Add ability to override environment variables for child process

src/daemonitor/500_env.c

@@ -0,0 +1,155 @@
+/* daemonitor/src/daemonitor/500_env.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.
+*/
+
+
+
+/* ENVIRONMENT HANDLING ***************************************************************************
+ *
+ *  This file contains routines for modifying the environment of the child process.
+ */
+
+
+
+/* PUBLIC API ************************************************************************************/
+
+
+
+/* set_environment_file()
+ *  Stores a pointer to a filename from which the environment is loaded. A pointer to the string
+ *  is stored; the string itself is not copied.
+ */
+void set_environment_file(const char* filename);
+
+
+
+/* child_environ
+ *  Set by load_child_environ(), this is the list of enviroment vairables loaded from the file
+ *  specified by set_environment_file(), in a format suitable for execve(2).
+ */
+extern char** child_environ;
+
+
+
+/* load_child_environ()
+ *  Opens and parses the environment file whose name is provided by set_environment_file(), storing
+ *  the results in `child_environ' (which is cleared first if necessary). On error, logs the
+ *  reason, and returns -1. Returns 0 on success. If no environment file has been set, child_environ
+ *  is instead set to point at `environ' and 0 is returned.
+ */
+int load_child_environ(void);
+
+
+
+/* IMPLEMENTATION ********************************************************************************/
+
+
+
+/* environ_filename, set_environment_file()
+ *  The filename of the environment file. If 0, then no file has been specified. The function
+ *  simply stores the pointer.
+ */
+const char* environ_filename = 0;
+void set_environment_file(const char* filename)
+{
+    environ_filename = filename;
+}
+
+
+
+/* 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;
+
+
+
+/* child_environ et al.
+ *  Dynamic array of allocated strings.
+ */
+char** child_environ = 0;
+int child_environ_num = 0, child_environ_size = 0;
+
+
+
+/* add_child_environ_entry()
+ *  Add a pointer `p' into the dynamic array `child_environ'.
+ */
+void add_child_environ_entry(char* p)
+{
+    char** n;
+
+    if(child_environ_num == child_environ_size) {
+        child_environ_size = child_environ_size ? (child_environ_size << 1) : 16;
+        n = realloc(child_environ, child_environ_size * sizeof(char*));
+        if(!n) {
+            LOG(LOG_WARNING, "Out of memory (%d environment variables).", child_environ_size);
+            return;
+        }
+        child_environ = n;
+    }
+
+    child_environ[child_environ_num++] = p;
+}
+
+
+
+/* load_child_environ()
+ *  If `environ_filename' is 0, simply point `child_environ' at libc's `environ' and return with
+ *  success. Otherwise, load the file, storing its lines into the dynamic array `child_environ'.
+ */
+int load_child_environ(void)
+{
+    int i;
+    FILE* fp;
+    char* line;
+    size_t line_sz;
+    ssize_t ret;
+
+    /* don't override */
+    if(!environ_filename) {
+        child_environ = environ;
+        return 0;
+    }
+
+    /* clear old array entries */
+    for(i = 0; i < child_environ_num; ++i) {
+        free(child_environ[i]);
+    }
+    child_environ_num = 0;
+
+    /* open file */
+    fp = fopen(environ_filename, "r");
+    if(!fp) {
+        LOG(LOG_ERR, "Could not open environment file `%s' (%m).", environ_filename);
+        return -1;
+    }
+
+    /* store each line */
+    while(1) {
+        line = 0;
+        line_sz = 0;
+        ret = getline(&line, &line_sz, fp);
+        if(ret == -1) break; /* EOF */
+        if(ret < 2) continue; /* skip blank lines */
+
+        if(line[ret - 1] == '\n') line[ret - 1] = 0; /* strip `\n' */
+        add_child_environ_entry(line);
+    }
+
+    /* clean up */
+    fclose(fp);
+    add_child_environ_entry(0);
+    return 0;
+}
+
+
+
+/* options for text editors
+kate: replace-trailing-space-save true; space-indent true; tab-width 4;
+vim: expandtab:ts=4:sw=4
+*/

src/daemonitor/600_run_program.c

@@ -40,14 +40,6 @@ void close_file_descriptors(void);
 
 
 
-/* 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.
@@ -81,7 +73,7 @@ void run_program(const char* exe_path, char** argv)
 
     /* child -- execute new process */
     if(pid == 0) {
-        execve(exe_path, argv, environ);
+        execve(exe_path, argv, child_environ);
         LOG(LOG_ERR, "Could not execute `%s' (%m).", exe_path);
         crash();
     }

src/daemonitor/999_main.c

@@ -35,6 +35,8 @@ void usage(void)
         " -R, --restart-interval <i>   Sets the length of time between the process\n"
         "                              exiting and being restarted, in seconds (default\n"
         "                              " DEFAULT_RESTART_INTERVAL_S "). May be 0 to restart immediately.\n"
+        " -E, --environment <path>  Name of file containing environment variables for\n"
+        "                           child process, one NAME=VALUE entry per line.\n"
     "", stderr);
 }
 
@@ -50,6 +52,7 @@ struct option options[] = {
     { "log", required_argument, 0, 'l' },
     { "pidfile", required_argument, 0, 'p' },
     { "restart-interval", required_argument, 0, 'R' },
+    { "environment", required_argument, 0, 'E' },
     { 0, 0, 0, 0 }
 };
 
@@ -58,7 +61,7 @@ struct option options[] = {
 /* optstr
  *  The list of short commandline options for getopt(3). Sorted alphabetically, lowercase first.
  */
-const char* optstr = "dhl:p:R:V";
+const char* optstr = "dhl:p:E:R:V";
 
 
 
@@ -86,6 +89,7 @@ int main(int argc, char* argv[])
         case 'l': log_argument = optarg; break;
         case 'p': pidfile_argument = optarg; break;
         case 'R': restart_argument = optarg; break;
+        case 'E': set_environment_file(optarg); break;
         }
     }
   opts_done:
@@ -120,6 +124,9 @@ int main(int argc, char* argv[])
         log_destination_set(log_destination_file);
     }
 
+    /* set up environment */
+    if(load_child_environ()) return 1;
+
     /* daemonise? */
     if(daemon) daemonise();