Simplify daemon and always close file descriptors
Use daemon(3) to daemonise rather than writing our own code. Since we use the mode of daemon(3) which closes the standard 3 file descriptors, if the user requests logging to one of those we dup(2) the original first. We must also take care to always close any newly-opened file descriptors before execve(2) of the child.
This commit is contained in:
parent
c55693ce1c
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639944b905
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@ -1,8 +1,8 @@
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/* daemonitor/src/daemonitor/200_log.c
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*
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* (c)2007, Laurence Withers, <l@lwithers.me.uk>.
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* Released under the GNU GPLv3. See file COPYING or
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* http://www.gnu.org/copyleft/gpl.html for details.
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* Copyright: ©2007–2012, Laurence Withers.
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* Author: Laurence Withers <l@lwithers.me.uk>
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* License: GPLv3
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*/
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@ -170,16 +170,25 @@ void log_func_syslog(int level, const char* fmt, ...)
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/* log_destination_set()
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* Set `log_func' function pointer.
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*/
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void log_destination_set(enum log_destination_t dest)
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void
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log_destination_set(enum log_destination_t dest)
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{
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switch(dest) {
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case log_destination_stdout:
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log_func_fd = STDOUT_FILENO;
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log_func_fd = dup(STDOUT_FILENO);
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if(log_func_fd == -1) {
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printf("dup() failed: %m.");
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exit(1);
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}
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log_func = log_func_file;
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break;
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case log_destination_stderr:
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log_func_fd = STDERR_FILENO;
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log_func_fd = dup(STDERR_FILENO);
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if(log_func_fd == -1) {
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fprintf(stderr, "dup() failed: %m.");
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exit(1);
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}
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log_func = log_func_file;
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break;
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@ -210,6 +219,5 @@ int log_destination_set_file(const char* filename)
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/* options for text editors
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kate: replace-trailing-space-save true; space-indent true; tab-width 4;
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vim: expandtab:ts=4:sw=4
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*/
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@ -1,160 +0,0 @@
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/* daemonitor/src/daemonitor/400_daemon.c
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*
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* (c)2007, Laurence Withers, <l@lwithers.me.uk>.
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* Released under the GNU GPLv3. See file COPYING or
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* http://www.gnu.org/copyleft/gpl.html for details.
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*/
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/* DAEMON ROUTINES ********************************************************************************
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*
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* This file provides the daemonise() routine, which makes the process a daemon (fork() + setsid()
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* so that the process lives in the background, also opens /dev/console). It also provides the
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* close_file_descriptors() routine, which clears all file descriptors but 0, 1 and 2.
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*/
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/* PUBLIC API ************************************************************************************/
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/* daemonise()
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* Performs a fork() and setsid() so that the process lives in the background. It closes stdin,
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* stdout and stderr and opens /dev/null and/or /dev/console instead, as appropriate. On error,
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* this function exits the program.
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*/
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void daemonise(void);
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/* close_file_descriptors()
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* Closes all file descriptors but stdin, stdout and stderr. Should be called whether we are
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* daemonising or not.
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*/
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void close_file_descriptors(void);
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/* IMPLEMENTATION ********************************************************************************/
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void daemonise(void)
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{
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int fd;
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pid_t pid;
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/* close stdin and reopen it as /dev/null */
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TEMP_FAILURE_RETRY( close(STDIN_FILENO) );
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fd = open("/dev/null", O_RDONLY);
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switch(fd) {
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case -1:
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LOG(LOG_CRIT, "Could not open `/dev/null' (%m).");
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exit(1);
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case STDIN_FILENO:
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break;
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default:
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LOG(LOG_CRIT, "Opened `/dev/null' for stdin, but got file descriptor %d instead.", fd);
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exit(1);
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}
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/* close stdout and reopen it as /dev/console if possible, or /dev/null if not */
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TEMP_FAILURE_RETRY( close(STDOUT_FILENO) );
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fd = open("/dev/console", O_WRONLY | O_NOCTTY);
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if(fd == -1) {
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LOG(LOG_WARNING, "Could not open `/dev/console' for stdout (%m).");
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fd = open("/dev/null", O_WRONLY);
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}
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switch(fd) {
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case -1:
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LOG(LOG_CRIT, "Could not open `/dev/null' (%m).");
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exit(1);
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case STDOUT_FILENO:
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break;
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default:
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LOG(LOG_CRIT, "Opened `/dev/null' for stdout, but got file descriptor %d instead.", fd);
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exit(1);
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}
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/* close stderr and reopen it as /dev/console if possible, or /dev/null if not */
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TEMP_FAILURE_RETRY( close(STDERR_FILENO) );
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fd = open("/dev/console", O_WRONLY | O_NOCTTY);
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if(fd == -1) {
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LOG(LOG_WARNING, "Could not open `/dev/console' for stderr (%m).");
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/* force fd closed again, in case glibc kindly connected it to syslog for us */
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TEMP_FAILURE_RETRY( close(STDERR_FILENO) );
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fd = open("/dev/null", O_WRONLY);
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}
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switch(fd) {
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case -1:
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LOG(LOG_CRIT, "Could not open `/dev/null' (%m).");
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exit(1);
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case STDERR_FILENO:
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break;
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default:
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LOG(LOG_CRIT, "Opened `/dev/null' for stderr, but got file descriptor %d instead.", fd);
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exit(1);
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}
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/* daemonise */
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pid = fork();
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if(pid == (pid_t)-1) {
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LOG(LOG_CRIT, "Could not fork daemonised process (%m).");
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exit(1);
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}
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if(pid) {
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/* parent */
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_exit(0); /* don't call atexit() et al. in parent */
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}
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setsid();
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LOG(LOG_NOTICE, "Daemonised, PID %lu.", (unsigned long)getpid());
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}
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/* close_file_descriptors()
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* Adapted from libgslutil (GPL-3).
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*/
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void close_file_descriptors(void)
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{
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DIR* d;
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struct dirent* de;
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int i, end, dfd;
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d = opendir("/proc/self/fd");
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if(!d) {
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/* backup method */
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for(i = STDERR_FILENO + 1, end = getdtablesize(); i < end; ++i) {
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close(i);
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}
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return;
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}
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dfd = dirfd(d);
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while( (de = readdir(d)) ) {
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if(de->d_name[0] == '.') continue;
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i = strtol(de->d_name, 0, 10);
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if(i == dfd) continue; /* skip file descriptor associated with `DIR* d' */
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if(i <= STDERR_FILENO) continue; /* leave stdin, stdout, stderr alone */
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TEMP_FAILURE_RETRY( close(i) );
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}
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closedir(d);
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}
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/* options for text editors
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kate: replace-trailing-space-save true; space-indent true; tab-width 4;
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vim: expandtab:ts=4:sw=4
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*/
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@ -1,8 +1,8 @@
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/* daemonitor/src/daemonitor/600_run_program.c
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*
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* (c)2007, Laurence Withers, <l@lwithers.me.uk>.
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* Released under the GNU GPLv3. See file COPYING or
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* http://www.gnu.org/copyleft/gpl.html for details.
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* Copyright: ©2007–2012, Laurence Withers.
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* Author: Laurence Withers <l@lwithers.me.uk>
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* License: GPLv3
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*/
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@ -45,8 +45,8 @@ volatile int sigterm_received = 0;
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/* close_file_descriptors()
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* Closes all file descriptors but stdin, stdout and stderr. Should be called whether we are
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* daemonising or not.
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* Closes all file descriptors but stdin, stdout and stderr (which it leaves
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* unchanged).
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*/
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void close_file_descriptors(void);
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@ -56,6 +56,38 @@ void close_file_descriptors(void);
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/* close_file_descriptors()
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* Adapted from libgslutil (GPL-3).
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*/
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void
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close_file_descriptors(void)
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{
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DIR* d;
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struct dirent* de;
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int i, end, dfd;
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d = opendir("/proc/self/fd");
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if(!d) {
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/* backup method */
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for(i = STDERR_FILENO + 1, end = getdtablesize(); i < end; ++i) {
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close(i);
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}
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return;
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}
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dfd = dirfd(d);
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while( (de = readdir(d)) ) {
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if(de->d_name[0] == '.') continue;
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i = strtol(de->d_name, 0, 10);
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if(i == dfd) continue; /* skip file descriptor associated with `DIR* d' */
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if(i <= STDERR_FILENO) continue; /* leave stdin, stdout, stderr alone */
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TEMP_FAILURE_RETRY( close(i) );
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}
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closedir(d);
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}
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/* crash()
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* Crash the program. This is better than just calling exit() because it doesn't clean up. We
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* should leave our PID file lying around to look like we crashed. This function is paranoid.
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@ -113,6 +145,8 @@ void run_program(const char* exe_path, char** argv)
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/* child -- execute new process */
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if(pid == 0) {
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close_file_descriptors();
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/* clear the child's signal mask */
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sigemptyset(&ss);
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sigprocmask(SIG_SETMASK, &ss, 0);
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@ -203,6 +237,5 @@ void run_program(const char* exe_path, char** argv)
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/* options for text editors
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kate: replace-trailing-space-save true; space-indent true; tab-width 4;
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vim: expandtab:ts=4:sw=4
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*/
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@ -79,7 +79,7 @@ int main(int argc, char* argv[])
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{
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char* endp;
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const char* log_argument = 0, * pidfile_argument = 0, * restart_argument = 0;
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int daemon = 0, restart_interval = DEFAULT_RESTART_INTERVAL;
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int do_daemon = 0, restart_interval = DEFAULT_RESTART_INTERVAL;
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/* safety */
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close_file_descriptors(); /* leaves stdout etc. open */
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@ -91,7 +91,7 @@ int main(int argc, char* argv[])
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case '?': LOG_ANYWHERE("Invalid commandline options."); return 1;
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case 'h': usage(); return 1;
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case 'V': fputs("daemonitor " VERSION "\n", stderr); return 1;
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case 'd': ++daemon; break;
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case 'd': ++do_daemon; break;
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case 'l': log_argument = optarg; break;
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case 'p': pidfile_argument = optarg; break;
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case 'R': restart_argument = optarg; break;
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@ -136,7 +136,12 @@ int main(int argc, char* argv[])
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if(load_child_environ()) return 1;
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/* daemonise? */
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if(daemon) daemonise();
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if(do_daemon) {
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if(daemon(0, 0)) {
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LOG(LOG_CRIT, "daemon() failed: %m.");
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return 1;
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}
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}
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/* write a PID file */
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if(pidfile_argument) {
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