Lexical analysis is the grouping of consecutive characters into units, called tokens , that are meaningful in a particular language. Parsing is the processing of the lexical analysis token sequence to verify that tokens appear in an order permitted by the language rules, called the grammar . Semantic analysis, or code generation, is the interpretation of a grammar-conformant token stream to perform an intended task. The only output normally produced by bibparse is on the standard error unit, stderr , and then only if grammatical errors are detected.
Silent execution means a successful parse.
The program exit code is zero on a successful parse, and non-zero otherwise. Otherwise, it is assumed to be a BibTeX file. If you are puzzled by an error message reported by bibparse , you are advised to extract the BibTeX entry at, and possibly, immediately preceding, the line number in the diagnostic, then save that data in a temporary file and run bibparse -d on that small file, so as not to be overwhelmed by the output. Nonterminals, which are intermediate stages in the grammar processing, are spelled in lowercase letters. Each nonterminal referred to in the grammar eventually defines a grammar rule, which takes the form of a nonterminal, a colon, and one or more alternative expansions, separated by a vertical bar.