GAWK: Effective AWK Programming

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112 GAWK: Effective AWK ProgrammingIGNORECASE #If IGNORECASE is nonzero or non-null, then all string comparisons and all regularexpression matching are case independent. Thus, regexp matching with ‘~’ and‘!~’, as well as the gensub, gsub, index, match, split, and sub functions,record termination with RS, and field splitting with FS, all ignore case whendoing their particular regexp operations. However, the value of IGNORECASEdoes not affect array subscripting and it does not affect field splitting whenusing a single-character field separator. See Section 2.6 [Case Sensitivity inMatching], page 32.LINT #OFMTIf gawk is in compatibility mode (see Section 11.2 [Command-Line Options],page 177), then IGNORECASE has no special meaning. Thus, string and regexpoperations are always case-sensitive.When this variable is true (nonzero or non-null), gawk behaves as if the ‘--lint’command-line option is in effect. (see Section 11.2 [Command-Line Options],page 177). With a value of "fatal", lint warnings become fatal errors. Witha value of "invalid", only warnings about things that are actually invalid areissued. (This is not fully implemented yet.) Any other true value prints nonfatalwarnings. Assigning a false value to LINT turns off the lint warnings.This variable is a gawk extension. It is not special in other awk implementations.Unlike the other special variables, changing LINT does affect the production oflint warnings, even if gawk is in compatibility mode. Much as the ‘--lint’and ‘--traditional’ options independently control different aspects of gawk’sbehavior, the control of lint warnings during program execution is independentof the flavor of awk being executed.This string controls conversion of numbers to strings (see Section 5.4 [Conversionof Strings and Numbers], page 79) for printing with the print statement.It works by being passed as the first argument to the sprintf function (seeSection 8.1.3 [String-Manipulation Functions], page 132). Its default value is"%.6g". Earlier versions of awk also used OFMT to specify the format for convertingnumbers to strings in general expressions; this is now done by CONVFMT.OFS This is the output field separator (see Section 4.3 [Output Separators], page 60).It is output between the fields printed by a print statement. Its default valueis " ", a string consisting of a single space.ORSRSThis is the output record separator. It is output at the end of every printstatement. Its default value is "\n", the newline character. (See Section 4.3[Output Separators], page 60.)This is awk’s input record separator. Its default value is a string containing asingle newline character, which means that an input record consists of a singleline of text. It can also be the null string, in which case records are separatedby runs of blank lines. If it is a regexp, records are separated by matches of theregexp in the input text. (See Section 3.1 [How Input Is Split into Records],page 36.)The ability for RS to be a regular expression is a gawk extension. In most otherawk implementations, or if gawk is in compatibility mode (see Section 11.2
Chapter 6: Patterns, Actions, and Variables 113[Command-Line Options], page 177), just the first character of RS’s value isused.SUBSEP This is the subscript separator. It has the default value of "\034" and isused to separate the parts of the indices of a multidimensional array. Thus,the expression foo["A", "B"] really accesses foo["A\034B"] (see Section 7.9[Multidimensional Arrays], page 125).TEXTDOMAIN #This variable is used for internationalization of programs at the awk level. Itsets the default text domain for specially marked string constants in the sourcetext, as well as for the dcgettext, dcngettext and bindtextdomain functions(see Chapter 9 [Internationalization with gawk], page 160). The default valueof TEXTDOMAIN is "messages".This variable is a gawk extension. In other awk implementations, or if gawk isin compatibility mode (see Section 11.2 [Command-Line Options], page 177),it is not special.6.5.2 Built-in Variables That Convey InformationThe following is an alphabetical list of variables that awk sets automatically on certainoccasions in order to provide information to your program. The variables that are specificto gawk are marked with a pound sign (‘#’).ARGC, ARGVARGIND #The command-line arguments available to awk programs are stored in an arraycalled ARGV. ARGC is the number of command-line arguments present. SeeSection 11.3 [Other Command-Line Arguments], page 182. Unlike most awkarrays, ARGV is indexed from 0 to ARGC − 1. In the following example:$ awk ’BEGIN {> for (i = 0; i < ARGC; i++)> print ARGV[i]> }’ inventory-shipped BBS-list⊣ awk⊣ inventory-shipped⊣ BBS-listARGV[0] contains "awk", ARGV[1] contains "inventory-shipped", andARGV[2] contains "BBS-list". The value of ARGC is three, one more than theindex of the last element in ARGV, because the elements are numbered fromzero.The names ARGC and ARGV, as well as the convention of indexing the arrayfrom 0 to ARGC − 1, are derived from the C language’s method of accessingcommand-line arguments.The value of ARGV[0] can vary from system to system. Also, you should notethat the program text is not included in ARGV, nor are any of awk’s commandlineoptions. See Section 6.5.3 [Using ARGC and ARGV], page 116, for informationabout how awk uses these variables.The index in ARGV of the current file being processed. Every time gawk opensa new data file for processing, it sets ARGIND to the index in ARGV of the file
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