146 lines
4.7 KiB
C
146 lines
4.7 KiB
C
/****************************************************************************
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* libs/libc/unistd/lib_daemon.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <fcntl.h>
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/* Not appropriate for use within the OS */
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#if defined(CONFIG_BUILD_FLAT) || !defined(__KERNEL__)
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: daemon
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*
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* Description:
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* The daemon() function is for programs wishing to detach themselves from
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* the controlling terminal and run in the background as system daemons.
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*
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* NOTE: daemon() is a non-standard GNU C library interface (based on a
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* BSD interface of the same name which behaves slightly differently).
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* The interfaces defined at OpenGroup.org are the interfaces that govern
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* NuttX. daemon() is only described in the Linux man pages like:
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* http://man7.org/linux/man-pages/man3/daemon.3.html
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*
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* Limitations:
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* NuttX does not implement controlling terminals so the primary purpose
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* of this interface cannot be supported. Additional operations controlled
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* by input parameters are supported, however.
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*
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* It is not possible to support a true Linux daemon() helper function
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* because it is designed to work only in the Linux environment and cannot
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* be translated to NuttX. The above mentioned web page states:
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*
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* (This function forks, and if the fork(2) succeeds, the parent calls
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* _exit(2), so that further errors are seen by the child only.)
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*
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* So the basic operation of the NuttX daemon() is different. The GNU C
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* library daemon() begins will logic like:
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*
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* switch (fork())
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* {
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* case -1:
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* return -1;
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* case 0:
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* break;
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* default:
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* exit(0);
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* }
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*
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* This implementation begins essentially 'pretending' that we forked
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* and that the fork was successful and that we are the child of the
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* fork.
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*
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* REVISIT: Ideally we should remove the parent information from the
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* the new daemon's group data structure. That would have a similar
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* effect to the above fork() operation.
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*
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* Input Parameters:
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* nochdir - If nochdir is zero, daemon() changes the process's current
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* working directory to the root directory ("/"); otherwise, the current
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* working directory is left unchanged.
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* noclose - If noclose is zero, daemon() redirects standard input,
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* standard output and standard error to /dev/null; otherwise, no changes
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* are made to these file descriptors.
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*
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* Returned Value:
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* 0 is returned on success; otherwise, -1 is returned with errno set
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* appropriately.
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*
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****************************************************************************/
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int daemon(int nochdir, int noclose)
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{
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#ifndef CONFIG_DISABLE_ENVIRON
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if (nochdir == 0)
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{
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int ret = chdir("/");
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if (ret < 0)
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{
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return -1; /* chdir() will set the errno variable */
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}
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}
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#endif
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if (noclose == 0)
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{
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int fd = open("/dev/null", O_RDWR);
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if (fd < 0)
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{
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return -1;
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}
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#ifdef CONFIG_FILE_STREAM
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/* Make sure the stdout, and stderr are flushed */
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fflush(stdout);
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fflush(stderr);
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#endif
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/* Dup the fd to create standard fd 0-2 */
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dup2(fd, 0);
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dup2(fd, 1);
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dup2(fd, 2);
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/* We can close the original file descriptor now (unless it was
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* one of* 0-2)
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*/
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if (fd > 2)
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{
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close(fd);
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}
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}
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return OK;
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}
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#endif /* CONFIG_BUILD_FLAT=y || !__KERNEL__ */
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