GAWK: Effective AWK Programming

Glossary 307BBSBitSee “Bulletin Board System.”Short for “Binary Digit.” All values in computer memory ultimately reduceto binary digits: values that are either zero or one. Groups of bits may beinterpreted differently—as integers, floating-point numbers, character data, addressesof other memory objects, or other data. awk lets you work with floatingpointnumbers and strings. gawk lets you manipulate bit values with the builtinfunctions described in Section 8.1.6 [Bit-Manipulation Functions of gawk],page 150.Computers are often defined by how many bits they use to represent integervalues. Typical systems are 32-bit systems, but 64-bit systems are becomingincreasingly popular, and 16-bit systems are waning in popularity.Boolean ExpressionNamed after the English mathematician Boole. See also “Logical Expression.”Bourne ShellThe standard shell (‘/bin/sh’) on Unix and Unix-like systems, originally writtenby Steven R. Bourne. Many shells (bash, ksh, pdksh, zsh) are generallyupwardly compatible with the Bourne shell.Built-in FunctionThe awk language provides built-in functions that perform various numerical,I/O-related, and string computations. Examples are sqrt (for the square rootof a number) and substr (for a substring of a string). gawk provides functionsfor timestamp management, bit manipulation, and runtime string translation.(See Section 8.1 [Built-in Functions], page 130.)Built-in VariableARGC, ARGV, CONVFMT, ENVIRON, FILENAME, FNR, FS, NF, NR, OFMT, OFS, ORS,RLENGTH, RSTART, RS, and SUBSEP are the variables that have special meaningto awk. In addition, ARGIND, BINMODE, ERRNO, FIELDWIDTHS, IGNORECASE, LINT,PROCINFO, RT, and TEXTDOMAIN are the variables that have special meaningto gawk. Changing some of them affects awk’s running environment. (SeeSection 6.5 [Built-in Variables], page 110.)BracesSee “Curly Braces.”Bulletin Board SystemA computer system allowing users to log in and read and/or leave messages forother users of the system, much like leaving paper notes on a bulletin board.CThe system programming language that most GNU software is written in. Theawk programming language has C-like syntax, and this book points out similaritiesbetween awk and C when appropriate.In general, gawk attempts to be as similar to the 1990 version of ISO C asmakes sense. Future versions of gawk may adopt features from the newer 1999standard, as appropriate.C++ A popular object-oriented programming language derived from C.