The top level, which decides what is to be done and then carries this plan out.

§1. Inweb syntax has gradually shifted over the years, but there are two main versions: the second was cleaned up and simplified from the first in 2019.

int default_inweb_syntax = V2_SYNTAX;

§2. Inweb has a single fundamental mode of operation: on any given run, it is either tangling, weaving or analysing. These processes use the same input and parsing code, but then do very different things to produce their output, so the fork in the road is not met until halfway through Inweb's execution.

enum NO_MODE from 0  a special mode for doing nothing except printing command-line syntax
enum ANALYSE_MODE    for -scan, -catalogue, -functions and so on
enum TANGLE_MODE     for any form of -tangle
enum WEAVE_MODE      for any form of -weave
enum TRANSLATE_MODE  a special mode for translating a multi-web makefile
int fundamental_mode = NO_MODE;

§3. This operation will be applied to a single web, and will apply to the whole of that web unless we specify otherwise. Subsets of the web are represented by short pieces of text called "ranges". This can be a section range like 2/pine, a chapter number like 12, an appendix letter A or the preliminaries block P, the special chapter S for the "Sections" chapter of an unchaptered web, or the special value 0 to mean the entire web (which is the default).

When weaving in "swarm mode", however, the user chooses a multiplicity of operations rather than just one. Now it's no longer a matter of weaving a particular section or chapter: we can weave all of the sections or chapters, one after another.

enum SWARM_OFF_SWM from 0
enum SWARM_INDEX_SWM     make index(es) as if swarming, but don't actually swarm
enum SWARM_CHAPTERS_SWM  swarm the chapters
enum SWARM_SECTIONS_SWM  swarm the individual sections

§4. In order to run, Inweb needs to know where it is installed — this enables it to find its configuration file, the macros file, and so on. Unless told otherwise on the command line, we'll assume Inweb is present in the current working directory. The "materials" will then be in a further subfolder called Materials.

pathname *path_to_inweb = NULL;  where we are installed
pathname *path_to_inweb_materials = NULL;  the materials pathname
pathname *path_to_inweb_patterns = NULL;  where built-in patterns are stored

§5. We count the errors in order to be able to exit with a suitable exit code.

int no_inweb_errors = 0;
int verbose_mode = FALSE;

§6. Main routine.

int main(int argc, char **argv) {
    Initialise inweb6.1;
    inweb_instructions args = Configuration::read(argc, argv);
    verbose_mode = args.verbose_switch;
    fundamental_mode = args.inweb_mode;
    path_to_inweb = Pathnames::installation_path("INWEB_PATH", I"inweb");
    if (verbose_mode) {
        PRINT("Installation path is %p\n", path_to_inweb);
    path_to_inweb_patterns = Pathnames::down(path_to_inweb, I"Patterns");
    path_to_inweb_materials = Pathnames::down(path_to_inweb, I"Materials");


    Shut inweb down6.2;

§6.1. Initialise inweb6.1 =

    Foundation::start(argc, argv);

§6.2. Shut inweb down6.2 =

    return (no_inweb_errors == 0)?0:1;

§7. Following instructions. This is the whole program in a nutshell, and it's a pretty old-school program: some input, some thinking, a choice of three forms of output.

void Main::follow_instructions(inweb_instructions *ins) {
    web *W = NULL;
    if ((ins->chosen_web) || (ins->chosen_file)) {
        W = Reader::load_web(ins->chosen_web, ins->chosen_file,
            WebModules::make_search_path(ins->import_setting), TRUE);
        W->redirect_weaves_to = ins->weave_into_setting;
        Parser::parse_web(W, ins->inweb_mode);
    if (no_inweb_errors == 0) {
        if (ins->inweb_mode == TRANSLATE_MODE) Translate a makefile7.1
        else if (ins->show_languages_switch) List available programming languages7.2
        else if ((ins->test_language_setting) || (ins->test_language_on_setting)) Test a language7.3
        else if (ins->inweb_mode != NO_MODE) Analyse, tangle or weave an existing web7.4;

§7.1. This is a one-off featurette:

Translate a makefile7.1 =

    if ((ins->makefile_setting) && (ins->prototype_setting == NULL))
        ins->prototype_setting = Filenames::from_text(I"script.mkscript");
    if ((ins->gitignore_setting) && (ins->prototype_setting == NULL))
        ins->prototype_setting = Filenames::from_text(I"script.giscript");
    if ((ins->writeme_setting) && (ins->prototype_setting == NULL))
        ins->prototype_setting = Filenames::from_text(I"script.rmscript");
    if (ins->makefile_setting)
        Makefiles::write(W, ins->prototype_setting, ins->makefile_setting,
            WebModules::make_search_path(ins->import_setting), ins->platform_setting);
    else if (ins->gitignore_setting)
        Git::write_gitignore(W, ins->prototype_setting, ins->gitignore_setting);
    else if (ins->advance_setting)
    else if (ins->writeme_setting)
        Readme::write(ins->prototype_setting, ins->writeme_setting);

§7.2. As is this:

List available programming languages7.2 =


§7.3. And this:

Test a language7.3 =

    if ((ins->test_language_setting) && (ins->test_language_on_setting)) {
        Painter::colour_file(ins->test_language_setting, ins->test_language_on_setting,
            matter, coloured);
        PRINT("Test of colouring for language %S:\n%S\n%S\n",
            ins->test_language_setting->language_name, matter, coloured);
    } else {
        Errors::fatal("-test-language and -test-language-on must both be given");

§7.4. But otherwise we do something with the given web:

Analyse, tangle or weave an existing web7.4 =

    if (ins->inweb_mode != ANALYSE_MODE) Reader::print_web_statistics(W);
    if (ins->inweb_mode == ANALYSE_MODE) Analyse the web7.4.1;
    if (ins->inweb_mode == TANGLE_MODE) Tangle the web7.4.2;
    if (ins->inweb_mode == WEAVE_MODE) Weave the web7.4.3;

§7.4.1. "Analysis" invokes any combination of the following diagnostic tools:

Analyse the web7.4.1 =

    if (ins->swarm_mode != SWARM_OFF_SWM)
        Errors::fatal("only specific parts of the web can be analysed");
    if (ins->catalogue_switch)
        Analyser::catalogue_the_sections(W, ins->chosen_range, BASIC_SECTIONCAT);
    if (ins->functions_switch)
        Analyser::catalogue_the_sections(W, ins->chosen_range, FUNCTIONS_SECTIONCAT);
    if (ins->structures_switch)
        Analyser::catalogue_the_sections(W, ins->chosen_range, STRUCTURES_SECTIONCAT);
    if (ins->makefile_setting)
        Analyser::write_makefile(W, ins->makefile_setting,
            WebModules::make_search_path(ins->import_setting), ins->platform_setting);
    if (ins->gitignore_setting)
        Analyser::write_gitignore(W, ins->gitignore_setting);
    if (ins->advance_switch)
    if (ins->scan_switch)
        Analyser::scan_line_categories(W, ins->chosen_range);

§7.4.2. We can tangle to any one of what might be several targets, numbered upwards from 0. Target 0 always exists, and is the main program forming the web. For many webs, this will in fact be the only target, but Inweb also allows marked sections of a web to be independent targets — the idea here is to allow an Appendix in the web to contain a configuration file, or auxiliary program, needed for the main program to work; this might be written in a quite different language from the rest of the web, and tangles to a different output, but needs to be part of the web since it's essential to an understanding of the whole system.

In this section we determine tn, the target number wanted, and tangle_to, the filename of the tangled code to write. This may have been set at the command line , but otherwise we impose a sensible choice based on the target.

Tangle the web7.4.2 =

    tangle_target *tn = NULL;
    if (Str::eq_wide_string(ins->chosen_range, L"0")) {
        Work out main tangle destination7.4.2.1;
    } else if (Reader::get_section_for_range(W, ins->chosen_range)) {
        Work out an independent tangle destination, from one section of the web7.4.2.2;
    if (Str::len(tangle_leaf) == 0) { Errors::fatal("no tangle destination known"); }

    filename *tangle_to = ins->tangle_setting;
    if (tangle_to == NULL) {
        pathname *P = Reader::tangled_folder(W);
        if (W->md->single_file) P = Filenames::up(W->md->single_file);
        tangle_to = Filenames::in(P, tangle_leaf);
    if (tn == NULL) tn = Tangler::primary_target(W);
    Tangler::tangle(W, tn, tangle_to);
    if (ins->ctags_switch) Ctags::write(W, ins->ctags_setting);

§ Here the target number is 0, and the tangle is of the main part of the web, which for many small webs will be the entire thing.

Work out main tangle destination7.4.2.1 =

    tn = NULL;
    if (Bibliographic::data_exists(W->md, I"Short Title"))
        Str::copy(tangle_leaf, Bibliographic::get_datum(W->md, I"Short Title"));
        Str::copy(tangle_leaf, Bibliographic::get_datum(W->md, I"Title"));
    Str::concatenate(tangle_leaf, W->main_language->file_extension);

§ If someone tangles, say, 2/eg then the default filename is "Example Section".

Work out an independent tangle destination, from one section of the web7.4.2.2 =

    section *S = Reader::get_section_for_range(W, ins->chosen_range);
    tn = S->sect_target;
    if (tn == NULL) Errors::fatal("section cannot be independently tangled");
    Str::copy(tangle_leaf, Filenames::get_leafname(S->md->source_file_for_section));

§7.4.3. Weaving is not actually easier, it's just more thoroughly delegated:

Weave the web7.4.3 =


    theme_tag *tag = Tags::find_by_name(ins->tag_setting, FALSE);
    if ((Str::len(ins->tag_setting) > 0) && (tag == NULL))
        Errors::fatal_with_text("no such theme as '%S'", ins->tag_setting);

    weave_pattern *pattern = Patterns::find(W, ins->weave_pattern);
    if ((ins->chosen_range_actually_chosen == FALSE) && (ins->chosen_file == NULL))
        Configuration::set_range(ins, pattern->default_range);

    int r = Formats::begin_weaving(W, pattern);
    if (r != SWARM_OFF_SWM) ins->swarm_mode = r;
    Assign section numbers for printing purposes7.4.3.1;
    if (ins->swarm_mode == SWARM_OFF_SWM) {
        Swarm::weave_subset(W, ins->chosen_range, FALSE, tag, pattern,
            ins->weave_to_setting, ins->weave_into_setting,
            ins->breadcrumb_setting, ins->navigation_setting);
    } else {
        Swarm::weave(W, ins->chosen_range, ins->swarm_mode, tag, pattern,
            ins->weave_to_setting, ins->weave_into_setting,
            ins->breadcrumb_setting, ins->navigation_setting);
    Formats::end_weaving(W, pattern);

§ Assign section numbers for printing purposes7.4.3.1 =

    section *S; int k = 1;
    LOOP_OVER(S, section)
        if (Reader::range_within(S->md->sect_range, ins->chosen_range))
            S->printed_number = k++;

§8. Error messages. The Foundation module provides convenient functions to issue error messages, but we'll use the following wrapper when issuing an error at a line of web source:

void Main::error_in_web(text_stream *message, source_line *sl) {
    if (sl) {
        Errors::in_text_file_S(message, &(sl->source));
        WRITE_TO(STDERR, "%07d  %S\n", sl->source.line_count, sl->text);
    } else {
        Errors::in_text_file_S(message, NULL);