| 1 | .\" Automatically generated by Pod::Man v1.34, Pod::Parser v1.13 |
| 2 | .\" |
| 3 | .\" Standard preamble: |
| 4 | .\" ======================================================================== |
| 5 | .de Sh \" Subsection heading |
| 6 | .br |
| 7 | .if t .Sp |
| 8 | .ne 5 |
| 9 | .PP |
| 10 | \fB\\$1\fR |
| 11 | .PP |
| 12 | .. |
| 13 | .de Sp \" Vertical space (when we can't use .PP) |
| 14 | .if t .sp .5v |
| 15 | .if n .sp |
| 16 | .. |
| 17 | .de Vb \" Begin verbatim text |
| 18 | .ft CW |
| 19 | .nf |
| 20 | .ne \\$1 |
| 21 | .. |
| 22 | .de Ve \" End verbatim text |
| 23 | .ft R |
| 24 | .fi |
| 25 | .. |
| 26 | .\" Set up some character translations and predefined strings. \*(-- will |
| 27 | .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left |
| 28 | .\" double quote, and \*(R" will give a right double quote. | will give a |
| 29 | .\" real vertical bar. \*(C+ will give a nicer C++. Capital omega is used to |
| 30 | .\" do unbreakable dashes and therefore won't be available. \*(C` and \*(C' |
| 31 | .\" expand to `' in nroff, nothing in troff, for use with C<>. |
| 32 | .tr \(*W-|\(bv\*(Tr |
| 33 | .ds C+ C\v'-.1v'\h'-1p'\s-2+\h'-1p'+\s0\v'.1v'\h'-1p' |
| 34 | .ie n \{\ |
| 35 | . ds -- \(*W- |
| 36 | . ds PI pi |
| 37 | . if (\n(.H=4u)&(1m=24u) .ds -- \(*W\h'-12u'\(*W\h'-12u'-\" diablo 10 pitch |
| 38 | . if (\n(.H=4u)&(1m=20u) .ds -- \(*W\h'-12u'\(*W\h'-8u'-\" diablo 12 pitch |
| 39 | . ds L" "" |
| 40 | . ds R" "" |
| 41 | . ds C` "" |
| 42 | . ds C' "" |
| 43 | 'br\} |
| 44 | .el\{\ |
| 45 | . ds -- \|\(em\| |
| 46 | . ds PI \(*p |
| 47 | . ds L" `` |
| 48 | . ds R" '' |
| 49 | 'br\} |
| 50 | .\" |
| 51 | .\" If the F register is turned on, we'll generate index entries on stderr for |
| 52 | .\" titles (.TH), headers (.SH), subsections (.Sh), items (.Ip), and index |
| 53 | .\" entries marked with X<> in POD. Of course, you'll have to process the |
| 54 | .\" output yourself in some meaningful fashion. |
| 55 | .if \nF \{\ |
| 56 | . de IX |
| 57 | . tm Index:\\$1\t\\n%\t"\\$2" |
| 58 | .. |
| 59 | . nr % 0 |
| 60 | . rr F |
| 61 | .\} |
| 62 | .\" |
| 63 | .\" For nroff, turn off justification. Always turn off hyphenation; it makes |
| 64 | .\" way too many mistakes in technical documents. |
| 65 | .hy 0 |
| 66 | .if n .na |
| 67 | .\" |
| 68 | .\" Accent mark definitions (@(#)ms.acc 1.5 88/02/08 SMI; from UCB 4.2). |
| 69 | .\" Fear. Run. Save yourself. No user-serviceable parts. |
| 70 | . \" fudge factors for nroff and troff |
| 71 | .if n \{\ |
| 72 | . ds #H 0 |
| 73 | . ds #V .8m |
| 74 | . ds #F .3m |
| 75 | . ds #[ \f1 |
| 76 | . ds #] \fP |
| 77 | .\} |
| 78 | .if t \{\ |
| 79 | . ds #H ((1u-(\\\\n(.fu%2u))*.13m) |
| 80 | . ds #V .6m |
| 81 | . ds #F 0 |
| 82 | . ds #[ \& |
| 83 | . ds #] \& |
| 84 | .\} |
| 85 | . \" simple accents for nroff and troff |
| 86 | .if n \{\ |
| 87 | . ds ' \& |
| 88 | . ds ` \& |
| 89 | . ds ^ \& |
| 90 | . ds , \& |
| 91 | . ds ~ ~ |
| 92 | . ds / |
| 93 | .\} |
| 94 | .if t \{\ |
| 95 | . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" |
| 96 | . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' |
| 97 | . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' |
| 98 | . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' |
| 99 | . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' |
| 100 | . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' |
| 101 | .\} |
| 102 | . \" troff and (daisy-wheel) nroff accents |
| 103 | .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' |
| 104 | .ds 8 \h'\*(#H'\(*b\h'-\*(#H' |
| 105 | .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] |
| 106 | .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' |
| 107 | .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' |
| 108 | .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] |
| 109 | .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] |
| 110 | .ds ae a\h'-(\w'a'u*4/10)'e |
| 111 | .ds Ae A\h'-(\w'A'u*4/10)'E |
| 112 | . \" corrections for vroff |
| 113 | .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' |
| 114 | .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' |
| 115 | . \" for low resolution devices (crt and lpr) |
| 116 | .if \n(.H>23 .if \n(.V>19 \ |
| 117 | \{\ |
| 118 | . ds : e |
| 119 | . ds 8 ss |
| 120 | . ds o a |
| 121 | . ds d- d\h'-1'\(ga |
| 122 | . ds D- D\h'-1'\(hy |
| 123 | . ds th \o'bp' |
| 124 | . ds Th \o'LP' |
| 125 | . ds ae ae |
| 126 | . ds Ae AE |
| 127 | .\} |
| 128 | .rm #[ #] #H #V #F C |
| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "A2P 1" |
| 132 | .TH A2P 1 "2002-06-01" "perl v5.8.0" "Perl Programmers Reference Guide" |
| 133 | .SH "NAME" |
| 134 | a2p \- Awk to Perl translator |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | \&\fBa2p [options] filename\fR |
| 138 | .SH "DESCRIPTION" |
| 139 | .IX Header "DESCRIPTION" |
| 140 | \&\fIA2p\fR takes an awk script specified on the command line (or from |
| 141 | standard input) and produces a comparable \fIperl\fR script on the |
| 142 | standard output. |
| 143 | .Sh "Options" |
| 144 | .IX Subsection "Options" |
| 145 | Options include: |
| 146 | .IP "\fB\-D<number>\fR" 5 |
| 147 | .IX Item "-D<number>" |
| 148 | sets debugging flags. |
| 149 | .IP "\fB\-F<character>\fR" 5 |
| 150 | .IX Item "-F<character>" |
| 151 | tells a2p that this awk script is always invoked with this \fB\-F\fR |
| 152 | switch. |
| 153 | .IP "\fB\-n<fieldlist>\fR" 5 |
| 154 | .IX Item "-n<fieldlist>" |
| 155 | specifies the names of the input fields if input does not have to be |
| 156 | split into an array. If you were translating an awk script that |
| 157 | processes the password file, you might say: |
| 158 | .Sp |
| 159 | .Vb 1 |
| 160 | \& a2p -7 -nlogin.password.uid.gid.gcos.shell.home |
| 161 | .Ve |
| 162 | .Sp |
| 163 | Any delimiter can be used to separate the field names. |
| 164 | .IP "\fB\-<number>\fR" 5 |
| 165 | .IX Item "-<number>" |
| 166 | causes a2p to assume that input will always have that many fields. |
| 167 | .IP "\fB\-o\fR" 5 |
| 168 | .IX Item "-o" |
| 169 | tells a2p to use old awk behavior. The only current differences are: |
| 170 | .RS 5 |
| 171 | .IP "\(bu" 5 |
| 172 | Old awk always has a line loop, even if there are no line |
| 173 | actions, whereas new awk does not. |
| 174 | .IP "\(bu" 5 |
| 175 | In old awk, sprintf is extremely greedy about its arguments. |
| 176 | For example, given the statement |
| 177 | .Sp |
| 178 | .Vb 1 |
| 179 | \& print sprintf(some_args), extra_args; |
| 180 | .Ve |
| 181 | .Sp |
| 182 | old awk considers \fIextra_args\fR to be arguments to \f(CW\*(C`sprintf\*(C'\fR; new awk |
| 183 | considers them arguments to \f(CW\*(C`print\*(C'\fR. |
| 184 | .RE |
| 185 | .RS 5 |
| 186 | .RE |
| 187 | .ie n .Sh """Considerations""" |
| 188 | .el .Sh "``Considerations''" |
| 189 | .IX Subsection "Considerations" |
| 190 | A2p cannot do as good a job translating as a human would, but it |
| 191 | usually does pretty well. There are some areas where you may want to |
| 192 | examine the perl script produced and tweak it some. Here are some of |
| 193 | them, in no particular order. |
| 194 | .PP |
| 195 | There is an awk idiom of putting \fIint()\fR around a string expression to |
| 196 | force numeric interpretation, even though the argument is always |
| 197 | integer anyway. This is generally unneeded in perl, but a2p can't |
| 198 | tell if the argument is always going to be integer, so it leaves it |
| 199 | in. You may wish to remove it. |
| 200 | .PP |
| 201 | Perl differentiates numeric comparison from string comparison. Awk |
| 202 | has one operator for both that decides at run time which comparison to |
| 203 | do. A2p does not try to do a complete job of awk emulation at this |
| 204 | point. Instead it guesses which one you want. It's almost always |
| 205 | right, but it can be spoofed. All such guesses are marked with the |
| 206 | comment "\f(CW\*(C`#???\*(C'\fR". You should go through and check them. You might |
| 207 | want to run at least once with the \fB\-w\fR switch to perl, which will |
| 208 | warn you if you use == where you should have used eq. |
| 209 | .PP |
| 210 | Perl does not attempt to emulate the behavior of awk in which |
| 211 | nonexistent array elements spring into existence simply by being |
| 212 | referenced. If somehow you are relying on this mechanism to create |
| 213 | null entries for a subsequent for...in, they won't be there in perl. |
| 214 | .PP |
| 215 | If a2p makes a split line that assigns to a list of variables that |
| 216 | looks like (Fld1, Fld2, Fld3...) you may want to rerun a2p using the |
| 217 | \&\fB\-n\fR option mentioned above. This will let you name the fields |
| 218 | throughout the script. If it splits to an array instead, the script |
| 219 | is probably referring to the number of fields somewhere. |
| 220 | .PP |
| 221 | The exit statement in awk doesn't necessarily exit; it goes to the \s-1END\s0 |
| 222 | block if there is one. Awk scripts that do contortions within the \s-1END\s0 |
| 223 | block to bypass the block under such circumstances can be simplified |
| 224 | by removing the conditional in the \s-1END\s0 block and just exiting directly |
| 225 | from the perl script. |
| 226 | .PP |
| 227 | Perl has two kinds of array, numerically-indexed and associative. |
| 228 | Perl associative arrays are called \*(L"hashes\*(R". Awk arrays are usually |
| 229 | translated to hashes, but if you happen to know that the index is |
| 230 | always going to be numeric you could change the {...} to [...]. |
| 231 | Iteration over a hash is done using the \fIkeys()\fR function, but iteration |
| 232 | over an array is \s-1NOT\s0. You might need to modify any loop that iterates |
| 233 | over such an array. |
| 234 | .PP |
| 235 | Awk starts by assuming \s-1OFMT\s0 has the value %.6g. Perl starts by |
| 236 | assuming its equivalent, $#, to have the value %.20g. You'll want to |
| 237 | set $# explicitly if you use the default value of \s-1OFMT\s0. |
| 238 | .PP |
| 239 | Near the top of the line loop will be the split operation that is |
| 240 | implicit in the awk script. There are times when you can move this |
| 241 | down past some conditionals that test the entire record so that the |
| 242 | split is not done as often. |
| 243 | .PP |
| 244 | For aesthetic reasons you may wish to change the array base $[ from 1 |
| 245 | back to perl's default of 0, but remember to change all array |
| 246 | subscripts \s-1AND\s0 all \fIsubstr()\fR and \fIindex()\fR operations to match. |
| 247 | .PP |
| 248 | Cute comments that say \*(L"# Here is a workaround because awk is dumb\*(R" |
| 249 | are passed through unmodified. |
| 250 | .PP |
| 251 | Awk scripts are often embedded in a shell script that pipes stuff into |
| 252 | and out of awk. Often the shell script wrapper can be incorporated |
| 253 | into the perl script, since perl can start up pipes into and out of |
| 254 | itself, and can do other things that awk can't do by itself. |
| 255 | .PP |
| 256 | Scripts that refer to the special variables \s-1RSTART\s0 and \s-1RLENGTH\s0 can |
| 257 | often be simplified by referring to the variables $`, $& and $', as |
| 258 | long as they are within the scope of the pattern match that sets them. |
| 259 | .PP |
| 260 | The produced perl script may have subroutines defined to deal with |
| 261 | awk's semantics regarding getline and print. Since a2p usually picks |
| 262 | correctness over efficiency. it is almost always possible to rewrite |
| 263 | such code to be more efficient by discarding the semantic sugar. |
| 264 | .PP |
| 265 | For efficiency, you may wish to remove the keyword from any return |
| 266 | statement that is the last statement executed in a subroutine. A2p |
| 267 | catches the most common case, but doesn't analyze embedded blocks for |
| 268 | subtler cases. |
| 269 | .PP |
| 270 | ARGV[0] translates to \f(CW$ARGV0\fR, but ARGV[n] translates to \f(CW$ARGV\fR[$n]. A |
| 271 | loop that tries to iterate over ARGV[0] won't find it. |
| 272 | .SH "ENVIRONMENT" |
| 273 | .IX Header "ENVIRONMENT" |
| 274 | A2p uses no environment variables. |
| 275 | .SH "AUTHOR" |
| 276 | .IX Header "AUTHOR" |
| 277 | Larry Wall <\fIlarry@wall.org\fR> |
| 278 | .SH "FILES" |
| 279 | .IX Header "FILES" |
| 280 | .SH "SEE ALSO" |
| 281 | .IX Header "SEE ALSO" |
| 282 | .Vb 1 |
| 283 | \& perl The perl compiler/interpreter |
| 284 | .Ve |
| 285 | .PP |
| 286 | .Vb 1 |
| 287 | \& s2p sed to perl translator |
| 288 | .Ve |
| 289 | .SH "DIAGNOSTICS" |
| 290 | .IX Header "DIAGNOSTICS" |
| 291 | .SH "BUGS" |
| 292 | .IX Header "BUGS" |
| 293 | It would be possible to emulate awk's behavior in selecting string |
| 294 | versus numeric operations at run time by inspection of the operands, |
| 295 | but it would be gross and inefficient. Besides, a2p almost always |
| 296 | guesses right. |
| 297 | .PP |
| 298 | Storage for the awk syntax tree is currently static, and can run out. |