libs/libc/unistd/: Add a crippled version of daemon().
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Gregory Nutt
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d291cb884c
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5a89459783
@ -290,6 +290,7 @@ void _exit(int status) noreturn_function;
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unsigned int sleep(unsigned int seconds);
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int usleep(useconds_t usec);
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int pause(void);
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int daemon(int nochdir, int noclose);
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/* File descriptor operations */
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@ -35,7 +35,7 @@
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# Add the unistd C files to the build
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CSRCS += lib_access.c lib_swab.c lib_sysconf.c
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CSRCS += lib_access.c lib_daemon.c lib_swab.c lib_sysconf.c
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CSRCS += lib_getopt.c lib_getoptargp.c lib_getoptindp.c lib_getoptoptp.c
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ifneq ($(CONFIG_NFILE_DESCRIPTORS),0)
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172
libs/libc/unistd/lib_daemon.c
Normal file
172
libs/libc/unistd/lib_daemon.c
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@ -0,0 +1,172 @@
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/****************************************************************************
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* libs/libc/unistd/lib_daemon.c
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*
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* Copyright (C) 2016 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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 way which behaves slightly differently).
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* The interfaces defined at OpenGroup.org are the interfaces that govern
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* NuttX. deamon() 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 is not 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.) On
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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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* vim fork.
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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 CONFIG_NFILE_DESCRIPTORS > 0
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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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/* Make sure the stdin, stdout, and stderr are closed */
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(void)fclose(stdin);
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(void)fclose(stdout);
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(void)fclose(stderr);
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/* Dup the fd to create standard fd 0-2 */
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(void)dup2(fd, 0);
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(void)dup2(fd, 1);
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(void)dup2(fd, 2);
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/* fdopen to get the stdin, stdout and stderr streams. The
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* following logic depends on the fact that the library layer
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* will allocate FILEs in order. And since we closed stdin,
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* stdout, and stderr above, that is what we should get.
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*
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* fd = 0 is stdin (read-only)
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* fd = 1 is stdout (write-only, append)
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* fd = 2 is stderr (write-only, append)
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*/
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(void)fdopen(0, "r");
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(void)fdopen(1, "a");
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(void)fdopen(2, "a");
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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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(void)close(fd);
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}
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}
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#endif
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return OK;
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}
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#endif /* CONFIG_BUILD_FLAT=y || !__KERNEL__ */
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