GAWK: Effective AWK Programming

More documents

Recommendations

Info

204 GAWK: Effective AWK Programmingif (_opti == 0)_opti = 2thisopt = substr(argv[Optind], _opti, 1)Optopt = thisopti = index(options, thisopt)if (i == 0) {if (Opterr)printf("%c -- invalid option\n",thisopt) > "/dev/stderr"if (_opti >= length(argv[Optind])) {Optind++_opti = 0} else_opti++return "?"}The _opti variable tracks the position in the current command-line argument(argv[Optind]). If multiple options are grouped together with one ‘-’ (e.g., ‘-abx’), it isnecessary to return them to the user one at a time.If _opti is equal to zero, it is set to two, which is the index in the string of the nextcharacter to look at (we skip the ‘-’, which is at position one). The variable thisopt holdsthe character, obtained with substr. It is saved in Optopt for the main program to use.If thisopt is not in the options string, then it is an invalid option. If Opterr is nonzero,getopt prints an error message on the standard error that is similar to the message fromthe C version of getopt.Because the option is invalid, it is necessary to skip it and move on to the next optioncharacter. If _opti is greater than or equal to the length of the current command-lineargument, it is necessary to move on to the next argument, so Optind is incremented and_opti is reset to zero. Otherwise, Optind is left alone and _opti is merely incremented.In any case, because the option is invalid, getopt returns ‘?’. The main program canexamine Optopt if it needs to know what the invalid option letter actually is. Continuingon:if (substr(options, i + 1, 1) == ":") {# get option argumentif (length(substr(argv[Optind], _opti + 1)) > 0)Optarg = substr(argv[Optind], _opti + 1)elseOptarg = argv[++Optind]_opti = 0} elseOptarg = ""If the option requires an argument, the option letter is followed by a colon in theoptions string. If there are remaining characters in the current command-line argument(argv[Optind]), then the rest of that string is assigned to Optarg. Otherwise, the nextcommand-line argument is used (‘-xFOO’ versus ‘-x FOO’). In either case, _opti is reset
Chapter 12: A Library of awk Functions 205to zero, because there are no more characters left to examine in the current command-lineargument. Continuing:}if (_opti == 0 || _opti >= length(argv[Optind])) {Optind++_opti = 0} else_opti++return thisoptFinally, if _opti is either zero or greater than the length of the current commandlineargument, it means this element in argv is through being processed, so Optind isincremented to point to the next element in argv. If neither condition is true, then only_opti is incremented, so that the next option letter can be processed on the next call togetopt.The BEGIN rule initializes both Opterr and Optind to one. Opterr is set to one, sincethe default behavior is for getopt to print a diagnostic message upon seeing an invalidoption. Optind is set to one, since there’s no reason to look at the program name, which isin ARGV[0]:BEGIN {Opterr = 1Optind = 1}# default is to diagnose# skip ARGV[0]# test programif (_getopt_test) {while ((_go_c = getopt(ARGC, ARGV, "ab:cd")) != -1)printf("c = , optarg = \n",_go_c, Optarg)printf("non-option arguments:\n")for (; Optind < ARGC; Optind++)printf("\tARGV[%d] = \n",Optind, ARGV[Optind])}The rest of the BEGIN rule is a simple test program. Here is the result of two sampleruns of the test program:$ awk -f getopt.awk -v _getopt_test=1 -- -a -cbARG bax -x⊣ c = , optarg = ⊣ c = , optarg = ⊣ c = , optarg = ⊣ non-option arguments:⊣ ARGV[3] = ⊣ ARGV[4] = $ awk -f getopt.awk -v _getopt_test=1 -- -a -x -- xyz abc⊣ c = , optarg =
Page 1 and 2:
GAWK: Effective AWK ProgrammingA Us
Page 3:
To Miriam, for making me complete.T
Page 6 and 7:
iiGAWK: Effective AWK ProgrammingTa
Page 8 and 9:
ivGAWK: Effective AWK Programming5
Page 10 and 11:
viGAWK: Effective AWK Programming10
Page 12 and 13:
viiiGAWK: Effective AWK Programming
Page 14 and 15:
2 GAWK: Effective AWK Programmingea
Page 16 and 17:
4 GAWK: Effective AWK ProgrammingAf
Page 18 and 19:
6 GAWK: Effective AWK ProgrammingCh
Page 20 and 21:
8 GAWK: Effective AWK ProgrammingGN
Page 22 and 23:
10 GAWK: Effective AWK Programmingt
Page 24 and 25:
12 GAWK: Effective AWK ProgrammingT
Page 26 and 27:
14 GAWK: Effective AWK Programmingp
Page 28 and 29:
16 GAWK: Effective AWK Programming$
Page 30 and 31:
Page 32 and 33:
20 GAWK: Effective AWK Programming
Page 34 and 35:
22 GAWK: Effective AWK ProgrammingH
Page 36 and 37:
24 GAWK: Effective AWK Programming2
Page 38 and 39:
26 GAWK: Effective AWK Programming\
Page 40 and 41:
28 GAWK: Effective AWK Programming[
Page 42 and 43:
30 GAWK: Effective AWK Programmings
Page 44 and 45:
Page 46 and 47:
Page 48 and 49:
Page 50 and 51:
Page 52 and 53:
40 GAWK: Effective AWK Programming$
Page 54 and 55:
42 GAWK: Effective AWK Programmingh
Page 56 and 57:
Page 58 and 59:
46 GAWK: Effective AWK ProgrammingB
Page 60 and 61:
Page 62 and 63:
Page 64 and 65:
Page 66 and 67:
54 GAWK: Effective AWK Programming{
Page 68 and 69:
Page 70 and 71:
Page 72 and 73:
Page 74 and 75:
62 GAWK: Effective AWK Programming%
Page 76 and 77:
Page 78 and 79:
66 GAWK: Effective AWK ProgrammingI
Page 80 and 81:
Page 82 and 83:
Page 84 and 85:
72 GAWK: Effective AWK ProgrammingS
Page 86 and 87:
74 GAWK: Effective AWK Programmingo
Page 88 and 89:
Page 90 and 91:
78 GAWK: Effective AWK Programmingh
Page 92 and 93:
80 GAWK: Effective AWK Programmingf
Page 94 and 95:
82 GAWK: Effective AWK Programmingx
Page 96 and 97:
Page 98 and 99:
86 GAWK: Effective AWK ProgrammingA
Page 100 and 101:
88 GAWK: Effective AWK ProgrammingU
Page 102 and 103:
90 GAWK: Effective AWK ProgrammingI
Page 104 and 105:
92 GAWK: Effective AWK ProgrammingS
Page 106 and 107:
94 GAWK: Effective AWK ProgrammingA
Page 108 and 109:
Page 110 and 111:
Page 112 and 113:
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
Page 132 and 133:
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167: 154 GAWK: Effective AWK Programming
Page 266 and 267:
Page 268 and 269:
Page 270 and 271:
Page 272 and 273:
Page 274 and 275:
Page 276 and 277:
Page 278 and 279:
Page 280 and 281:
Page 282 and 283:
Page 284 and 285:
Page 286 and 287:
Page 288 and 289:
Page 290 and 291:
Page 292 and 293:
Page 294 and 295:
Page 296 and 297:
Page 298 and 299:
Page 300 and 301:
Page 302 and 303:
Page 304 and 305:
Page 306 and 307:
Page 308 and 309:
Page 310 and 311:
Page 312 and 313:
Page 314 and 315:
Page 316 and 317:
Page 318 and 319:
Page 320 and 321:
Page 322 and 323:
Page 324 and 325:
Page 326 and 327:
Page 328 and 329:
Page 330 and 331:
Page 332 and 333:
Page 334 and 335:
Page 336 and 337:
Page 338 and 339:
Page 340 and 341:
Page 342 and 343:
Page 344 and 345:
Page 346 and 347:
Page 348 and 349:
Page 350 and 351:
Page 352 and 353:
Page 354 and 355:
Page 356 and 357:
Page 358 and 359:
Page 360 and 361:
Page 362 and 363:
Page 364:
show all

GAWK: Effective AWK Programming

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?