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spawn.c

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+/*
+ * Copyright 2008-2013 Various Authors
+ * Copyright 2005 Timo Hirvonen
+ *
+ * This program 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 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program 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 this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "spawn.h"
+#include "file.h"
+
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+
+int spawn(char *argv[], int *status, int do_wait)
+{
+	pid_t pid;
+	int err_pipe[2];
+
+	if (pipe(err_pipe) == -1)
+		return -1;
+
+	pid = fork();
+	if (pid == -1) {
+		/* error */
+		return -1;
+	} else if (pid == 0) {
+		/* child */
+		int dev_null, err, i;
+
+		/* create grandchild and exit child to avoid zombie processes */
+		if (!do_wait) {
+			switch (fork()) {
+			case 0:
+				/* grandchild */
+				break;
+			case -1:
+				/* error */
+				_exit(127);
+			default:
+				/* parent of grandchild */
+				_exit(0);
+			}
+		}
+
+		close(err_pipe[0]);
+		fcntl(err_pipe[1], F_SETFD, FD_CLOEXEC);
+
+		/* redirect stdout and stderr to /dev/null if possible */
+		dev_null = open("/dev/null", O_WRONLY);
+		if (dev_null != -1) {
+			dup2(dev_null, 1);
+			dup2(dev_null, 2);
+		}
+
+		/* not interactive, close stdin */
+		close(0);
+
+		/* close unused fds */
+		for (i = 3; i < 30; i++)
+			close(i);
+
+		execvp(argv[0], argv);
+
+		/* error */
+		err = errno;
+		write_all(err_pipe[1], &err, sizeof(int));
+		exit(1);
+	} else {
+		/* parent */
+		int rc, errno_save, child_errno, tmp;
+
+		close(err_pipe[1]);
+		rc = read_all(err_pipe[0], &child_errno, sizeof(int));
+		errno_save = errno;
+		close(err_pipe[0]);
+
+		if (!do_wait)
+			status = &tmp;
+		waitpid(pid, status, 0);
+
+		if (rc == -1) {
+			errno = errno_save;
+			return -1;
+		}
+		if (rc == sizeof(int)) {
+			errno = child_errno;
+			return -1;
+		}
+		if (rc != 0) {
+			errno = EMSGSIZE;
+			return -1;
+		}
+		return 0;
+	}
+}