GAWK: Effective AWK Programming

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viGAWK: Effective AWK Programming10 Advanced Features of gawk . . . . . . . . . . . . . . . . . 16910.1 Allowing Nondecimal Input Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . 16910.2 Two-Way Communications with Another Process. . . . . . . . . . . . 17010.3 Using gawk for Network Programming. . . . . . . . . . . . . . . . . . . . . . . 17210.4 Using gawk with BSD Portals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17310.5 Profiling Your awk Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17311 Running awk and gawk . . . . . . . . . . . . . . . . . . . . . . 17711.1 Invoking awk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17711.2 Command-Line Options. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17711.3 Other Command-Line Arguments . . . . . . . . . . . . . . . . . . . . . . . . . . . 18211.4 The AWKPATH Environment Variable . . . . . . . . . . . . . . . . . . . . . . . . . 18311.5 gawk’s Exit Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18411.6 Obsolete Options and/or Features . . . . . . . . . . . . . . . . . . . . . . . . . . . 18411.7 Undocumented Options and Features. . . . . . . . . . . . . . . . . . . . . . . . 18411.8 Known Bugs in gawk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18512 A Library of awk Functions . . . . . . . . . . . . . . . . . 18612.1 Naming Library Function Global Variables . . . . . . . . . . . . . . . . . . 18612.2 General Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18812.2.1 Implementing nextfile as a Function . . . . . . . . . . . . . . . . . . 18812.2.2 Converting Strings To Numbers . . . . . . . . . . . . . . . . . . . . . . . . 18912.2.3 Assertions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19012.2.4 Rounding Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19212.2.5 The Cliff Random Number Generator . . . . . . . . . . . . . . . . . . 19312.2.6 Translating Between Characters and Numbers . . . . . . . . . . 19312.2.7 Merging an Array into a String. . . . . . . . . . . . . . . . . . . . . . . . . 19512.2.8 Managing the Time of Day . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19512.3 Data File Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19712.3.1 Noting Data File Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . 19712.3.2 Rereading the Current File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19812.3.3 Checking for Readable Data Files . . . . . . . . . . . . . . . . . . . . . . 19912.3.4 Checking For Zero-length Files . . . . . . . . . . . . . . . . . . . . . . . . . 19912.3.5 Treating Assignments as File Names. . . . . . . . . . . . . . . . . . . . 20012.4 Processing Command-Line Options . . . . . . . . . . . . . . . . . . . . . . . . . 20112.5 Reading the User Database . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20612.6 Reading the Group Database. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
13 Practical awk Programs . . . . . . . . . . . . . . . . . . . . . 21513.1 Running the Example Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21513.2 Reinventing Wheels for Fun and Profit . . . . . . . . . . . . . . . . . . . . . . 21513.2.1 Cutting out Fields and Columns . . . . . . . . . . . . . . . . . . . . . . . 21513.2.2 Searching for Regular Expressions in Files . . . . . . . . . . . . . . 22013.2.3 Printing out User Information . . . . . . . . . . . . . . . . . . . . . . . . . . 22413.2.4 Splitting a Large File into Pieces . . . . . . . . . . . . . . . . . . . . . . . 22613.2.5 Duplicating Output into Multiple Files . . . . . . . . . . . . . . . . . 22813.2.6 Printing Nonduplicated Lines of Text. . . . . . . . . . . . . . . . . . . 22913.2.7 Counting Things . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23313.3 A Grab Bag of awk Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23513.3.1 Finding Duplicated Words in a Document . . . . . . . . . . . . . . 23513.3.2 An Alarm Clock Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23613.3.3 Transliterating Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23813.3.4 Printing Mailing Labels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24013.3.5 Generating Word-Usage Counts . . . . . . . . . . . . . . . . . . . . . . . . 24213.3.6 Removing Duplicates from Unsorted Text . . . . . . . . . . . . . . 24413.3.7 Extracting Programs from Texinfo Source Files . . . . . . . . . 24513.3.8 A Simple Stream Editor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24813.3.9 An Easy Way to Use Library Functions . . . . . . . . . . . . . . . . 24913.3.10 And Now For Something Completely Different. . . . . . . . . 256viiAppendix A The Evolution of the awk Language. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257A.1 Major Changes Between V7 and SVR3.1 . . . . . . . . . . . . . . . . . . . . . 257A.2 Changes Between SVR3.1 and SVR4. . . . . . . . . . . . . . . . . . . . . . . . . 258A.3 Changes Between SVR4 and POSIX awk . . . . . . . . . . . . . . . . . . . . . 258A.4 Extensions in the Bell Laboratories awk . . . . . . . . . . . . . . . . . . . . . . 259A.5 Extensions in gawk Not in POSIX awk . . . . . . . . . . . . . . . . . . . . . . . 260A.6 Major Contributors to gawk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263Appendix B Installing gawk . . . . . . . . . . . . . . . . . . . 265B.1 The gawk Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265B.1.1 Getting the gawk Distribution. . . . . . . . . . . . . . . . . . . . . . . . . . . 265B.1.2 Extracting the Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265B.1.3 Contents of the gawk Distribution . . . . . . . . . . . . . . . . . . . . . . . 265B.2 Compiling and Installing gawk on Unix . . . . . . . . . . . . . . . . . . . . . . 268B.2.1 Compiling gawk for Unix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268B.2.2 Additional Configuration Options . . . . . . . . . . . . . . . . . . . . . . . 269B.2.3 The Configuration Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269B.3 Installation on Other Operating Systems . . . . . . . . . . . . . . . . . . . . . 270B.3.1 Installation on PC Operating Systems . . . . . . . . . . . . . . . . . . 270B.3.1.1 Installing a Prepared Distribution for PC Systems . . 270B.3.1.2 Compiling gawk for PC Operating Systems . . . . . . . . . 271B.3.1.3 Compiling gawk For Dynamic Libraries. . . . . . . . . . . . . 272B.3.1.4 Using gawk on PC Operating Systems . . . . . . . . . . . . . . 273B.3.1.5 Using gawk In The Cygwin Environment . . . . . . . . . . . 275
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