BT_INPUT(1)

💖 BT_INPUT(1) — the btparse input/parsing functions, bestie edition 💖

okay so this is the bt_input page from the btparse manual, and it's literally all about the functions that read and parse BibTeX data — turning raw text into abstract-syntax trees (ASTs) ✨ no cap, that's the whole vibe.

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🌸 SYNOPSIS 🌸

void  bt_set_stringopts (bt_metatype_t metatype, btshort options);
AST * bt_parse_entry_s (char *    entry_text,
                        char *    filename,
                        int       line,
                        btshort    options,
                        boolean * status);
AST * bt_parse_entry   (FILE *    infile,
                        char *    filename,
                        btshort    options,
                        boolean * status);
AST * bt_parse_file    (char *    filename,
                        btshort    options,
                        boolean * overall_status);

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🦋 DESCRIPTION 🦋

So the functions on this page are the ones that read and parse BibTeX data, converting it from raw text into abstract-syntax trees, aka ASTs. Glow-up from string to tree, honestly 💅

💜 bt_set_stringopts ()

void bt_set_stringopts (bt_metatype_t metatype, btshort options);

This one sets the string-processing options for a particular entry metatype. It affects the entry post-processing that bt_parse_entry_s(), bt_parse_entry(), and bt_parse_file() do. And if you never call bt_set_stringopts() at all, then the four metatypes default to these sets of string options:

BTE_REGULAR    BTO_CONVERT | BTO_EXPAND | BTO_PASTE | BTO_COLLAPSE
BTE_COMMENT    0
BTE_PREAMBLE   0
BTE_MACRODEF   BTO_CONVERT | BTO_EXPAND | BTO_PASTE

Like, for example:

bt_set_stringopts (BTE_COMMENT, BTO_COLLAPSE);

will cause the library to collapse whitespace in the value from all comment entries — and the AST returned by one of the bt_parse_* functions will reflect that change. periodt ✨

🎀 bt_parse_entry ()

AST * bt_parse_entry (FILE *    infile,
                      char *    filename,
                      btshort    options,
                      boolean * status);

Scans and parses the next BibTeX entry in infile. You should supply filename to help btparse generate accurate error messages; the library keeps track of infile's current line number internally, so you don't need to pass that in, no worries bestie 🫶 options should be a bitmap of non-string-processing options (currently, BTO_NOSTORE to disable storing macro expansions is the only such option). *status will be set to TRUE if the entry parsed successfully or with only minor warnings, and FALSE if there were any serious lexical or syntactic errors. If status is NULL, then the parse status will be unavailable to you. Both minor warnings and serious errors are reported on stderr.

Returns a pointer to the abstract-syntax tree (AST) describing the entry just parsed, or NULL if no more entries were found in infile — and that will leave infile at end-of-file. Do not attempt to second guess bt_parse_entry() by detecting end-of-file yourself 😤 it must be allowed to determine this on its own so it can clean up some static data that is preserved between calls on the same file.

🚨 bt_parse_entry() has two important restrictions that you should know about. First, you should let btparse manage all the input on the file. This is for reasons both superficial — so the library knows the current line number in order to generate accurate error messages — and fundamental — the library must be allowed to detect end-of-file in order to clean up certain static variables and allow you to parse another file. Second, you cannot interleave the parsing of two different files. Attempting to do so will result in a fatal error that will crash your program 💀 This is a direct result of the static state maintained between calls of bt_parse_entry().

Because of two distinct "failures" possible for bt_parse_entry() (end-of-file, which is expected but means to stop processing the current file; and error-in-input, which is not expected but allows you to continue processing the same file), you should usually call it like this:

while (entry = bt_parse_entry (file, filename, options, &ok))
{
   if (ok)
   {
      /* ... process entry ... */
   }
}

At the end of this loop, feof (file) will be true. iconic behavior tbh 👑

🌈 bt_parse_entry_s ()

AST * bt_parse_entry_s (char *    entry_text,
                        char *    filename,
                        int       line,
                        btshort    options,
                        boolean * status)

Scans and parses a single complete BibTeX entry contained in a string, entry_text. If you read this string from a file, you should help btparse generate accurate error messages by supplying the name of the file as filename and the line number of the beginning of the entry as line; otherwise, set filename to NULL and line to 1. options and status are the same as for bt_parse_entry().

Returns a pointer to the abstract-syntax tree (AST) describing the entry just parsed, and NULL if no entries were found in entry_text or if entry_text was NULL.

Now listen — you should call bt_parse_entry_s() once more than the total number of entries you wish to parse 🙈 On the final call, set entry_text to NULL so the function knows there's no more text to parse. This final call is what lets it clean up some structures allocated on the first call. So bt_parse_entry_s() is usually used like this:

char *  entry_text;
btshort  options = 0;
boolean ok;
AST *   entry_ast;

while (entry_text = get_more_text ())
{
   entry_ast = bt_parse_entry_s (entry_text, NULL, 1, options, &ok);
   if (ok)
   {
      /* ... process entry ... */
   }
}

bt_parse_entry_s (NULL, NULL, 1, options, NULL);    /* cleanup */

assuming that get_more_text() returns a pointer to the text of an entry to parse, or NULL if there's no more text available. that cleanup call is the main character of the function, lowkey 🧚

⭐ bt_parse_file ()

AST * bt_parse_file (char *    filename,
                     btshort    options,
                     boolean * status)

Scans and parses an entire BibTeX file 🎉 If filename is NULL or -, then stdin will be read; otherwise, it attempts to open the named file. If this attempt fails, it prints an error message to stderr and returns NULL. options and status are the same as for bt_parse_entry() — and note that *status will be FALSE if there were any errors in the entire file; for finer granularity of error-checking, you should use bt_parse_entry() instead.

Returns a pointer to a linked list of ASTs representing the entries in the file, or NULL if no entries were found in the file. This list can be traversed with bt_next_entry(), and the individual entries then traversed as usual (see bt_traversal). a whole linked list?? we love a collection 💖

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🔥 SEE ALSO 🔥

btparse, bt_postprocess, bt_traversal

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👑 AUTHOR 👑

Greg Ward <gward@python.net>

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and that's the page, bestie!! 🍓💜 it's btparse, version 0.91, dated 2025-09-04, and yes that footer totally deserved its own little moment at the end of the manual page 🎀✨ slay.