1 files changed, 57 insertions, 0 deletions
diff --git a/stdio/popen.c b/stdio/popen.c
new file mode 100644
index 0000000..50abc39
--- /dev/null
+++ b/stdio/popen.c
@@ -0,0 +1,57 @@
+/*-*- 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/errno.h"
+#include "libc/paths.h"
+#include "libc/runtime/runtime.h"
+#include "libc/stdio/internal.h"
+#include "libc/stdio/stdio.h"
+#include "libc/sysv/consts/f.h"
+#include "libc/sysv/consts/fd.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/sysv/errfuns.h"
+
+/**
+ * Spawns subprocess and returns pipe stream.
+ * @see pclose()
+ */
+FILE *popen(const char *cmdline, const char *mode) {
+  FILE *f;
+  int dir, flags, pipefds[2];
+  flags = fopenflags(mode);
+  if ((flags & O_ACCMODE) == O_RDONLY) {
+    dir = 0;
+  } else if ((flags & O_ACCMODE) == O_WRONLY) {
+    dir = 1;
+  } else {
+    errno = EINVAL;
+    return NULL;
+  }
+  if (pipe(pipefds) == -1) return NULL;
+  fcntl(pipefds[dir], F_SETFD, FD_CLOEXEC);
+  if (!(f = fdopen(pipefds[dir], mode))) abort();
+  if ((f->pid = vfork()) == -1) abort();
+  if (!f->pid) {
+    dup2(pipefds[!dir], !dir);
+    systemexec(cmdline);
+    _exit(127);
+  }
+  close(pipefds[!dir]);
+  return f;
+}