash.c b/libc/log/oncrash.c
index da017092b..d6ae1a992 100644
--- a/libc/log/oncrash.c
+++ b/libc/log/oncrash.c
@@ -278,7 +278,6 @@ static wontreturn relegated noinstrument void __minicrash(int sig,
  * @vforksafe
  */
 relegated void __oncrash(int sig, struct siginfo *si, ucontext_t *ctx) {
-  kprintf("oncrash\n");
   intptr_t rip;
   int me, owner;
   int gdbpid, err;
diff --git a/libc/stdio/popen.c b/libc/stdio/popen.c
index 2a3e62a64..dcf912835 100644
--- a/libc/stdio/popen.c
+++ b/libc/stdio/popen.c
@@ -54,7 +54,7 @@ FILE *popen(const char *cmdline, const char *mode) {
     switch ((pid = fork())) {
       case 0:
         _unassert(dup2(pipefds[!dir], !dir) == !dir);
-        // we can't rely on cloexec because cocmd builtins don't execev
+        // we can't rely on cloexec because cocmd builtins don't execve
         if (pipefds[0] != !dir) _unassert(!close(pipefds[0]));
         if (pipefds[1] != !dir) _unassert(!close(pipefds[1]));
         _Exit(cocmd(3, (char *[]){"popen", "-c", cmdline, 0}));
diff --git a/libc/stdio/spawn.c b/libc/stdio/posix_spawn.c
similarity index 55%
rename from libc/stdio/spawn.c
rename to libc/stdio/posix_spawn.c
index 904a750a5..705e7558b 100644
--- a/libc/stdio/spawn.c
+++ b/libc/stdio/posix_spawn.c
@@ -16,94 +16,95 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/assert.h"
 #include "libc/calls/calls.h"
-#include "libc/calls/struct/sched_param.h"
 #include "libc/calls/struct/sigaction.h"
+#include "libc/calls/struct/sigset.h"
 #include "libc/errno.h"
-#include "libc/fmt/fmt.h"
-#include "libc/intrin/kprintf.h"
 #include "libc/runtime/runtime.h"
-#include "libc/stdio/spawn.h"
-#include "libc/stdio/spawna.internal.h"
-#include "libc/str/str.h"
+#include "libc/stdio/posix_spawn.h"
+#include "libc/stdio/posix_spawn.internal.h"
+
+static int RunFileActions(struct _posix_faction *a) {
+  int t;
+  if (!a) return 0;
+  if (RunFileActions(a->next) == -1) return -1;
+  switch (a->action) {
+    case _POSIX_SPAWN_CLOSE:
+      return close(a->fildes);
+    case _POSIX_SPAWN_DUP2:
+      return dup2(a->fildes, a->newfildes);
+    case _POSIX_SPAWN_OPEN:
+      if ((t = open(a->path, a->oflag, a->mode)) == -1) return -1;
+      if (t != a->fildes) {
+        if (dup2(t, a->fildes) == -1) {
+          close(t);
+          return -1;
+        }
+        if (close(t) == -1) {
+          return -1;
+        }
+      }
+      return 0;
+    default:
+      unreachable;
+  }
+}
 
 /**
  * Spawns process the POSIX way.
  *
- * @param pid is non-NULL and will be set to child pid in parent
- * @param path of executable that is not PATH searched
+ * @param pid if non-null shall be set to child pid on success
+ * @param path is resolved path of program which is not `$PATH` searched
+ * @param file_actions specifies close(), dup2(), and open() operations
+ * @param attrp specifies signal masks, user ids, scheduling, etc.
+ * @param envp is environment variables, or `environ` if null
  * @return 0 on success or error number on failure
+ * @see posix_spawnp() for `$PATH` searching
  */
 int posix_spawn(int *pid, const char *path,
                 const posix_spawn_file_actions_t *file_actions,
                 const posix_spawnattr_t *attrp, char *const argv[],
                 char *const envp[]) {
-  unsigned mode;
+  int s, child;
   sigset_t allsigs;
   struct sigaction dfl;
-  char *p, *q, opath[PATH_MAX];
-  int s, fd, newfd, oflag, tempfd;
-  if (!(*pid = vfork())) {
-    if (attrp) {
-      if (attrp->posix_attr_flags & POSIX_SPAWN_SETPGROUP) {
-        if (setpgid(0, attrp->posix_attr_pgroup)) _Exit(127);
+  if (!(child = vfork())) {
+    if (attrp && *attrp) {
+      if ((*attrp)->flags & POSIX_SPAWN_SETPGROUP) {
+        if (setpgid(0, (*attrp)->pgroup)) _Exit(127);
       }
-      if (attrp->posix_attr_flags & POSIX_SPAWN_SETSIGMASK) {
-        sigprocmask(SIG_SETMASK, &attrp->posix_attr_sigmask, 0);
+      if ((*attrp)->flags & POSIX_SPAWN_SETSIGMASK) {
+        sigprocmask(SIG_SETMASK, &(*attrp)->sigmask, 0);
       }
-      if (attrp->posix_attr_flags & POSIX_SPAWN_RESETIDS) {
+      if ((*attrp)->flags & POSIX_SPAWN_RESETIDS) {
         setuid(getuid());
         setgid(getgid());
       }
-      if (attrp->posix_attr_flags & POSIX_SPAWN_SETSIGDEF) {
+      if ((*attrp)->flags & POSIX_SPAWN_SETSIGDEF) {
         dfl.sa_handler = SIG_DFL;
         dfl.sa_flags = 0;
         sigfillset(&allsigs);
         for (s = 0; sigismember(&allsigs, s); s++) {
-          if (sigismember(&attrp->posix_attr_sigdefault, s)) {
+          if (sigismember(&(*attrp)->sigdefault, s)) {
             if (sigaction(s, &dfl, 0) == -1) _Exit(127);
           }
         }
       }
     }
     if (file_actions) {
-      for (p = *file_actions; *p; p = strchr(p, ')') + 1) {
-        if (!strncmp(p, "close(", 6)) {
-          if (sscanf(p + 6, "%d)", &fd) != 1) _Exit(127);
-          if (close(fd) == -1) _Exit(127);
-        } else if (!strncmp(p, "dup2(", 5)) {
-          if (sscanf(p + 5, "%d,%d)", &fd, &newfd) != 2) _Exit(127);
-          if (dup2(fd, newfd) == -1) _Exit(127);
-        } else if (!strncmp(p, "open(", 5)) {
-          if (sscanf(p + 5, "%d,", &fd) != 1) _Exit(127);
-          p = strchr(p, ',') + 1;
-          q = strchr(p, '*');
-          if (!q || q - p >= PATH_MAX) _Exit(127);
-          strncpy(opath, p, q - p);
-          opath[q - p] = '\0';
-          if (sscanf(q + 1, "%o,%o)", &oflag, &mode) != 2) _Exit(127);
-          if (close(fd) == -1 && errno != EBADF) _Exit(127);
-          tempfd = open(opath, oflag, mode);
-          if (tempfd == -1) _Exit(127);
-          if (tempfd != fd) {
-            if (dup2(tempfd, fd) == -1) _Exit(127);
-            if (close(tempfd) == -1) _Exit(127);
-          }
-        } else {
-          _Exit(127);
-        }
+      if (RunFileActions(*file_actions) == -1) {
+        _Exit(127);
       }
     }
-    if (attrp) {
-      if (attrp->posix_attr_flags & POSIX_SPAWN_SETSCHEDULER) {
-        if (sched_setscheduler(0, attrp->posix_attr_schedpolicy,
-                               &attrp->posix_attr_schedparam) == -1) {
+    if (attrp && *attrp) {
+      if ((*attrp)->flags & POSIX_SPAWN_SETSCHEDULER) {
+        if (sched_setscheduler(0, (*attrp)->schedpolicy,
+                               &(*attrp)->schedparam) == -1) {
           if (errno != ENOSYS) _Exit(127);
         }
       }
-      if (attrp->posix_attr_flags & POSIX_SPAWN_SETSCHEDPARAM) {
-        if (sched_setparam(0, &attrp->posix_attr_schedparam) == -1) {
+      if ((*attrp)->flags & POSIX_SPAWN_SETSCHEDPARAM) {
+        if (sched_setparam(0, &(*attrp)->schedparam) == -1) {
           if (errno != ENOSYS) _Exit(127);
         }
       }
@@ -111,8 +112,10 @@ int posix_spawn(int *pid, const char *path,
     if (!envp) envp = environ;
     execve(path, argv, envp);
     _Exit(127);
-  } else {
-    if (*pid == -1) return errno;
+  } else if (child != -1) {
+    if (pid) *pid = child;
     return 0;
+  } else {
+    return errno;
   }
 }
diff --git a/libc/stdio/spawn.h b/libc/stdio/posix_spawn.h
similarity index 95%
rename from libc/stdio/spawn.h
rename to libc/stdio/posix_spawn.h
index 58c99474a..8f177d854 100644
--- a/libc/stdio/spawn.h
+++ b/libc/stdio/posix_spawn.h
@@ -13,8 +13,8 @@
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 COSMOPOLITAN_C_START_
 
-typedef char *posix_spawn_file_actions_t;
-typedef struct _posix_spawnattr posix_spawnattr_t;
+typedef struct _posix_spawna *posix_spawnattr_t;
+typedef struct _posix_faction *posix_spawn_file_actions_t;
 
 int posix_spawn(int *, const char *, const posix_spawn_file_actions_t *,
                 const posix_spawnattr_t *, char *const[], char *const[]);
diff --git a/libc/stdio/posix_spawn.internal.h b/libc/stdio/posix_spawn.internal.h
new file mode 100644
index 000000000..dc274275a
--- /dev/null
+++ b/libc/stdio/posix_spawn.internal.h
@@ -0,0 +1,41 @@
+#ifndef COSMOPOLITAN_LIBC_STDIO_SPAWNA_INTERNAL_H_
+#define COSMOPOLITAN_LIBC_STDIO_SPAWNA_INTERNAL_H_
+#include "libc/calls/struct/sched_param.h"
+#include "libc/calls/struct/sigset.h"
+
+#define _POSIX_SPAWN_CLOSE 1
+#define _POSIX_SPAWN_DUP2  2
+#define _POSIX_SPAWN_OPEN  3
+
+#if !(__ASSEMBLER__ + __LINKER__ + 0)
+COSMOPOLITAN_C_START_
+
+struct _posix_spawna {
+  char flags;
+  bool schedparam_isset;
+  bool schedpolicy_isset;
+  bool sigmask_isset;
+  int pgroup;
+  int schedpolicy;
+  struct sched_param schedparam;
+  sigset_t sigmask;
+  sigset_t sigdefault;
+};
+
+struct _posix_faction {
+  struct _posix_faction *next;
+  int action;
+  union {
+    int fildes;
+    int oflag;
+  };
+  union {
+    int newfildes;
+    unsigned mode;
+  };
+  const char *path;
+};
+
+COSMOPOLITAN_C_END_
+#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
+#endif /* COSMOPOLITAN_LIBC_STDIO_SPAWNA_INTERNAL_H_ */
diff --git a/libc/stdio/spawnf.c b/libc/stdio/posix_spawn_file_actions.c
similarity index 53%
rename from libc/stdio/spawnf.c
rename to libc/stdio/posix_spawn_file_actions.c
index acced624d..914a0a12c 100644
--- a/libc/stdio/spawnf.c
+++ b/libc/stdio/posix_spawn_file_actions.c
@@ -19,67 +19,98 @@
 #include "libc/errno.h"
 #include "libc/fmt/fmt.h"
 #include "libc/mem/mem.h"
-#include "libc/stdio/spawn.h"
+#include "libc/stdio/posix_spawn.h"
+#include "libc/stdio/posix_spawn.internal.h"
 #include "libc/str/str.h"
 
+static int AddFileAction(posix_spawn_file_actions_t *l,
+                         struct _posix_faction a) {
+  struct _posix_faction *ap;
+  if (!(ap = malloc(sizeof(*ap)))) return ENOMEM;
+  a.next = *l;
+  *ap = a;
+  *l = ap;
+  return 0;
+}
+
 /**
- * Creates object with no actions.
+ * Initializes posix_spawn() file actions list.
+ *
+ * @param file_actions will need posix_spawn_file_actions_destroy()
+ * @return 0 on success, or errno on error
  */
 int posix_spawn_file_actions_init(posix_spawn_file_actions_t *file_actions) {
-  *file_actions = malloc(sizeof(char));
-  if (!*file_actions) return ENOMEM;
-  strcpy(*file_actions, "");
+  *file_actions = 0;
   return 0;
 }
 
 /**
- * Frees object storage and make invalid.
+ * Destroys posix_spawn() file actions list.
+ *
+ * This function is safe to call multiple times.
+ *
+ * @param file_actions was initialized by posix_spawn_file_actions_init()
+ * @return 0 on success, or errno on error
  */
 int posix_spawn_file_actions_destroy(posix_spawn_file_actions_t *file_actions) {
-  free(*file_actions);
-  *file_actions = NULL;
-  return 0;
-}
-
-/**
- * Adds new action string to object.
- */
-static int add_to_file_actions(posix_spawn_file_actions_t *file_actions,
-                               char *new_action) {
-  *file_actions =
-      realloc(*file_actions, strlen(*file_actions) + strlen(new_action) + 1);
-  if (!*file_actions) return ENOMEM;
-  strcat(*file_actions, new_action);
+  if (*file_actions) {
+    posix_spawn_file_actions_destroy(&(*file_actions)->next);
+    free((*file_actions)->path);
+    free(*file_actions);
+    *file_actions = 0;
+  }
   return 0;
 }
 
 /**
  * Add a close action to object.
+ *
+ * @param file_actions was initialized by posix_spawn_file_actions_init()
+ * @return 0 on success, or errno on error
+ * @raise ENOMEM if we require more vespene gas
  */
 int posix_spawn_file_actions_addclose(posix_spawn_file_actions_t *file_actions,
                                       int fildes) {
-  char temp[100];
-  (sprintf)(temp, "close(%d)", fildes);
-  return add_to_file_actions(file_actions, temp);
+  return AddFileAction(file_actions, (struct _posix_faction){
+                                         .action = _POSIX_SPAWN_CLOSE,
+                                         .fildes = fildes,
+                                     });
 }
 
 /**
  * Add a dup2 action to object.
+ *
+ * @param file_actions was initialized by posix_spawn_file_actions_init()
+ * @return 0 on success, or errno on error
+ * @raise ENOMEM if we require more vespene gas
  */
 int posix_spawn_file_actions_adddup2(posix_spawn_file_actions_t *file_actions,
                                      int fildes, int newfildes) {
-  char temp[100];
-  (sprintf)(temp, "dup2(%d,%d)", fildes, newfildes);
-  return add_to_file_actions(file_actions, temp);
+  return AddFileAction(file_actions, (struct _posix_faction){
+                                         .action = _POSIX_SPAWN_DUP2,
+                                         .fildes = fildes,
+                                         .newfildes = newfildes,
+                                     });
 }
 
 /**
  * Add an open action to object.
+ *
+ * @param file_actions was initialized by posix_spawn_file_actions_init()
+ * @param filedes is what open() result gets duplicated to
+ * @param path will be safely copied
+ * @return 0 on success, or errno on error
+ * @raise ENOMEM if we require more vespene gas
  */
 int posix_spawn_file_actions_addopen(posix_spawn_file_actions_t *file_actions,
                                      int fildes, const char *path, int oflag,
                                      unsigned mode) {
-  char temp[100];
-  (sprintf)(temp, "open(%d,%s*%o,%o)", fildes, path, oflag, mode);
-  return add_to_file_actions(file_actions, temp);
+  if (!(path = strdup(path))) return ENOMEM;
+  return AddFileAction(file_actions, (struct _posix_faction){
+                                         .action = _POSIX_SPAWN_OPEN,
+                                         .fildes = fildes,
+                                         .path = path,
+                                         .oflag = oflag,
+                                         .mode = mode,
+                                     });
 }
diff --git a/libc/stdio/posix_spawnattr.c b/libc/stdio/posix_spawnattr.c
new file mode 100644
index 000000000..44a8c29ad
--- /dev/null
+++ b/libc/stdio/posix_spawnattr.c
@@ -0,0 +1,213 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/calls/struct/sigset.h"
+#include "libc/errno.h"
+#include "libc/mem/mem.h"
+#include "libc/stdio/posix_spawn.h"
+#include "libc/stdio/posix_spawn.internal.h"
+#include "libc/sysv/consts/sig.h"
+
+/**
+ * Initialize posix_spawn() attributes object with default values.
+ *
+ * @param attr needs to be passed to posix_spawnattr_destroy() later
+ * @return 0 on success, or errno on error
+ * @raise ENOMEM if we require more vespene gas
+ */
+int posix_spawnattr_init(posix_spawnattr_t *attr) {
+  int e, rc;
+  struct _posix_spawna *a;
+  e = errno;
+  errno = 0;
+  if ((a = calloc(1, sizeof(*a)))) {
+    a->flags = 0;
+    a->pgroup = 0;
+    sigemptyset(&a->sigdefault);
+    a->schedpolicy = sched_getscheduler(0);
+    sched_getparam(0, &a->schedparam);
+  }
+  rc = errno;
+  errno = e;
+  return rc;
+}
+
+/**
+ * Destroys posix_spawn() attributes object.
+ *
+ * This function is safe to call multiple times.
+ *
+ * @param attr was initialized by posix_spawnattr_init()
+ * @return 0 on success, or errno on error
+ */
+int posix_spawnattr_destroy(posix_spawnattr_t *attr) {
+  if (*attr) {
+    free(*attr);
+    *attr = 0;
+  }
+  return 0;
+}
+
+/**
+ * Gets posix_spawn() flags.
+ *
+ * @param attr was initialized by posix_spawnattr_init()
+ * @return 0 on success, or errno on error
+ */
+int posix_spawnattr_getflags(const posix_spawnattr_t *attr, short *flags) {
+  *flags = (*attr)->flags;
+  return 0;
+}
+
+/**
+ * Sets posix_spawn() flags.
+ *
+ * Setting these flags is needed in order for the other setters in this
+ * function to take effect.
+ *
+ * @param attr was initialized by posix_spawnattr_init()
+ * @param flags may have any of the following
+ *     - `POSIX_SPAWN_RESETIDS`
+ *     - `POSIX_SPAWN_SETPGROUP`
+ *     - `POSIX_SPAWN_SETSIGDEF`
+ *     - `POSIX_SPAWN_SETSIGMASK`
+ *     - `POSIX_SPAWN_SETSCHEDPARAM`
+ *     - `POSIX_SPAWN_SETSCHEDULER`
+ * @return 0 on success, or errno on error
+ * @raise EINVAL if `flags` has invalid bits
+ */
+int posix_spawnattr_setflags(posix_spawnattr_t *attr, short flags) {
+  if (flags & ~(POSIX_SPAWN_RESETIDS | POSIX_SPAWN_SETPGROUP |
+                POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK |
+                POSIX_SPAWN_SETSCHEDPARAM | POSIX_SPAWN_SETSCHEDULER)) {
+    return EINVAL;
+  }
+  (*attr)->flags = flags;
+  return 0;
+}
+
+int posix_spawnattr_getpgroup(const posix_spawnattr_t *attr, int *pgroup) {
+  *pgroup = (*attr)->pgroup;
+  return 0;
+}
+
+int posix_spawnattr_setpgroup(posix_spawnattr_t *attr, int pgroup) {
+  (*attr)->pgroup = pgroup;
+  return 0;
+}
+
+/**
+ * Gets scheduler policy that'll be used for spawned process.
+ *
+ * If the setter wasn't called then this function will return the
+ * scheduling policy of the current process.
+ *
+ * @param attr was initialized by posix_spawnattr_init()
+ * @param schedpolicy receives the result
+ * @return 0 on success, or errno on error
+ */
+int posix_spawnattr_getschedpolicy(const posix_spawnattr_t *attr,
+                                   int *schedpolicy) {
+  if (!(*attr)->schedpolicy_isset) {
+    (*attr)->schedpolicy = sched_getscheduler(0);
+    (*attr)->schedpolicy_isset = true;
+  }
+  *schedpolicy = (*attr)->schedpolicy;
+  return 0;
+}
+
+/**
+ * Specifies scheduler policy override for spawned process.
+ *
+ * Scheduling policies are inherited by default. Use this to change it.
+ *
+ * @param attr was initialized by posix_spawnattr_init()
+ * @param schedpolicy receives the result
+ * @return 0 on success, or errno on error
+ */
+int posix_spawnattr_setschedpolicy(posix_spawnattr_t *attr, int schedpolicy) {
+  (*attr)->schedpolicy = schedpolicy;
+  (*attr)->schedpolicy_isset = true;
+  return 0;
+}
+
+/**
+ * Gets scheduler parameter that'll be used for spawned process.
+ *
+ * If the setter wasn't called then this function will return the
+ * scheduling parameter of the current process.
+ *
+ * @param attr was initialized by posix_spawnattr_init()
+ * @param schedparam receives the result
+ * @return 0 on success, or errno on error
+ */
+int posix_spawnattr_getschedparam(const posix_spawnattr_t *attr,
+                                  struct sched_param *schedparam) {
+  if (!(*attr)->schedparam_isset) {
+    sched_getparam(0, &(*attr)->schedparam);
+    (*attr)->schedparam_isset = true;
+  }
+  *schedparam = (*attr)->schedparam;
+  return 0;
+}
+
+/**
+ * Specifies scheduler parameter override for spawned process.
+ *
+ * Scheduling parameters are inherited by default. Use this to change it.
+ *
+ * @param attr was initialized by posix_spawnattr_init()
+ * @param schedparam receives the result
+ * @return 0 on success, or errno on error
+ */
+int posix_spawnattr_setschedparam(posix_spawnattr_t *attr,
+                                  const struct sched_param *schedparam) {
+  (*attr)->schedparam = *schedparam;
+  (*attr)->schedparam_isset = true;
+  return 0;
+}
+
+int posix_spawnattr_getsigmask(const posix_spawnattr_t *attr,
+                               sigset_t *sigmask) {
+  if (!(*attr)->sigmask_isset) {
+    sigprocmask(SIG_SETMASK, 0, &(*attr)->sigmask);
+    (*attr)->sigmask_isset = true;
+  }
+  *sigmask = (*attr)->sigmask;
+  return 0;
+}
+
+int posix_spawnattr_setsigmask(posix_spawnattr_t *attr,
+                               const sigset_t *sigmask) {
+  (*attr)->sigmask = *sigmask;
+  (*attr)->sigmask_isset = true;
+  return 0;
+}
+
+int posix_spawnattr_getsigdefault(const posix_spawnattr_t *attr,
+                                  sigset_t *sigdefault) {
+  *sigdefault = (*attr)->sigdefault;
+  return 0;
+}
+
+int posix_spawnattr_setsigdefault(posix_spawnattr_t *attr,
+                                  const sigset_t *sigdefault) {
+  (*attr)->sigdefault = *sigdefault;
+  return 0;
+}
diff --git a/libc/stdio/spawnp.c b/libc/stdio/posix_spawnp.c
similarity index 98%
rename from libc/stdio/spawnp.c
rename to libc/stdio/posix_spawnp.c
index 67b9d0d67..3ca42ab6a 100644
--- a/libc/stdio/spawnp.c
+++ b/libc/stdio/posix_spawnp.c
@@ -18,7 +18,7 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/errno.h"
-#include "libc/stdio/spawn.h"
+#include "libc/stdio/posix_spawn.h"
 
 /**
  * Spawns process the POSIX way w/ PATH search.
diff --git a/libc/stdio/spawna.c b/libc/stdio/spawna.c
deleted file mode 100644
index 9a923f94c..000000000
--- a/libc/stdio/spawna.c
+++ /dev/null
@@ -1,105 +0,0 @@
-/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
-│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
-╞══════════════════════════════════════════════════════════════════════════════╡
-│ Copyright 2021 Justine Alexandra Roberts Tunney                              │
-│                                                                              │
-│ Permission to use, copy, modify, and/or distribute this software for         │
-│ any purpose with or without fee is hereby granted, provided that the         │
-│ above copyright notice and this permission notice appear in all copies.      │
-│                                                                              │
-│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
-│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
-│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
-│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
-│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
-│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
-│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
-│ PERFORMANCE OF THIS SOFTWARE.                                                │
-╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/calls/calls.h"
-#include "libc/stdio/spawn.h"
-#include "libc/stdio/spawna.internal.h"
-
-/**
- * Initialize object with default values.
- */
-int posix_spawnattr_init(posix_spawnattr_t *attr) {
-  attr->posix_attr_flags = 0;
-  attr->posix_attr_pgroup = 0;
-  sigprocmask(0, NULL, &attr->posix_attr_sigmask);
-  sigemptyset(&attr->posix_attr_sigdefault);
-  attr->posix_attr_schedpolicy = sched_getscheduler(0);
-  sched_getparam(0, &attr->posix_attr_schedparam);
-  return 0;
-}
-
-int posix_spawnattr_destroy(posix_spawnattr_t *attr) {
-  return 0;
-}
-
-int posix_spawnattr_getflags(const posix_spawnattr_t *attr, short *flags) {
-  *flags = attr->posix_attr_flags;
-  return 0;
-}
-
-int posix_spawnattr_setflags(posix_spawnattr_t *attr, short flags) {
-  attr->posix_attr_flags = flags;
-  return 0;
-}
-
-int posix_spawnattr_getpgroup(const posix_spawnattr_t *attr, int *pgroup) {
-  *pgroup = attr->posix_attr_pgroup;
-  return 0;
-}
-
-int posix_spawnattr_setpgroup(posix_spawnattr_t *attr, int pgroup) {
-  attr->posix_attr_pgroup = pgroup;
-  return 0;
-}
-
-int posix_spawnattr_getschedpolicy(const posix_spawnattr_t *attr,
-                                   int *schedpolicy) {
-  *schedpolicy = attr->posix_attr_schedpolicy;
-  return 0;
-}
-
-int posix_spawnattr_setschedpolicy(posix_spawnattr_t *attr, int schedpolicy) {
-  attr->posix_attr_schedpolicy = schedpolicy;
-  return 0;
-}
-
-int posix_spawnattr_getschedparam(const posix_spawnattr_t *attr,
-                                  struct sched_param *schedparam) {
-  *schedparam = attr->posix_attr_schedparam;
-  return 0;
-}
-
-int posix_spawnattr_setschedparam(posix_spawnattr_t *attr,
-                                  const struct sched_param *schedparam) {
-  attr->posix_attr_schedparam = *schedparam;
-  return 0;
-}
-
-int posix_spawnattr_getsigmask(const posix_spawnattr_t *attr,
-                               sigset_t *sigmask) {
-  *sigmask = attr->posix_attr_sigmask;
-  return 0;
-}
-
-int posix_spawnattr_setsigmask(posix_spawnattr_t *attr,
-                               const sigset_t *sigmask) {
-  attr->posix_attr_sigmask = *sigmask;
-  return 0;
-}
-
-int posix_spawnattr_getsigdefault(const posix_spawnattr_t *attr,
-                                  sigset_t *sigdefault) {
-  *sigdefault = attr->posix_attr_sigdefault;
-  return 0;
-}
-
-int posix_spawnattr_setsigdefault(posix_spawnattr_t *attr,
-                                  const sigset_t *sigdefault) {
-  attr->posix_attr_sigdefault = *sigdefault;
-  return 0;
-}
diff --git a/libc/stdio/spawna.internal.h b/libc/stdio/spawna.internal.h
deleted file mode 100644
index 2635aca1f..000000000
--- a/libc/stdio/spawna.internal.h
+++ /dev/null
@@ -1,19 +0,0 @@
-#ifndef COSMOPOLITAN_LIBC_STDIO_SPAWNA_INTERNAL_H_
-#define COSMOPOLITAN_LIBC_STDIO_SPAWNA_INTERNAL_H_
-#include "libc/calls/struct/sched_param.h"
-#include "libc/calls/struct/sigset.h"
-#if !(__ASSEMBLER__ + __LINKER__ + 0)
-COSMOPOLITAN_C_START_
-
-struct _posix_spawnattr {
-  int16_t posix_attr_flags;
-  int32_t posix_attr_pgroup;
-  sigset_t posix_attr_sigmask;
-  sigset_t posix_attr_sigdefault;
-  int32_t posix_attr_schedpolicy;
-  struct sched_param posix_attr_schedparam;
-};
-
-COSMOPOLITAN_C_END_
-#endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
-#endif /* COSMOPOLITAN_LIBC_STDIO_SPAWNA_INTERNAL_H_ */
diff --git a/libc/stdio/stdio.mk b/libc/stdio/stdio.mk
index 94b395fde..3157a33e9 100644
--- a/libc/stdio/stdio.mk
+++ b/libc/stdio/stdio.mk
@@ -57,6 +57,8 @@ o//libc/stdio/appendw.o: private			\
 		OVERRIDE_CFLAGS +=			\
 			-Os
 
+o/$(MODE)/libc/stdio/posix_spawnattr.o			\
+o/$(MODE)/libc/stdio/posix_spawn_file_actions.o		\
 o/$(MODE)/libc/stdio/mt19937.o: private			\
 		OVERRIDE_CFLAGS +=			\
 			-ffunction-sections
diff --git a/test/libc/calls/sched_getaffinity_test.c b/test/libc/calls/sched_getaffinity_test.c
index 055d91fe4..950bdbdc7 100644
--- a/test/libc/calls/sched_getaffinity_test.c
+++ b/test/libc/calls/sched_getaffinity_test.c
@@ -23,7 +23,7 @@
 #include "libc/intrin/popcnt.h"
 #include "libc/intrin/safemacros.internal.h"
 #include "libc/runtime/runtime.h"
-#include "libc/stdio/spawn.h"
+#include "libc/stdio/posix_spawn.h"
 #include "libc/testlib/subprocess.h"
 #include "libc/testlib/testlib.h"
 #include "libc/thread/thread.h"
diff --git a/test/libc/stdio/spawn_test.c b/test/libc/stdio/spawn_test.c
index 95fabe42a..9ec4da203 100644
--- a/test/libc/stdio/spawn_test.c
+++ b/test/libc/stdio/spawn_test.c
@@ -19,10 +19,11 @@
 #include "libc/calls/calls.h"
 #include "libc/dce.h"
 #include "libc/fmt/conv.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/intrin/safemacros.internal.h"
 #include "libc/runtime/internal.h"
 #include "libc/runtime/runtime.h"
-#include "libc/stdio/spawn.h"
+#include "libc/stdio/posix_spawn.h"
 #include "libc/stdio/stdio.h"
 #include "libc/sysv/consts/auxv.h"
 #include "libc/sysv/consts/o.h"