From 4c1a3943bd8aa8de4fb420922caff5d14a8e8a28 Mon Sep 17 00:00:00 2001
From: Laurence Withers <lwithers@amethyst.lwithers.me.uk>
Date: Sat, 26 Jul 2008 17:24:19 +0000
Subject: [PATCH] Add run_program() implementation

---
 src/daemonitor/000_TopSource.c   |   1 +
 src/daemonitor/600_run_program.c | 138 +++++++++++++++++++++++++++++++
 src/daemonitor/999_main.c        |   2 +-
 3 files changed, 140 insertions(+), 1 deletion(-)
 create mode 100644 src/daemonitor/600_run_program.c

diff --git a/src/daemonitor/000_TopSource.c b/src/daemonitor/000_TopSource.c
index 782395c..a76b773 100644
--- a/src/daemonitor/000_TopSource.c
+++ b/src/daemonitor/000_TopSource.c
@@ -20,6 +20,7 @@
 #include <string.h>
 #include <syslog.h>
 #include <unistd.h>
+#include <sys/wait.h>
 #include <sys/types.h>
 
 /* options for text editors
diff --git a/src/daemonitor/600_run_program.c b/src/daemonitor/600_run_program.c
new file mode 100644
index 0000000..0325bf0
--- /dev/null
+++ b/src/daemonitor/600_run_program.c
@@ -0,0 +1,138 @@
+/* daemonitor/src/daemonitor/600_run_program.c
+ *
+ *  (c)2007, Laurence Withers, <l@lwithers.me.uk>.
+ *  Released under the GNU GPLv3. See file COPYING or
+ *  http://www.gnu.org/copyleft/gpl.html for details.
+*/
+
+
+
+/* PROGRAM EXECUTION AND MONITORING ROUTINES ******************************************************
+ *
+ *  This file provides the run_program() routine, which actually runs and waits on the child
+ *  process. `program_pid' is set to the PID of the child, which allows it to be sent signals.
+ */
+
+
+
+/* PUBLIC API ************************************************************************************/
+
+
+
+/* run_program()
+ *  Runs the program with the specified arguments. Logs the start and end of the process, including
+ *  exit status. Waits on the process to exit. A single call to this function is a single run. If
+ *  the program cannot be run, for whatever reason, that is logged and the function returns.
+ */
+void run_program(const char* exe_path, char** argv);
+
+
+
+/* close_file_descriptors()
+ *  Closes all file descriptors but stdin, stdout and stderr. Should be called whether we are
+ *  daemonising or not.
+ */
+void close_file_descriptors(void);
+
+
+
+/* IMPLEMENTATION ********************************************************************************/
+
+
+
+/* environ
+ *  As per environ(7), this variable must be declared by the user program. It is used to specify
+ *  the environment for our child process.
+ */
+extern char **environ;
+
+
+
+/* crash()
+ *  Crash the program. This is better than just calling exit() because it doesn't clean up. We
+ *  should leave our PID file lying around to look like we crashed. This function is paranoid.
+ */
+void crash(void) __attribute__((noreturn));
+void crash(void)
+{
+    /* raise SIGKILL; failing that, call abort(); failing that, _exit() */
+    raise(SIGKILL); /* quick + dirty + unblockable crash */
+    abort(); /* unblocks and raises SIGABRT */
+    _exit(127);
+}
+
+
+
+/* run_program()
+ *  fork() then wait(), logging the results of each step.
+ */
+void run_program(const char* exe_path, char** argv)
+{
+    pid_t pid;
+    siginfo_t si;
+
+    pid = fork();
+
+    /* deal with errors */
+    if(pid == (pid_t)-1) {
+        LOG(LOG_ERR, "Could not create new child process (%m).");
+        return;
+    }
+
+    /* child -- execute new process */
+    if(pid == 0) {
+        execve(exe_path, argv, environ);
+        LOG(LOG_ERR, "Could not execute `%s' (%m).", exe_path);
+        crash();
+    }
+
+    /* parent -- wait(2) on child */
+    LOG(LOG_NOTICE, "Created child process with PID %lu.", (unsigned long)pid);
+
+  wait_again:
+    /* wait on child */
+    si.si_pid = 0;
+    if(waitid(P_PID, pid, &si, WEXITED) == -1) {
+        switch(errno) {
+        case EINTR:
+            break; /* signal processed */
+
+        default:
+            LOG(LOG_ALERT, "waitid() returned error `%m' for PID %lu -- should not be possible.",
+                (unsigned long)pid);
+            crash();
+        }
+        goto wait_again; /* go again */
+    }
+
+    /* check that child did in fact exit */
+    if(si.si_pid != pid) {
+        LOG(LOG_ALERT, "waitid() returned results for PID %lu, but we were expecting %lu.",
+            (unsigned long)si.si_pid, (unsigned long)pid);
+        crash();
+    }
+
+    /* report how the child exited */
+    switch(si.si_code) {
+    case CLD_EXITED:
+        LOG(LOG_NOTICE, "Child process %lu exited with status %d.",
+            (unsigned long)pid, si.si_status);
+        break;
+
+    case CLD_KILLED:
+        LOG(LOG_NOTICE, "Child process %lu killed by signal %d (%s).",
+            (unsigned long)pid, si.si_status, strsignal(si.si_status));
+        break;
+
+    default:
+        LOG(LOG_WARNING, "Received si_code 0x%X from waitid(); ignoring it.", si.si_code);
+        goto wait_again;
+    }
+}
+
+
+
+/* options for text editors
+kate: replace-trailing-space-save true; space-indent true; tab-width 4;
+vim: expandtab:ts=4:sw=4
+*/
diff --git a/src/daemonitor/999_main.c b/src/daemonitor/999_main.c
index 2f26243..6616232 100644
--- a/src/daemonitor/999_main.c
+++ b/src/daemonitor/999_main.c
@@ -132,7 +132,7 @@ int main(int argc, char* argv[])
 
     /* run process */
     while(1) {
-        run_program(argv + optind, argc - optind);
+        run_program(argv[optind] /* path */, argv + optind + 1 /* argv[], null terminated */);
 
         if(restart_interval) {
             LOG(LOG_NOTICE, "Sleeping for %d seconds.", restart_interval);