[refactor] Make aeternum usable programmatically.

aeternum.c

@@ -1,64 +1,64 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <stdio.h>
+#include <signal.h>
+#include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>
-#include <signal.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <assert.h>
+#include "aeternum.h"
 
+struct Options *aeternum_options(int argc, char *argv[]) {
+  Options *opts = Options_parse(argc, argv);
+  return opts;
+}
 
-void run_target(const char *name, char *args[]);
+void aeternum_start(Options *opts) {
+  assert(opts != NULL);
+  assert(opts->outfile != NULL);
+  assert(opts->errfile != NULL);
+  assert(opts->child_args);
+  aeternum_fork();
+  aeternum_redirect(opts->outfile, STDOUT_FILENO);
+  aeternum_redirect(opts->errfile, STDERR_FILENO);
+  aeternum_exec(opts->target, opts->child_args);
+}
 
-int main(int argc, char *argv[]) {
-  assert(argc > 1);
-  char **child_args = &argv[1];
-  int i;
+void aeternum_fork() {
 
-  // Fork the process.
   int pid = fork();
-
-  // fork() makes a clone of the current process - the same code will thus get
-  // executed in both the parent and the child.  We must check for this.
-  // fork() returns 0 in the child process, the child's pid in the parent
-  // process, and -1 if an error occurs while forking.
-
+
+  signal(SIGCHLD, SIG_IGN);
+  signal(SIGHUP, SIG_IGN);
+
   if (pid < 0) {
-    // An error has occurred
-    printf("An error has occurred while forking - errno %d.  Exiting.\n", errno);
+    printf("An error occurred: %s", strerror(errno));
+    // Should we find a graceful way to bail here?
     exit(pid);
   }
   else if (pid > 0) {
-    // This is the parent process
     printf("Child has been spawned and daemonized. PID: %d\n", pid);
-    // We want to daemonize, so the parent needs to exit at this point.
     exit(0);
   }
 
-  // Only child process can get here, parent process quits.
-
-  // Detach from the terminal; start a new process group
   setsid();
-
-  // Set the umask
   umask(027);
+}
 
-  // Redirect stdio to a file (only suitable if you want logging)
-  int out = open("out.log", O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IRGRP | S_IWGRP | S_IWUSR);
-  int err = open("err.log", O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IRGRP | S_IWGRP | S_IWUSR);
-  dup2(out, STDOUT_FILENO);
-  dup2(err, STDERR_FILENO);
-
-  // Ignore a few signals that could otherwise ruin our day.
-  signal(SIGCHLD, SIG_IGN);
-  signal(SIGHUP, SIG_IGN);
-
-  run_target(argv[1], child_args);
+void aeternum_redirect(const char *dest, int fileno) {
+  int out = open(dest,
+                  O_WRONLY | O_APPEND | O_CREAT,
+                  S_IRUSR | S_IRGRP | S_IWGRP | S_IWUSR);
+  if (out == -1) printf("An error occurred: %s", strerror(errno));
+  assert(out != -1);
+  int dup_res = dup2(out, fileno);
+  if (dup_res == -1) printf("An error occurred: %s", strerror(errno));
+  assert(dup_res != -1);
 }
 
-void run_target(const char *filename, char *args[]) {
-  int result;
-  result = execvp(filename, args);
+void aeternum_exec(const char *filename, char *args[]) {
+  int result = execvp(filename, args);
   assert(result != -1);
 }

aeternum.h

@@ -0,0 +1,16 @@
+#ifndef _aeternum_h
+#define _aeternum_h
+
+#include "options.h"
+
+struct Options *aeternum_options(int argc, char *argv[]);
+
+void aeternum_start(Options *opts);
+
+void aeternum_fork();
+
+void aeternum_redirect(const char *filename, int fileno);
+
+void aeternum_exec(const char *filename, char *args[]);
+
+#endif