GAWK: Effective AWK Programming

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232 GAWK: Effective AWK Programming}if (charcount) {clast = substr(clast, charcount + 1)cline = substr(cline, charcount + 1)}return (clast == cline)The following two rules are the body of the program. The first one is executed only forthe very first line of data. It sets last equal to $0, so that subsequent lines of text havesomething to be compared to.The second rule does the work. The variable equal is one or zero, depending upon theresults of are_equal’s comparison. If uniq is counting repeated lines, and the lines areequal, then it increments the count variable. Otherwise, it prints the line and resets count,since the two lines are not equal.If uniq is not counting, and if the lines are equal, count is incremented. Nothing isprinted, since the point is to remove duplicates. Otherwise, if uniq is counting repeatedlines and more than one line is seen, or if uniq is counting nonrepeated lines and only oneline is seen, then the line is printed, and count is reset.Finally, similar logic is used in the END rule to print the final line of input data:NR == 1 {last = $0next}{equal = are_equal()if (do_count) { # overrides -d and -uif (equal)count++else {printf("%4d %s\n", count, last) > outputfile}}nextlast = $0count = 1# resetif (equal)count++else {if ((repeated_only && count > 1) ||(non_repeated_only && count == 1))print last > outputfilelast = $0count = 1
Chapter 13: Practical awk Programs 233}}END {if (do_count)printf("%4d %s\n", count, last) > outputfileelse if ((repeated_only && count > 1) ||(non_repeated_only && count == 1))print last > outputfile}13.2.7 Counting ThingsThe wc (word count) utility counts lines, words, and characters in one or more input files.Its usage is as follows:wc [-lwc] [ files ... ]If no files are specified on the command line, wc reads its standard input. If there aremultiple files, it also prints total counts for all the files. The options and their meaningsare shown in the following list:-l Count only lines.-w Count only words. A “word” is a contiguous sequence of nonwhitespace characters,separated by spaces and/or TABs. Luckily, this is the normal way awkseparates fields in its input data.-c Count only characters.Implementing wc in awk is particularly elegant, since awk does a lot of the work for us;it splits lines into words (i.e., fields) and counts them, it counts lines (i.e., records), and itcan easily tell us how long a line is.This uses the getopt library function (see Section 12.4 [Processing Command-Line Options],page 201) and the file-transition functions (see Section 12.3.1 [Noting Data FileBoundaries], page 197).This version has one notable difference from traditional versions of wc: it always printsthe counts in the order lines, words, and characters. Traditional versions note the order ofthe ‘-l’, ‘-w’, and ‘-c’ options on the command line, and print the counts in that order.The BEGIN rule does the argument processing. The variable print_total is true if morethan one file is named on the command line:# wc.awk --- count lines, words, characters# Options:# -l only count lines# -w only count words# -c only count characters## Default is to count lines, words, characters## Requires getopt and file transition library functions
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