compress: Overhaul the meaning of --aggressiveness.

[paraslash.git] / daemon.c

diff --git a/daemon.c b/daemon.c
index 7c625bbea9d84c5ac9b37a22253346576cbb7183..bfa81487430f62dc7417db6ba6e0c6d53c008051 100644 (file)
--- a/daemon.c
+++ b/daemon.c
@@ -1,8 +1,4 @@
-/*
- * Copyright (C) 1997 Andre Noll <maan@tuebingen.mpg.de>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* Copyright (C) 1997 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
 
 /** \file daemon.c Some helpers for programs that detach from the console. */
 
@@ -34,6 +30,13 @@ struct daemon {
        char *hostname;
        /** Used for colored log messages. */
        char log_colors[NUM_LOGLEVELS][COLOR_MAXLEN];
+       char *old_cwd;
+       /*
+        * If these pointers are non-NULL, the functions are called from
+        * daemon_log() before and after writing each log message.
+        */
+       void (*pre_log_hook)(void);
+       void (*post_log_hook)(void);
 };
 
 static struct daemon the_daemon, *me = &the_daemon;
@@ -121,7 +124,12 @@ void daemon_set_logfile(const char *logfile_name)
 {
        free(me->logfile_name);
        me->logfile_name = NULL;
-       if (logfile_name)
+       if (!logfile_name)
+               return;
+       if (me->old_cwd && logfile_name[0] != '/')
+               me->logfile_name = make_message("%s/%s", me->old_cwd,
+                       logfile_name);
+       else
                me->logfile_name = para_strdup(logfile_name);
 }
 
@@ -138,6 +146,12 @@ void daemon_set_loglevel(const char *loglevel)
        me->loglevel = ret;
 }
 
+void daemon_set_hooks(void (*pre_log_hook)(void), void (*post_log_hook)(void))
+{
+       me->pre_log_hook = pre_log_hook;
+       me->post_log_hook = post_log_hook;
+}
+
 /**
  * Set one of the daemon config flags.
  *
@@ -155,10 +169,6 @@ static bool daemon_test_flag(unsigned flag)
        return me->flags & flag;
 }
 
-static void dummy_sighandler(__a_unused int s)
-{
-}
-
 /**
  * Do the usual stuff to become a daemon.
  *
@@ -166,33 +176,46 @@ static void dummy_sighandler(__a_unused int s)
  *
  * Fork, become session leader, cd to /, and dup fd 0, 1, 2 to /dev/null. If \a
  * parent_waits is false, the parent process terminates immediately.
- * Otherwise, it calls pause() to sleep until it receives \p SIGTERM or \p
- * SIGCHLD and exits successfully thereafter. This behaviour is useful if the
- * daemon process should not detach from the console until the child process
- * has completed its setup.
+ * Otherwise, a pipe is created prior to the fork() and the parent tries to
+ * read a single byte from the reading end of the pipe. The child is supposed
+ * to write to the writing end of the pipe after it completed its setup
+ * procedure successfully. This behaviour is useful to let the parent process
+ * die with an error if the child process aborts early, since in this case the
+ * read() will return non-positive.
+ *
+ * \return This function either succeeds or calls exit(3). If parent_waits is
+ * true, the return value is the file descriptor of the writing end of the
+ * pipe. Otherwise the function returns zero.
  *
  * \sa fork(2), setsid(2), dup(2), pause(2).
  */
-void daemonize(bool parent_waits)
+int daemonize(bool parent_waits)
 {
        pid_t pid;
-       int null;
+       int null, pipe_fd[2];
 
-       PARA_INFO_LOG("daemonizing\n");
+       if (parent_waits && pipe(pipe_fd) < 0)
+               goto err;
+       PARA_INFO_LOG("subsequent log messages go to %s\n", me->logfile_name?
+                me->logfile_name : "/dev/null");
        pid = fork();
        if (pid < 0)
                goto err;
-       if (pid) {
+       if (pid) { /* parent exits */
                if (parent_waits) {
-                       signal(SIGTERM, dummy_sighandler);
-                       signal(SIGCHLD, dummy_sighandler);
-                       pause();
+                       char c;
+                       close(pipe_fd[1]);
+                       exit(read(pipe_fd[0], &c, 1) <= 0?
+                               EXIT_FAILURE : EXIT_SUCCESS);
                }
-               exit(EXIT_SUCCESS); /* parent exits */
+               exit(EXIT_SUCCESS);
        }
+       if (parent_waits)
+               close(pipe_fd[0]);
        /* become session leader */
        if (setsid() < 0)
                goto err;
+       me->old_cwd = getcwd(NULL, 0);
        if (chdir("/") < 0)
                goto err;
        null = open("/dev/null", O_RDWR);
@@ -205,7 +228,7 @@ void daemonize(bool parent_waits)
        if (dup2(null, STDERR_FILENO) < 0)
                goto err;
        close(null);
-       return;
+       return parent_waits? pipe_fd[1] : 0;
 err:
        PARA_EMERG_LOG("fatal: %s\n", strerror(errno));
        exit(EXIT_FAILURE);
@@ -230,15 +253,18 @@ void daemon_close_log(void)
  */
 void daemon_open_log_or_die(void)
 {
-       daemon_close_log();
+       FILE *new_log;
+
        if (!me->logfile_name)
                return;
-       me->logfile = fopen(me->logfile_name, "a");
-       if (!me->logfile) {
+       new_log = fopen(me->logfile_name, "a");
+       if (!new_log) {
                PARA_EMERG_LOG("can not open %s: %s\n", me->logfile_name,
                        strerror(errno));
                exit(EXIT_FAILURE);
        }
+       daemon_close_log();
+       me->logfile = new_log;
        /* equivalent to setlinebuf(), but portable */
        setvbuf(me->logfile, NULL, _IOLBF, 0);
 }
@@ -366,8 +392,6 @@ time_t daemon_get_uptime(const struct timeval *current_time)
  * \param current_time See a \ref daemon_get_uptime().
  *
  * \return A dynamically allocated string of the form "days:hours:minutes".
- *
- * \sa server_uptime.
  */
 __malloc char *daemon_get_uptime_str(const struct timeval *current_time)
 {
@@ -397,6 +421,8 @@ __printf_2_3 void daemon_log(int ll, const char* fmt,...)
                return;
 
        fp = me->logfile? me->logfile : stderr;
+       if (me->pre_log_hook)
+               me->pre_log_hook();
        color = daemon_test_flag(DF_COLOR_LOG)? me->log_colors[ll] : NULL;
        if (color)
                fprintf(fp, "%s", color);
@@ -429,4 +455,6 @@ __printf_2_3 void daemon_log(int ll, const char* fmt,...)
        va_end(argp);
        if (color)
                fprintf(fp, "%s", COLOR_RESET);
+       if (me->post_log_hook)
+               me->post_log_hook();
 }