Fawk - datasheet

Language characteristics

Fawk is an AWK dialect.

Fawk is an imperative programming language. Libfawk implements a compiler and a custom VM as a tiny, as a reentrant ANSI/C89 library.

Fawk supports:

• the common awk features: variables, functions, if(), for(), do-while, while()
• data types: NIL, number (normally double precision floating point), string and function reference
• arrays indexed with any type (implemented as hash table)
• array-in-array
• for(in) for iterating over the members of an array; the body of the loop may change the array
• fake multi-dimensional arrays using the usual AWK trick of SUBSEP
• an alternate struct-like array syntax
• include for including other fawk sources
• variable argument (vararg) functions
• text-block, a multiline template-like string "literal" type with expression inserts

What fawk does not have compared to standard awk

• I/O: no getline, no print, no redirections (the host application may provide these through functions)
• input processing: no BEGIN, no END, no pattern matches, only functions
• field splitting: there's no $0, $1, NF, IFS, OFS
• most builtin awk standard functions (regex, math) are missing: the host application may define them
• historical syntax corner cases: there's no function call without (), no invisible string concatenation operator
• no liberal policy on semicolons: a statement must be terminated with a semicolon (it's like in C)
• no break or continue statement in loops (yet?)

What extras fawk offers over standard awk

• support for the include keyword (requires a few lines of host application support)
• support for array-in-array
• support for alternative array syntax of arr.idx for using array as struct
• functions are first-class objects: references to functions can be stored in variables and arrays, they also can be passed as function arg
• explicit operator @ for string concatenation
• array references can be compared for figuring if they are referring to the same array
• isarray() builtin and optional explicit A[] array declarator; whether function parameters are arrays are determined runtime: it is possible to write a function that accepts either array or scalar