load argv[1] as script and remove default paths

doc/riverguile.1

@@ -7,6 +7,7 @@ riverguile \- scheme powered scripting layer for river
 .
 .SH SYNOPSIS
 .SY riverguile
+path-to-script
 .YS
 .
 .
@@ -17,20 +18,29 @@ Scripting layer for the
 Wayland server.
 Allows the user to send commands to the Wayland server (probably river) and
 install handlers for events from a scheme script.
+The sheme implementation is provided by
+.BR guile (1).
 .P
-By default, riverguile will exit after the script has been loaded and evaluated.
+The canonical way to use riverguile is as an interpreter for the river init
-If certain handlers are installed it will run continously.
+script.
+To do so place the following expression at the very top of your init script:
 .P
-Uppon launch, riverguile tries to load the script from the following paths
+.RS
-in the given order:
+.EX
-.IP \(bu 2
+#!/bin/env riverguile
-\fBlayout.scm\fR
+!#
-.IP \(bu 2
+.EE
-\fB$XDG_CONFIG_HOME/river/layout.scm\fR
+.RE
-.IP \(bu 2
+.P
-\fB$HOME/.config/river/layout.scm\fR
+Do not leave out the second line, as the octothorpe plus exlamation-mark
-.IP \(bu 2
+combination indicates a multi-line comment in scheme.
-\fB/etc/riverguile/layout.scm\fR
+Do not forget to mark your init script as executable.
+Your custom scheme code to configure the river session may follow after these
+two lines.
+.P
+By default, riverguile will exit after the script has been loaded.
+However if certain handlers are installed it will run continously to provide
+that functionality.
 .
 .
 .SH COMMANDS

src/riverguile.c

@@ -255,79 +255,69 @@ static char *formatted_buffer (const char *fmt, ...)
 	return buffer;
 }
 
-static char *get_script_path (void)
+static char *get_script_path (char *relative_path)
 {
-	struct {
+	assert(relative_path != NULL);
-		const char *fmt;
-		bool needs_env;
-		const char *env;
-	} paths[] = {
-		{ .fmt = "layout.scm",                       .needs_env = false, .env = NULL                      },
-		{ .fmt = "%s/riverguile/layout.scm",         .needs_env = true,  .env = getenv("XDG_CONFIG_HOME") },
-		{ .fmt = "%s/river/layout.scm",              .needs_env = true,  .env = getenv("XDG_CONFIG_HOME") },
-		{ .fmt = "%s/.config/riverguile/layout.scm", .needs_env = true,  .env = getenv("HOME")            },
-		{ .fmt = "%s/.config/river/layout.scm",      .needs_env = true,  .env = getenv("HOME")            },
-		{ .fmt = "/etc/riverguile/layout.scm",       .needs_env = false, .env = NULL                      }
-	};
 
 	char *path = NULL;
-	for (size_t i = 0; i < (sizeof(paths) / sizeof(paths[0])); i++)
+	if ( relative_path[0] == '/' )
+		path = formatted_buffer("%s", relative_path);
+	else
 	{
-		if ( path != NULL )
+		/* When scm_primitive_load_path() receives a relative path, it
+		 * tries to look it up in the guile module path. So we must
+		 * always provide it an absolute path.
+		 */
+		char buffer[4 * 1024];
+		char *cwd = getcwd(buffer, 4 * 1024);
+		if ( cwd == NULL )
 		{
-			free(path);
+			fprintf(stderr, "ERROR: getcwd: %s\n", strerror(errno));
-			path = NULL;
-		}
-
-		/* Path needs env var, but it is not set. */
-		if ( paths[i].needs_env && paths[i].env == NULL )
-			continue;
-
-		path = formatted_buffer(paths[i].fmt, paths[i].env);
-		if ( path == NULL )
-			return NULL;
-
-		/* Does the path exist? */
-		if ( access(path, F_OK) != 0 )
-			continue;
-
-		/* Is it readable? */
-		if ( access(path, R_OK) != 0 )
-		{
-			fprintf(stderr, "ERROR: Script '%s' exists, but is not readable.\n", path);
-			free(path);
 			return NULL;
 		}
 
-		return path;
+		path = formatted_buffer("%s/%s", cwd, relative_path);
+	}
+	if ( path == NULL )
+		return NULL;
+
+	if ( access(path, R_OK) != 0 )
+	{
+		fprintf(stderr, "ERROR: Script '%s' is not readable.\n", path);
+		free(path);
+		return NULL;
 	}
 
-	if ( path != NULL )
+	return path;
-		free(path);
-
-	fputs("ERROR: No script found.\n", stderr);
-	return NULL;
 }
 
-int main(int argc, char *argv[])
+int main (int argc, char *argv[])
 {
+	if ( argc != 2
+		|| strcmp(argv[1], "--help") == 0
+		|| strcmp(argv[1], "-h") == 0
+		|| strcmp(argv[1], "-?") == 0 )
+	{
+		fprintf(stderr, "USAGE: %s path-to-script\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
 	fputs("INFO: Welcome to riverguile!\n", stderr);
 
 	signal(SIGSEGV, handle_error);
 	signal(SIGFPE, handle_error);
 	signal(SIGINT, handle_interrupt);
 
-	wl_list_init(&context.outputs);
+	context.path = get_script_path(argv[1]);
-	wl_list_init(&context.seats);
-
-	// TODO use argv[1] if present
-	context.path = get_script_path();
 	if ( context.path == NULL )
 	{
 		context.ret = EXIT_FAILURE;
 		goto early_exit;
 	}
-	fprintf(stderr, "INFO: Found script: %s\n", context.path);
+	fprintf(stderr, "INFO: Using script: %s\n", context.path);
+
+	wl_list_init(&context.outputs);
+	wl_list_init(&context.seats);
 
 	/* We query the display name here instead of letting wl_display_connect()
 	 * figure it out itself, because libwayland (for legacy reasons) falls