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| 103 | .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' |
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| 117 | \{\ |
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| 127 | .\} |
| 128 | .rm #[ #] #H #V #F C |
| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "PERLRUN 1" |
| 132 | .TH PERLRUN 1 "2006-01-07" "perl v5.8.8" "Perl Programmers Reference Guide" |
| 133 | .SH "NAME" |
| 134 | perlrun \- how to execute the Perl interpreter |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | \&\fBperl\fR [\ \fB\-sTtuUWX\fR\ ] |
| 138 | [\ \fB\-hv\fR\ ]\ [\ \fB\-V\fR[:\fIconfigvar\fR]\ ] |
| 139 | [\ \fB\-cw\fR\ ]\ [\ \fB\-d\fR[\fBt\fR][:\fIdebugger\fR]\ ]\ [\ \fB\-D\fR[\fInumber/list\fR]\ ] |
| 140 | [\ \fB\-pna\fR\ ]\ [\ \fB\-F\fR\fIpattern\fR\ ]\ [\ \fB\-l\fR[\fIoctal\fR]\ ]\ [\ \fB\-0\fR[\fIoctal/hexadecimal\fR]\ ] |
| 141 | [\ \fB\-I\fR\fIdir\fR\ ]\ [\ \fB\-m\fR[\fB\-\fR]\fImodule\fR\ ]\ [\ \fB\-M\fR[\fB\-\fR]\fI'module...'\fR\ ]\ [\ \fB\-f\fR\ ] |
| 142 | [\ \fB\-C\ [\f(BInumber/list\fB]\ \fR] |
| 143 | [\ \fB\-P\fR\ ] |
| 144 | [\ \fB\-S\fR\ ] |
| 145 | [\ \fB\-x\fR[\fIdir\fR]\ ] |
| 146 | [\ \fB\-i\fR[\fIextension\fR]\ ] |
| 147 | [\ \fB\-e\fR\ \fI'command'\fR\ ]\ [\ \fB\-\-\fR\ ]\ [\ \fIprogramfile\fR\ ]\ [\ \fIargument\fR\ ]... |
| 148 | .SH "DESCRIPTION" |
| 149 | .IX Header "DESCRIPTION" |
| 150 | The normal way to run a Perl program is by making it directly |
| 151 | executable, or else by passing the name of the source file as an |
| 152 | argument on the command line. (An interactive Perl environment |
| 153 | is also possible\*(--see perldebug for details on how to do that.) |
| 154 | Upon startup, Perl looks for your program in one of the following |
| 155 | places: |
| 156 | .IP "1." 4 |
| 157 | Specified line by line via \fB\-e\fR switches on the command line. |
| 158 | .IP "2." 4 |
| 159 | Contained in the file specified by the first filename on the command line. |
| 160 | (Note that systems supporting the #! notation invoke interpreters this |
| 161 | way. See \*(L"Location of Perl\*(R".) |
| 162 | .IP "3." 4 |
| 163 | Passed in implicitly via standard input. This works only if there are |
| 164 | no filename arguments\*(--to pass arguments to a STDIN-read program you |
| 165 | must explicitly specify a \*(L"\-\*(R" for the program name. |
| 166 | .PP |
| 167 | With methods 2 and 3, Perl starts parsing the input file from the |
| 168 | beginning, unless you've specified a \fB\-x\fR switch, in which case it |
| 169 | scans for the first line starting with #! and containing the word |
| 170 | \&\*(L"perl\*(R", and starts there instead. This is useful for running a program |
| 171 | embedded in a larger message. (In this case you would indicate the end |
| 172 | of the program using the \f(CW\*(C`_\|_END_\|_\*(C'\fR token.) |
| 173 | .PP |
| 174 | The #! line is always examined for switches as the line is being |
| 175 | parsed. Thus, if you're on a machine that allows only one argument |
| 176 | with the #! line, or worse, doesn't even recognize the #! line, you |
| 177 | still can get consistent switch behavior regardless of how Perl was |
| 178 | invoked, even if \fB\-x\fR was used to find the beginning of the program. |
| 179 | .PP |
| 180 | Because historically some operating systems silently chopped off |
| 181 | kernel interpretation of the #! line after 32 characters, some |
| 182 | switches may be passed in on the command line, and some may not; |
| 183 | you could even get a \*(L"\-\*(R" without its letter, if you're not careful. |
| 184 | You probably want to make sure that all your switches fall either |
| 185 | before or after that 32\-character boundary. Most switches don't |
| 186 | actually care if they're processed redundantly, but getting a \*(L"\-\*(R" |
| 187 | instead of a complete switch could cause Perl to try to execute |
| 188 | standard input instead of your program. And a partial \fB\-I\fR switch |
| 189 | could also cause odd results. |
| 190 | .PP |
| 191 | Some switches do care if they are processed twice, for instance |
| 192 | combinations of \fB\-l\fR and \fB\-0\fR. Either put all the switches after |
| 193 | the 32\-character boundary (if applicable), or replace the use of |
| 194 | \&\fB\-0\fR\fIdigits\fR by \f(CW\*(C`BEGIN{ $/ = "\e0digits"; }\*(C'\fR. |
| 195 | .PP |
| 196 | Parsing of the #! switches starts wherever \*(L"perl\*(R" is mentioned in the line. |
| 197 | The sequences \*(L"\-*\*(R" and \*(L"\- \*(R" are specifically ignored so that you could, |
| 198 | if you were so inclined, say |
| 199 | .PP |
| 200 | .Vb 3 |
| 201 | \& #!/bin/sh -- # -*- perl -*- -p |
| 202 | \& eval 'exec perl -wS $0 ${1+"$@"}' |
| 203 | \& if $running_under_some_shell; |
| 204 | .Ve |
| 205 | .PP |
| 206 | to let Perl see the \fB\-p\fR switch. |
| 207 | .PP |
| 208 | A similar trick involves the \fBenv\fR program, if you have it. |
| 209 | .PP |
| 210 | .Vb 1 |
| 211 | \& #!/usr/bin/env perl |
| 212 | .Ve |
| 213 | .PP |
| 214 | The examples above use a relative path to the perl interpreter, |
| 215 | getting whatever version is first in the user's path. If you want |
| 216 | a specific version of Perl, say, perl5.005_57, you should place |
| 217 | that directly in the #! line's path. |
| 218 | .PP |
| 219 | If the #! line does not contain the word \*(L"perl\*(R", the program named after |
| 220 | the #! is executed instead of the Perl interpreter. This is slightly |
| 221 | bizarre, but it helps people on machines that don't do #!, because they |
| 222 | can tell a program that their \s-1SHELL\s0 is \fI/usr/bin/perl\fR, and Perl will then |
| 223 | dispatch the program to the correct interpreter for them. |
| 224 | .PP |
| 225 | After locating your program, Perl compiles the entire program to an |
| 226 | internal form. If there are any compilation errors, execution of the |
| 227 | program is not attempted. (This is unlike the typical shell script, |
| 228 | which might run part-way through before finding a syntax error.) |
| 229 | .PP |
| 230 | If the program is syntactically correct, it is executed. If the program |
| 231 | runs off the end without hitting an \fIexit()\fR or \fIdie()\fR operator, an implicit |
| 232 | \&\f(CWexit(0)\fR is provided to indicate successful completion. |
| 233 | .Sh "#! and quoting on non-Unix systems" |
| 234 | .IX Xref "hashbang #!" |
| 235 | .IX Subsection "#! and quoting on non-Unix systems" |
| 236 | Unix's #! technique can be simulated on other systems: |
| 237 | .IP "\s-1OS/2\s0" 4 |
| 238 | .IX Item "OS/2" |
| 239 | Put |
| 240 | .Sp |
| 241 | .Vb 1 |
| 242 | \& extproc perl -S -your_switches |
| 243 | .Ve |
| 244 | .Sp |
| 245 | as the first line in \f(CW\*(C`*.cmd\*(C'\fR file (\fB\-S\fR due to a bug in cmd.exe's |
| 246 | `extproc' handling). |
| 247 | .IP "MS-DOS" 4 |
| 248 | .IX Item "MS-DOS" |
| 249 | Create a batch file to run your program, and codify it in |
| 250 | \&\f(CW\*(C`ALTERNATE_SHEBANG\*(C'\fR (see the \fIdosish.h\fR file in the source |
| 251 | distribution for more information). |
| 252 | .IP "Win95/NT" 4 |
| 253 | .IX Item "Win95/NT" |
| 254 | The Win95/NT installation, when using the ActiveState installer for Perl, |
| 255 | will modify the Registry to associate the \fI.pl\fR extension with the perl |
| 256 | interpreter. If you install Perl by other means (including building from |
| 257 | the sources), you may have to modify the Registry yourself. Note that |
| 258 | this means you can no longer tell the difference between an executable |
| 259 | Perl program and a Perl library file. |
| 260 | .IP "Macintosh" 4 |
| 261 | .IX Item "Macintosh" |
| 262 | Under \*(L"Classic\*(R" MacOS, a perl program will have the appropriate Creator and |
| 263 | Type, so that double-clicking them will invoke the MacPerl application. |
| 264 | Under Mac \s-1OS\s0 X, clickable apps can be made from any \f(CW\*(C`#!\*(C'\fR script using Wil |
| 265 | Sanchez' DropScript utility: http://www.wsanchez.net/software/ . |
| 266 | .IP "\s-1VMS\s0" 4 |
| 267 | .IX Item "VMS" |
| 268 | Put |
| 269 | .Sp |
| 270 | .Vb 2 |
| 271 | \& $ perl -mysw 'f$env("procedure")' 'p1' 'p2' 'p3' 'p4' 'p5' 'p6' 'p7' 'p8' ! |
| 272 | \& $ exit++ + ++$status != 0 and $exit = $status = undef; |
| 273 | .Ve |
| 274 | .Sp |
| 275 | at the top of your program, where \fB\-mysw\fR are any command line switches you |
| 276 | want to pass to Perl. You can now invoke the program directly, by saying |
| 277 | \&\f(CW\*(C`perl program\*(C'\fR, or as a \s-1DCL\s0 procedure, by saying \f(CW@program\fR (or implicitly |
| 278 | via \fI\s-1DCL$PATH\s0\fR by just using the name of the program). |
| 279 | .Sp |
| 280 | This incantation is a bit much to remember, but Perl will display it for |
| 281 | you if you say \f(CW\*(C`perl "\-V:startperl"\*(C'\fR. |
| 282 | .PP |
| 283 | Command-interpreters on non-Unix systems have rather different ideas |
| 284 | on quoting than Unix shells. You'll need to learn the special |
| 285 | characters in your command-interpreter (\f(CW\*(C`*\*(C'\fR, \f(CW\*(C`\e\*(C'\fR and \f(CW\*(C`"\*(C'\fR are |
| 286 | common) and how to protect whitespace and these characters to run |
| 287 | one-liners (see \fB\-e\fR below). |
| 288 | .PP |
| 289 | On some systems, you may have to change single-quotes to double ones, |
| 290 | which you must \fInot\fR do on Unix or Plan 9 systems. You might also |
| 291 | have to change a single % to a %%. |
| 292 | .PP |
| 293 | For example: |
| 294 | .PP |
| 295 | .Vb 2 |
| 296 | \& # Unix |
| 297 | \& perl -e 'print "Hello world\en"' |
| 298 | .Ve |
| 299 | .PP |
| 300 | .Vb 2 |
| 301 | \& # MS-DOS, etc. |
| 302 | \& perl -e "print \e"Hello world\en\e"" |
| 303 | .Ve |
| 304 | .PP |
| 305 | .Vb 3 |
| 306 | \& # Macintosh |
| 307 | \& print "Hello world\en" |
| 308 | \& (then Run "Myscript" or Shift-Command-R) |
| 309 | .Ve |
| 310 | .PP |
| 311 | .Vb 2 |
| 312 | \& # VMS |
| 313 | \& perl -e "print ""Hello world\en""" |
| 314 | .Ve |
| 315 | .PP |
| 316 | The problem is that none of this is reliable: it depends on the |
| 317 | command and it is entirely possible neither works. If \fB4DOS\fR were |
| 318 | the command shell, this would probably work better: |
| 319 | .PP |
| 320 | .Vb 1 |
| 321 | \& perl -e "print <Ctrl-x>"Hello world\en<Ctrl-x>"" |
| 322 | .Ve |
| 323 | .PP |
| 324 | \&\fB\s-1CMD\s0.EXE\fR in Windows \s-1NT\s0 slipped a lot of standard Unix functionality in |
| 325 | when nobody was looking, but just try to find documentation for its |
| 326 | quoting rules. |
| 327 | .PP |
| 328 | Under the Macintosh, it depends which environment you are using. The MacPerl |
| 329 | shell, or \s-1MPW\s0, is much like Unix shells in its support for several |
| 330 | quoting variants, except that it makes free use of the Macintosh's non-ASCII |
| 331 | characters as control characters. |
| 332 | .PP |
| 333 | There is no general solution to all of this. It's just a mess. |
| 334 | .Sh "Location of Perl" |
| 335 | .IX Xref "perl, location of interpreter" |
| 336 | .IX Subsection "Location of Perl" |
| 337 | It may seem obvious to say, but Perl is useful only when users can |
| 338 | easily find it. When possible, it's good for both \fI/usr/bin/perl\fR |
| 339 | and \fI/usr/local/bin/perl\fR to be symlinks to the actual binary. If |
| 340 | that can't be done, system administrators are strongly encouraged |
| 341 | to put (symlinks to) perl and its accompanying utilities into a |
| 342 | directory typically found along a user's \s-1PATH\s0, or in some other |
| 343 | obvious and convenient place. |
| 344 | .PP |
| 345 | In this documentation, \f(CW\*(C`#!/usr/bin/perl\*(C'\fR on the first line of the program |
| 346 | will stand in for whatever method works on your system. You are |
| 347 | advised to use a specific path if you care about a specific version. |
| 348 | .PP |
| 349 | .Vb 1 |
| 350 | \& #!/usr/local/bin/perl5.00554 |
| 351 | .Ve |
| 352 | .PP |
| 353 | or if you just want to be running at least version, place a statement |
| 354 | like this at the top of your program: |
| 355 | .PP |
| 356 | .Vb 1 |
| 357 | \& use 5.005_54; |
| 358 | .Ve |
| 359 | .Sh "Command Switches" |
| 360 | .IX Xref "perl, command switches command switches" |
| 361 | .IX Subsection "Command Switches" |
| 362 | As with all standard commands, a single-character switch may be |
| 363 | clustered with the following switch, if any. |
| 364 | .PP |
| 365 | .Vb 1 |
| 366 | \& #!/usr/bin/perl -spi.orig # same as -s -p -i.orig |
| 367 | .Ve |
| 368 | .PP |
| 369 | Switches include: |
| 370 | .IP "\fB\-0\fR[\fIoctal/hexadecimal\fR]" 5 |
| 371 | .IX Xref "-0 $" |
| 372 | .IX Item "-0[octal/hexadecimal]" |
| 373 | specifies the input record separator (\f(CW$/\fR) as an octal or |
| 374 | hexadecimal number. If there are no digits, the null character is the |
| 375 | separator. Other switches may precede or follow the digits. For |
| 376 | example, if you have a version of \fBfind\fR which can print filenames |
| 377 | terminated by the null character, you can say this: |
| 378 | .Sp |
| 379 | .Vb 1 |
| 380 | \& find . -name '*.orig' -print0 | perl -n0e unlink |
| 381 | .Ve |
| 382 | .Sp |
| 383 | The special value 00 will cause Perl to slurp files in paragraph mode. |
| 384 | The value 0777 will cause Perl to slurp files whole because there is no |
| 385 | legal byte with that value. |
| 386 | .Sp |
| 387 | If you want to specify any Unicode character, use the hexadecimal |
| 388 | format: \f(CW\*(C`\-0xHHH...\*(C'\fR, where the \f(CW\*(C`H\*(C'\fR are valid hexadecimal digits. |
| 389 | (This means that you cannot use the \f(CW\*(C`\-x\*(C'\fR with a directory name that |
| 390 | consists of hexadecimal digits.) |
| 391 | .IP "\fB\-a\fR" 5 |
| 392 | .IX Xref "-a autosplit" |
| 393 | .IX Item "-a" |
| 394 | turns on autosplit mode when used with a \fB\-n\fR or \fB\-p\fR. An implicit |
| 395 | split command to the \f(CW@F\fR array is done as the first thing inside the |
| 396 | implicit while loop produced by the \fB\-n\fR or \fB\-p\fR. |
| 397 | .Sp |
| 398 | .Vb 1 |
| 399 | \& perl -ane 'print pop(@F), "\en";' |
| 400 | .Ve |
| 401 | .Sp |
| 402 | is equivalent to |
| 403 | .Sp |
| 404 | .Vb 4 |
| 405 | \& while (<>) { |
| 406 | \& @F = split(' '); |
| 407 | \& print pop(@F), "\en"; |
| 408 | \& } |
| 409 | .Ve |
| 410 | .Sp |
| 411 | An alternate delimiter may be specified using \fB\-F\fR. |
| 412 | .IP "\fB\-C [\f(BInumber/list\fB]\fR" 5 |
| 413 | .IX Xref "-C" |
| 414 | .IX Item "-C [number/list]" |
| 415 | The \f(CW\*(C`\-C\*(C'\fR flag controls some Unicode of the Perl Unicode features. |
| 416 | .Sp |
| 417 | As of 5.8.1, the \f(CW\*(C`\-C\*(C'\fR can be followed either by a number or a list |
| 418 | of option letters. The letters, their numeric values, and effects |
| 419 | are as follows; listing the letters is equal to summing the numbers. |
| 420 | .Sp |
| 421 | .Vb 13 |
| 422 | \& I 1 STDIN is assumed to be in UTF-8 |
| 423 | \& O 2 STDOUT will be in UTF-8 |
| 424 | \& E 4 STDERR will be in UTF-8 |
| 425 | \& S 7 I + O + E |
| 426 | \& i 8 UTF-8 is the default PerlIO layer for input streams |
| 427 | \& o 16 UTF-8 is the default PerlIO layer for output streams |
| 428 | \& D 24 i + o |
| 429 | \& A 32 the @ARGV elements are expected to be strings encoded in UTF-8 |
| 430 | \& L 64 normally the "IOEioA" are unconditional, |
| 431 | \& the L makes them conditional on the locale environment |
| 432 | \& variables (the LC_ALL, LC_TYPE, and LANG, in the order |
| 433 | \& of decreasing precedence) -- if the variables indicate |
| 434 | \& UTF-8, then the selected "IOEioA" are in effect |
| 435 | .Ve |
| 436 | .Sp |
| 437 | For example, \f(CW\*(C`\-COE\*(C'\fR and \f(CW\*(C`\-C6\*(C'\fR will both turn on UTF\-8\-ness on both |
| 438 | \&\s-1STDOUT\s0 and \s-1STDERR\s0. Repeating letters is just redundant, not cumulative |
| 439 | nor toggling. |
| 440 | .Sp |
| 441 | The \f(CW\*(C`io\*(C'\fR options mean that any subsequent \fIopen()\fR (or similar I/O |
| 442 | operations) will have the \f(CW\*(C`:utf8\*(C'\fR PerlIO layer implicitly applied |
| 443 | to them, in other words, \s-1UTF\-8\s0 is expected from any input stream, |
| 444 | and \s-1UTF\-8\s0 is produced to any output stream. This is just the default, |
| 445 | with explicit layers in \fIopen()\fR and with \fIbinmode()\fR one can manipulate |
| 446 | streams as usual. |
| 447 | .Sp |
| 448 | \&\f(CW\*(C`\-C\*(C'\fR on its own (not followed by any number or option list), or the |
| 449 | empty string \f(CW""\fR for the \f(CW\*(C`PERL_UNICODE\*(C'\fR environment variable, has the |
| 450 | same effect as \f(CW\*(C`\-CSDL\*(C'\fR. In other words, the standard I/O handles and |
| 451 | the default \f(CW\*(C`open()\*(C'\fR layer are UTF\-8\-fied \fBbut\fR only if the locale |
| 452 | environment variables indicate a \s-1UTF\-8\s0 locale. This behaviour follows |
| 453 | the \fIimplicit\fR (and problematic) \s-1UTF\-8\s0 behaviour of Perl 5.8.0. |
| 454 | .Sp |
| 455 | You can use \f(CW\*(C`\-C0\*(C'\fR (or \f(CW"0"\fR for \f(CW\*(C`PERL_UNICODE\*(C'\fR) to explicitly |
| 456 | disable all the above Unicode features. |
| 457 | .Sp |
| 458 | The read-only magic variable \f(CW\*(C`${^UNICODE}\*(C'\fR reflects the numeric value |
| 459 | of this setting. This is variable is set during Perl startup and is |
| 460 | thereafter read\-only. If you want runtime effects, use the three-arg |
| 461 | \&\fIopen()\fR (see \*(L"open\*(R" in perlfunc), the two-arg \fIbinmode()\fR (see \*(L"binmode\*(R" in perlfunc), |
| 462 | and the \f(CW\*(C`open\*(C'\fR pragma (see open). |
| 463 | .Sp |
| 464 | (In Perls earlier than 5.8.1 the \f(CW\*(C`\-C\*(C'\fR switch was a Win32\-only switch |
| 465 | that enabled the use of Unicode-aware \*(L"wide system call\*(R" Win32 APIs. |
| 466 | This feature was practically unused, however, and the command line |
| 467 | switch was therefore \*(L"recycled\*(R".) |
| 468 | .IP "\fB\-c\fR" 5 |
| 469 | .IX Xref "-c" |
| 470 | .IX Item "-c" |
| 471 | causes Perl to check the syntax of the program and then exit without |
| 472 | executing it. Actually, it \fIwill\fR execute \f(CW\*(C`BEGIN\*(C'\fR, \f(CW\*(C`CHECK\*(C'\fR, and |
| 473 | \&\f(CW\*(C`use\*(C'\fR blocks, because these are considered as occurring outside the |
| 474 | execution of your program. \f(CW\*(C`INIT\*(C'\fR and \f(CW\*(C`END\*(C'\fR blocks, however, will |
| 475 | be skipped. |
| 476 | .IP "\fB\-d\fR" 5 |
| 477 | .IX Xref "-d -dt" |
| 478 | .IX Item "-d" |
| 479 | .PD 0 |
| 480 | .IP "\fB\-dt\fR" 5 |
| 481 | .IX Item "-dt" |
| 482 | .PD |
| 483 | runs the program under the Perl debugger. See perldebug. |
| 484 | If \fBt\fR is specified, it indicates to the debugger that threads |
| 485 | will be used in the code being debugged. |
| 486 | .IP "\fB\-d:\fR\fIfoo[=bar,baz]\fR" 5 |
| 487 | .IX Xref "-d -dt" |
| 488 | .IX Item "-d:foo[=bar,baz]" |
| 489 | .PD 0 |
| 490 | .IP "\fB\-dt:\fR\fIfoo[=bar,baz]\fR" 5 |
| 491 | .IX Item "-dt:foo[=bar,baz]" |
| 492 | .PD |
| 493 | runs the program under the control of a debugging, profiling, or |
| 494 | tracing module installed as Devel::foo. E.g., \fB\-d:DProf\fR executes |
| 495 | the program using the Devel::DProf profiler. As with the \fB\-M\fR |
| 496 | flag, options may be passed to the Devel::foo package where they |
| 497 | will be received and interpreted by the Devel::foo::import routine. |
| 498 | The comma-separated list of options must follow a \f(CW\*(C`=\*(C'\fR character. |
| 499 | If \fBt\fR is specified, it indicates to the debugger that threads |
| 500 | will be used in the code being debugged. |
| 501 | See perldebug. |
| 502 | .IP "\fB\-D\fR\fIletters\fR" 5 |
| 503 | .IX Xref "-D DEBUGGING -DDEBUGGING" |
| 504 | .IX Item "-Dletters" |
| 505 | .PD 0 |
| 506 | .IP "\fB\-D\fR\fInumber\fR" 5 |
| 507 | .IX Item "-Dnumber" |
| 508 | .PD |
| 509 | sets debugging flags. To watch how it executes your program, use |
| 510 | \&\fB\-Dtls\fR. (This works only if debugging is compiled into your |
| 511 | Perl.) Another nice value is \fB\-Dx\fR, which lists your compiled |
| 512 | syntax tree. And \fB\-Dr\fR displays compiled regular expressions; |
| 513 | the format of the output is explained in perldebguts. |
| 514 | .Sp |
| 515 | As an alternative, specify a number instead of list of letters (e.g., |
| 516 | \&\fB\-D14\fR is equivalent to \fB\-Dtls\fR): |
| 517 | .Sp |
| 518 | .Vb 22 |
| 519 | \& 1 p Tokenizing and parsing |
| 520 | \& 2 s Stack snapshots (with v, displays all stacks) |
| 521 | \& 4 l Context (loop) stack processing |
| 522 | \& 8 t Trace execution |
| 523 | \& 16 o Method and overloading resolution |
| 524 | \& 32 c String/numeric conversions |
| 525 | \& 64 P Print profiling info, preprocessor command for -P, source file input state |
| 526 | \& 128 m Memory allocation |
| 527 | \& 256 f Format processing |
| 528 | \& 512 r Regular expression parsing and execution |
| 529 | \& 1024 x Syntax tree dump |
| 530 | \& 2048 u Tainting checks |
| 531 | \& 4096 (Obsolete, previously used for LEAKTEST) |
| 532 | \& 8192 H Hash dump -- usurps values() |
| 533 | \& 16384 X Scratchpad allocation |
| 534 | \& 32768 D Cleaning up |
| 535 | \& 65536 S Thread synchronization |
| 536 | \& 131072 T Tokenising |
| 537 | \& 262144 R Include reference counts of dumped variables (eg when using -Ds) |
| 538 | \& 524288 J Do not s,t,P-debug (Jump over) opcodes within package DB |
| 539 | \& 1048576 v Verbose: use in conjunction with other flags |
| 540 | \& 8388608 q quiet - currently only suppresses the "EXECUTING" message |
| 541 | .Ve |
| 542 | .Sp |
| 543 | All these flags require \fB\-DDEBUGGING\fR when you compile the Perl |
| 544 | executable (but see Devel::Peek, re which may change this). |
| 545 | See the \fI\s-1INSTALL\s0\fR file in the Perl source distribution |
| 546 | for how to do this. This flag is automatically set if you include \fB\-g\fR |
| 547 | option when \f(CW\*(C`Configure\*(C'\fR asks you about optimizer/debugger flags. |
| 548 | .Sp |
| 549 | If you're just trying to get a print out of each line of Perl code |
| 550 | as it executes, the way that \f(CW\*(C`sh \-x\*(C'\fR provides for shell scripts, |
| 551 | you can't use Perl's \fB\-D\fR switch. Instead do this |
| 552 | .Sp |
| 553 | .Vb 2 |
| 554 | \& # If you have "env" utility |
| 555 | \& env PERLDB_OPTS="NonStop=1 AutoTrace=1 frame=2" perl -dS program |
| 556 | .Ve |
| 557 | .Sp |
| 558 | .Vb 2 |
| 559 | \& # Bourne shell syntax |
| 560 | \& $ PERLDB_OPTS="NonStop=1 AutoTrace=1 frame=2" perl -dS program |
| 561 | .Ve |
| 562 | .Sp |
| 563 | .Vb 2 |
| 564 | \& # csh syntax |
| 565 | \& % (setenv PERLDB_OPTS "NonStop=1 AutoTrace=1 frame=2"; perl -dS program) |
| 566 | .Ve |
| 567 | .Sp |
| 568 | See perldebug for details and variations. |
| 569 | .IP "\fB\-e\fR \fIcommandline\fR" 5 |
| 570 | .IX Xref "-e" |
| 571 | .IX Item "-e commandline" |
| 572 | may be used to enter one line of program. If \fB\-e\fR is given, Perl |
| 573 | will not look for a filename in the argument list. Multiple \fB\-e\fR |
| 574 | commands may be given to build up a multi-line script. Make sure |
| 575 | to use semicolons where you would in a normal program. |
| 576 | .IP "\fB\-f\fR" 5 |
| 577 | .IX Xref "-f" |
| 578 | .IX Item "-f" |
| 579 | Disable executing \fI$Config{sitelib}/sitecustomize.pl\fR at startup. |
| 580 | .Sp |
| 581 | Perl can be built so that it by default will try to execute |
| 582 | \&\fI$Config{sitelib}/sitecustomize.pl\fR at startup. This is a hook that |
| 583 | allows the sysadmin to customize how perl behaves. It can for |
| 584 | instance be used to add entries to the \f(CW@INC\fR array to make perl find |
| 585 | modules in non-standard locations. |
| 586 | .IP "\fB\-F\fR\fIpattern\fR" 5 |
| 587 | .IX Xref "-F" |
| 588 | .IX Item "-Fpattern" |
| 589 | specifies the pattern to split on if \fB\-a\fR is also in effect. The |
| 590 | pattern may be surrounded by \f(CW\*(C`//\*(C'\fR, \f(CW""\fR, or \f(CW''\fR, otherwise it will be |
| 591 | put in single quotes. You can't use literal whitespace in the pattern. |
| 592 | .IP "\fB\-h\fR" 5 |
| 593 | .IX Xref "-h" |
| 594 | .IX Item "-h" |
| 595 | prints a summary of the options. |
| 596 | .IP "\fB\-i\fR[\fIextension\fR]" 5 |
| 597 | .IX Xref "-i in-place" |
| 598 | .IX Item "-i[extension]" |
| 599 | specifies that files processed by the \f(CW\*(C`<>\*(C'\fR construct are to be |
| 600 | edited in\-place. It does this by renaming the input file, opening the |
| 601 | output file by the original name, and selecting that output file as the |
| 602 | default for \fIprint()\fR statements. The extension, if supplied, is used to |
| 603 | modify the name of the old file to make a backup copy, following these |
| 604 | rules: |
| 605 | .Sp |
| 606 | If no extension is supplied, no backup is made and the current file is |
| 607 | overwritten. |
| 608 | .Sp |
| 609 | If the extension doesn't contain a \f(CW\*(C`*\*(C'\fR, then it is appended to the |
| 610 | end of the current filename as a suffix. If the extension does |
| 611 | contain one or more \f(CW\*(C`*\*(C'\fR characters, then each \f(CW\*(C`*\*(C'\fR is replaced |
| 612 | with the current filename. In Perl terms, you could think of this |
| 613 | as: |
| 614 | .Sp |
| 615 | .Vb 1 |
| 616 | \& ($backup = $extension) =~ s/\e*/$file_name/g; |
| 617 | .Ve |
| 618 | .Sp |
| 619 | This allows you to add a prefix to the backup file, instead of (or in |
| 620 | addition to) a suffix: |
| 621 | .Sp |
| 622 | .Vb 1 |
| 623 | \& $ perl -pi'orig_*' -e 's/bar/baz/' fileA # backup to 'orig_fileA' |
| 624 | .Ve |
| 625 | .Sp |
| 626 | Or even to place backup copies of the original files into another |
| 627 | directory (provided the directory already exists): |
| 628 | .Sp |
| 629 | .Vb 1 |
| 630 | \& $ perl -pi'old/*.orig' -e 's/bar/baz/' fileA # backup to 'old/fileA.orig' |
| 631 | .Ve |
| 632 | .Sp |
| 633 | These sets of one-liners are equivalent: |
| 634 | .Sp |
| 635 | .Vb 2 |
| 636 | \& $ perl -pi -e 's/bar/baz/' fileA # overwrite current file |
| 637 | \& $ perl -pi'*' -e 's/bar/baz/' fileA # overwrite current file |
| 638 | .Ve |
| 639 | .Sp |
| 640 | .Vb 2 |
| 641 | \& $ perl -pi'.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig' |
| 642 | \& $ perl -pi'*.orig' -e 's/bar/baz/' fileA # backup to 'fileA.orig' |
| 643 | .Ve |
| 644 | .Sp |
| 645 | From the shell, saying |
| 646 | .Sp |
| 647 | .Vb 1 |
| 648 | \& $ perl -p -i.orig -e "s/foo/bar/; ... " |
| 649 | .Ve |
| 650 | .Sp |
| 651 | is the same as using the program: |
| 652 | .Sp |
| 653 | .Vb 2 |
| 654 | \& #!/usr/bin/perl -pi.orig |
| 655 | \& s/foo/bar/; |
| 656 | .Ve |
| 657 | .Sp |
| 658 | which is equivalent to |
| 659 | .Sp |
| 660 | .Vb 21 |
| 661 | \& #!/usr/bin/perl |
| 662 | \& $extension = '.orig'; |
| 663 | \& LINE: while (<>) { |
| 664 | \& if ($ARGV ne $oldargv) { |
| 665 | \& if ($extension !~ /\e*/) { |
| 666 | \& $backup = $ARGV . $extension; |
| 667 | \& } |
| 668 | \& else { |
| 669 | \& ($backup = $extension) =~ s/\e*/$ARGV/g; |
| 670 | \& } |
| 671 | \& rename($ARGV, $backup); |
| 672 | \& open(ARGVOUT, ">$ARGV"); |
| 673 | \& select(ARGVOUT); |
| 674 | \& $oldargv = $ARGV; |
| 675 | \& } |
| 676 | \& s/foo/bar/; |
| 677 | \& } |
| 678 | \& continue { |
| 679 | \& print; # this prints to original filename |
| 680 | \& } |
| 681 | \& select(STDOUT); |
| 682 | .Ve |
| 683 | .Sp |
| 684 | except that the \fB\-i\fR form doesn't need to compare \f(CW$ARGV\fR to \f(CW$oldargv\fR to |
| 685 | know when the filename has changed. It does, however, use \s-1ARGVOUT\s0 for |
| 686 | the selected filehandle. Note that \s-1STDOUT\s0 is restored as the default |
| 687 | output filehandle after the loop. |
| 688 | .Sp |
| 689 | As shown above, Perl creates the backup file whether or not any output |
| 690 | is actually changed. So this is just a fancy way to copy files: |
| 691 | .Sp |
| 692 | .Vb 3 |
| 693 | \& $ perl -p -i'/some/file/path/*' -e 1 file1 file2 file3... |
| 694 | \&or |
| 695 | \& $ perl -p -i'.orig' -e 1 file1 file2 file3... |
| 696 | .Ve |
| 697 | .Sp |
| 698 | You can use \f(CW\*(C`eof\*(C'\fR without parentheses to locate the end of each input |
| 699 | file, in case you want to append to each file, or reset line numbering |
| 700 | (see example in \*(L"eof\*(R" in perlfunc). |
| 701 | .Sp |
| 702 | If, for a given file, Perl is unable to create the backup file as |
| 703 | specified in the extension then it will skip that file and continue on |
| 704 | with the next one (if it exists). |
| 705 | .Sp |
| 706 | For a discussion of issues surrounding file permissions and \fB\-i\fR, |
| 707 | see \*(L"Why does Perl let me delete read-only files? Why does \-i clobber protected files? Isn't this a bug in Perl?\*(R" in perlfaq5. |
| 708 | .Sp |
| 709 | You cannot use \fB\-i\fR to create directories or to strip extensions from |
| 710 | files. |
| 711 | .Sp |
| 712 | Perl does not expand \f(CW\*(C`~\*(C'\fR in filenames, which is good, since some |
| 713 | folks use it for their backup files: |
| 714 | .Sp |
| 715 | .Vb 1 |
| 716 | \& $ perl -pi~ -e 's/foo/bar/' file1 file2 file3... |
| 717 | .Ve |
| 718 | .Sp |
| 719 | Note that because \fB\-i\fR renames or deletes the original file before |
| 720 | creating a new file of the same name, UNIX-style soft and hard links will |
| 721 | not be preserved. |
| 722 | .Sp |
| 723 | Finally, the \fB\-i\fR switch does not impede execution when no |
| 724 | files are given on the command line. In this case, no backup is made |
| 725 | (the original file cannot, of course, be determined) and processing |
| 726 | proceeds from \s-1STDIN\s0 to \s-1STDOUT\s0 as might be expected. |
| 727 | .IP "\fB\-I\fR\fIdirectory\fR" 5 |
| 728 | .IX Xref "-I @INC" |
| 729 | .IX Item "-Idirectory" |
| 730 | Directories specified by \fB\-I\fR are prepended to the search path for |
| 731 | modules (\f(CW@INC\fR), and also tells the C preprocessor where to search for |
| 732 | include files. The C preprocessor is invoked with \fB\-P\fR; by default it |
| 733 | searches /usr/include and /usr/lib/perl. |
| 734 | .IP "\fB\-l\fR[\fIoctnum\fR]" 5 |
| 735 | .IX Xref "-l $ $\" |
| 736 | .IX Item "-l[octnum]" |
| 737 | enables automatic line-ending processing. It has two separate |
| 738 | effects. First, it automatically chomps \f(CW$/\fR (the input record |
| 739 | separator) when used with \fB\-n\fR or \fB\-p\fR. Second, it assigns \f(CW\*(C`$\e\*(C'\fR |
| 740 | (the output record separator) to have the value of \fIoctnum\fR so |
| 741 | that any print statements will have that separator added back on. |
| 742 | If \fIoctnum\fR is omitted, sets \f(CW\*(C`$\e\*(C'\fR to the current value of |
| 743 | \&\f(CW$/\fR. For instance, to trim lines to 80 columns: |
| 744 | .Sp |
| 745 | .Vb 1 |
| 746 | \& perl -lpe 'substr($_, 80) = ""' |
| 747 | .Ve |
| 748 | .Sp |
| 749 | Note that the assignment \f(CW\*(C`$\e = $/\*(C'\fR is done when the switch is processed, |
| 750 | so the input record separator can be different than the output record |
| 751 | separator if the \fB\-l\fR switch is followed by a \fB\-0\fR switch: |
| 752 | .Sp |
| 753 | .Vb 1 |
| 754 | \& gnufind / -print0 | perl -ln0e 'print "found $_" if -p' |
| 755 | .Ve |
| 756 | .Sp |
| 757 | This sets \f(CW\*(C`$\e\*(C'\fR to newline and then sets \f(CW$/\fR to the null character. |
| 758 | .IP "\fB\-m\fR[\fB\-\fR]\fImodule\fR" 5 |
| 759 | .IX Xref "-m -M" |
| 760 | .IX Item "-m[-]module" |
| 761 | .PD 0 |
| 762 | .IP "\fB\-M\fR[\fB\-\fR]\fImodule\fR" 5 |
| 763 | .IX Item "-M[-]module" |
| 764 | .IP "\fB\-M\fR[\fB\-\fR]\fI'module ...'\fR" 5 |
| 765 | .IX Item "-M[-]'module ...'" |
| 766 | .IP "\fB\-[mM]\fR[\fB\-\fR]\fImodule=arg[,arg]...\fR" 5 |
| 767 | .IX Item "-[mM][-]module=arg[,arg]..." |
| 768 | .PD |
| 769 | \&\fB\-m\fR\fImodule\fR executes \f(CW\*(C`use\*(C'\fR \fImodule\fR \f(CW\*(C`();\*(C'\fR before executing your |
| 770 | program. |
| 771 | .Sp |
| 772 | \&\fB\-M\fR\fImodule\fR executes \f(CW\*(C`use\*(C'\fR \fImodule\fR \f(CW\*(C`;\*(C'\fR before executing your |
| 773 | program. You can use quotes to add extra code after the module name, |
| 774 | e.g., \f(CW'\-Mmodule qw(foo bar)'\fR. |
| 775 | .Sp |
| 776 | If the first character after the \fB\-M\fR or \fB\-m\fR is a dash (\f(CW\*(C`\-\*(C'\fR) |
| 777 | then the 'use' is replaced with 'no'. |
| 778 | .Sp |
| 779 | A little builtin syntactic sugar means you can also say |
| 780 | \&\fB\-mmodule=foo,bar\fR or \fB\-Mmodule=foo,bar\fR as a shortcut for |
| 781 | \&\f(CW'\-Mmodule qw(foo bar)'\fR. This avoids the need to use quotes when |
| 782 | importing symbols. The actual code generated by \fB\-Mmodule=foo,bar\fR is |
| 783 | \&\f(CW\*(C`use module split(/,/,q{foo,bar})\*(C'\fR. Note that the \f(CW\*(C`=\*(C'\fR form |
| 784 | removes the distinction between \fB\-m\fR and \fB\-M\fR. |
| 785 | .Sp |
| 786 | A consequence of this is that \fB\-MFoo=number\fR never does a version check |
| 787 | (unless \f(CW\*(C`Foo::import()\*(C'\fR itself is set up to do a version check, which |
| 788 | could happen for example if Foo inherits from Exporter.) |
| 789 | .IP "\fB\-n\fR" 5 |
| 790 | .IX Xref "-n" |
| 791 | .IX Item "-n" |
| 792 | causes Perl to assume the following loop around your program, which |
| 793 | makes it iterate over filename arguments somewhat like \fBsed \-n\fR or |
| 794 | \&\fBawk\fR: |
| 795 | .Sp |
| 796 | .Vb 4 |
| 797 | \& LINE: |
| 798 | \& while (<>) { |
| 799 | \& ... # your program goes here |
| 800 | \& } |
| 801 | .Ve |
| 802 | .Sp |
| 803 | Note that the lines are not printed by default. See \fB\-p\fR to have |
| 804 | lines printed. If a file named by an argument cannot be opened for |
| 805 | some reason, Perl warns you about it and moves on to the next file. |
| 806 | .Sp |
| 807 | Here is an efficient way to delete all files that haven't been modified for |
| 808 | at least a week: |
| 809 | .Sp |
| 810 | .Vb 1 |
| 811 | \& find . -mtime +7 -print | perl -nle unlink |
| 812 | .Ve |
| 813 | .Sp |
| 814 | This is faster than using the \fB\-exec\fR switch of \fBfind\fR because you don't |
| 815 | have to start a process on every filename found. It does suffer from |
| 816 | the bug of mishandling newlines in pathnames, which you can fix if |
| 817 | you follow the example under \fB\-0\fR. |
| 818 | .Sp |
| 819 | \&\f(CW\*(C`BEGIN\*(C'\fR and \f(CW\*(C`END\*(C'\fR blocks may be used to capture control before or after |
| 820 | the implicit program loop, just as in \fBawk\fR. |
| 821 | .IP "\fB\-p\fR" 5 |
| 822 | .IX Xref "-p" |
| 823 | .IX Item "-p" |
| 824 | causes Perl to assume the following loop around your program, which |
| 825 | makes it iterate over filename arguments somewhat like \fBsed\fR: |
| 826 | .Sp |
| 827 | .Vb 6 |
| 828 | \& LINE: |
| 829 | \& while (<>) { |
| 830 | \& ... # your program goes here |
| 831 | \& } continue { |
| 832 | \& print or die "-p destination: $!\en"; |
| 833 | \& } |
| 834 | .Ve |
| 835 | .Sp |
| 836 | If a file named by an argument cannot be opened for some reason, Perl |
| 837 | warns you about it, and moves on to the next file. Note that the |
| 838 | lines are printed automatically. An error occurring during printing is |
| 839 | treated as fatal. To suppress printing use the \fB\-n\fR switch. A \fB\-p\fR |
| 840 | overrides a \fB\-n\fR switch. |
| 841 | .Sp |
| 842 | \&\f(CW\*(C`BEGIN\*(C'\fR and \f(CW\*(C`END\*(C'\fR blocks may be used to capture control before or after |
| 843 | the implicit loop, just as in \fBawk\fR. |
| 844 | .IP "\fB\-P\fR" 5 |
| 845 | .IX Xref "-P" |
| 846 | .IX Item "-P" |
| 847 | \&\fB\s-1NOTE:\s0 Use of \-P is strongly discouraged because of its inherent |
| 848 | problems, including poor portability.\fR |
| 849 | .Sp |
| 850 | This option causes your program to be run through the C preprocessor before |
| 851 | compilation by Perl. Because both comments and \fBcpp\fR directives begin |
| 852 | with the # character, you should avoid starting comments with any words |
| 853 | recognized by the C preprocessor such as \f(CW"if"\fR, \f(CW"else"\fR, or \f(CW"define"\fR. |
| 854 | .Sp |
| 855 | If you're considering using \f(CW\*(C`\-P\*(C'\fR, you might also want to look at the |
| 856 | Filter::cpp module from \s-1CPAN\s0. |
| 857 | .Sp |
| 858 | The problems of \-P include, but are not limited to: |
| 859 | .RS 5 |
| 860 | .IP "*" 10 |
| 861 | The \f(CW\*(C`#!\*(C'\fR line is stripped, so any switches there don't apply. |
| 862 | .IP "*" 10 |
| 863 | A \f(CW\*(C`\-P\*(C'\fR on a \f(CW\*(C`#!\*(C'\fR line doesn't work. |
| 864 | .IP "*" 10 |
| 865 | \&\fBAll\fR lines that begin with (whitespace and) a \f(CW\*(C`#\*(C'\fR but |
| 866 | do not look like cpp commands, are stripped, including anything |
| 867 | inside Perl strings, regular expressions, and here-docs . |
| 868 | .IP "*" 10 |
| 869 | In some platforms the C preprocessor knows too much: it knows about |
| 870 | the \*(C+ \-style until-end-of-line comments starting with \f(CW"//"\fR. |
| 871 | This will cause problems with common Perl constructs like |
| 872 | .Sp |
| 873 | .Vb 1 |
| 874 | \& s/foo//; |
| 875 | .Ve |
| 876 | .Sp |
| 877 | because after \-P this will became illegal code |
| 878 | .Sp |
| 879 | .Vb 1 |
| 880 | \& s/foo |
| 881 | .Ve |
| 882 | .Sp |
| 883 | The workaround is to use some other quoting separator than \f(CW"/"\fR, |
| 884 | like for example \f(CW"!"\fR: |
| 885 | .Sp |
| 886 | .Vb 1 |
| 887 | \& s!foo!!; |
| 888 | .Ve |
| 889 | .IP "*" 10 |
| 890 | It requires not only a working C preprocessor but also a working |
| 891 | \&\fIsed\fR. If not on \s-1UNIX\s0, you are probably out of luck on this. |
| 892 | .IP "*" 10 |
| 893 | Script line numbers are not preserved. |
| 894 | .IP "*" 10 |
| 895 | The \f(CW\*(C`\-x\*(C'\fR does not work with \f(CW\*(C`\-P\*(C'\fR. |
| 896 | .RE |
| 897 | .RS 5 |
| 898 | .RE |
| 899 | .IP "\fB\-s\fR" 5 |
| 900 | .IX Xref "-s" |
| 901 | .IX Item "-s" |
| 902 | enables rudimentary switch parsing for switches on the command |
| 903 | line after the program name but before any filename arguments (or before |
| 904 | an argument of \fB\-\-\fR). Any switch found there is removed from \f(CW@ARGV\fR and sets the |
| 905 | corresponding variable in the Perl program. The following program |
| 906 | prints \*(L"1\*(R" if the program is invoked with a \fB\-xyz\fR switch, and \*(L"abc\*(R" |
| 907 | if it is invoked with \fB\-xyz=abc\fR. |
| 908 | .Sp |
| 909 | .Vb 2 |
| 910 | \& #!/usr/bin/perl -s |
| 911 | \& if ($xyz) { print "$xyz\en" } |
| 912 | .Ve |
| 913 | .Sp |
| 914 | Do note that a switch like \fB\-\-help\fR creates the variable ${\-help}, which is not compliant |
| 915 | with \f(CW\*(C`strict refs\*(C'\fR. Also, when using this option on a script with |
| 916 | warnings enabled you may get a lot of spurious \*(L"used only once\*(R" warnings. |
| 917 | .IP "\fB\-S\fR" 5 |
| 918 | .IX Xref "-S" |
| 919 | .IX Item "-S" |
| 920 | makes Perl use the \s-1PATH\s0 environment variable to search for the |
| 921 | program (unless the name of the program contains directory separators). |
| 922 | .Sp |
| 923 | On some platforms, this also makes Perl append suffixes to the |
| 924 | filename while searching for it. For example, on Win32 platforms, |
| 925 | the \*(L".bat\*(R" and \*(L".cmd\*(R" suffixes are appended if a lookup for the |
| 926 | original name fails, and if the name does not already end in one |
| 927 | of those suffixes. If your Perl was compiled with \s-1DEBUGGING\s0 turned |
| 928 | on, using the \-Dp switch to Perl shows how the search progresses. |
| 929 | .Sp |
| 930 | Typically this is used to emulate #! startup on platforms that don't |
| 931 | support #!. Its also convenient when debugging a script that uses #!, |
| 932 | and is thus normally found by the shell's \f(CW$PATH\fR search mechanism. |
| 933 | .Sp |
| 934 | This example works on many platforms that have a shell compatible with |
| 935 | Bourne shell: |
| 936 | .Sp |
| 937 | .Vb 3 |
| 938 | \& #!/usr/bin/perl |
| 939 | \& eval 'exec /usr/bin/perl -wS $0 ${1+"$@"}' |
| 940 | \& if $running_under_some_shell; |
| 941 | .Ve |
| 942 | .Sp |
| 943 | The system ignores the first line and feeds the program to \fI/bin/sh\fR, |
| 944 | which proceeds to try to execute the Perl program as a shell script. |
| 945 | The shell executes the second line as a normal shell command, and thus |
| 946 | starts up the Perl interpreter. On some systems \f(CW$0\fR doesn't always |
| 947 | contain the full pathname, so the \fB\-S\fR tells Perl to search for the |
| 948 | program if necessary. After Perl locates the program, it parses the |
| 949 | lines and ignores them because the variable \f(CW$running_under_some_shell\fR |
| 950 | is never true. If the program will be interpreted by csh, you will need |
| 951 | to replace \f(CW\*(C`${1+"$@"}\*(C'\fR with \f(CW$*\fR, even though that doesn't understand |
| 952 | embedded spaces (and such) in the argument list. To start up sh rather |
| 953 | than csh, some systems may have to replace the #! line with a line |
| 954 | containing just a colon, which will be politely ignored by Perl. Other |
| 955 | systems can't control that, and need a totally devious construct that |
| 956 | will work under any of \fBcsh\fR, \fBsh\fR, or Perl, such as the following: |
| 957 | .Sp |
| 958 | .Vb 3 |
| 959 | \& eval '(exit $?0)' && eval 'exec perl -wS $0 ${1+"$@"}' |
| 960 | \& & eval 'exec /usr/bin/perl -wS $0 $argv:q' |
| 961 | \& if $running_under_some_shell; |
| 962 | .Ve |
| 963 | .Sp |
| 964 | If the filename supplied contains directory separators (i.e., is an |
| 965 | absolute or relative pathname), and if that file is not found, |
| 966 | platforms that append file extensions will do so and try to look |
| 967 | for the file with those extensions added, one by one. |
| 968 | .Sp |
| 969 | On DOS-like platforms, if the program does not contain directory |
| 970 | separators, it will first be searched for in the current directory |
| 971 | before being searched for on the \s-1PATH\s0. On Unix platforms, the |
| 972 | program will be searched for strictly on the \s-1PATH\s0. |
| 973 | .IP "\fB\-t\fR" 5 |
| 974 | .IX Xref "-t" |
| 975 | .IX Item "-t" |
| 976 | Like \fB\-T\fR, but taint checks will issue warnings rather than fatal |
| 977 | errors. These warnings can be controlled normally with \f(CW\*(C`no warnings |
| 978 | qw(taint)\*(C'\fR. |
| 979 | .Sp |
| 980 | \&\fB\s-1NOTE:\s0 this is not a substitute for \-T.\fR This is meant only to be |
| 981 | used as a temporary development aid while securing legacy code: |
| 982 | for real production code and for new secure code written from scratch |
| 983 | always use the real \fB\-T\fR. |
| 984 | .IP "\fB\-T\fR" 5 |
| 985 | .IX Xref "-T" |
| 986 | .IX Item "-T" |
| 987 | forces \*(L"taint\*(R" checks to be turned on so you can test them. Ordinarily |
| 988 | these checks are done only when running setuid or setgid. It's a |
| 989 | good idea to turn them on explicitly for programs that run on behalf |
| 990 | of someone else whom you might not necessarily trust, such as \s-1CGI\s0 |
| 991 | programs or any internet servers you might write in Perl. See |
| 992 | perlsec for details. For security reasons, this option must be |
| 993 | seen by Perl quite early; usually this means it must appear early |
| 994 | on the command line or in the #! line for systems which support |
| 995 | that construct. |
| 996 | .IP "\fB\-u\fR" 5 |
| 997 | .IX Xref "-u" |
| 998 | .IX Item "-u" |
| 999 | This obsolete switch causes Perl to dump core after compiling your |
| 1000 | program. You can then in theory take this core dump and turn it |
| 1001 | into an executable file by using the \fBundump\fR program (not supplied). |
| 1002 | This speeds startup at the expense of some disk space (which you |
| 1003 | can minimize by stripping the executable). (Still, a \*(L"hello world\*(R" |
| 1004 | executable comes out to about 200K on my machine.) If you want to |
| 1005 | execute a portion of your program before dumping, use the \fIdump()\fR |
| 1006 | operator instead. Note: availability of \fBundump\fR is platform |
| 1007 | specific and may not be available for a specific port of Perl. |
| 1008 | .Sp |
| 1009 | This switch has been superseded in favor of the new Perl code |
| 1010 | generator backends to the compiler. See B and B::Bytecode |
| 1011 | for details. |
| 1012 | .IP "\fB\-U\fR" 5 |
| 1013 | .IX Xref "-U" |
| 1014 | .IX Item "-U" |
| 1015 | allows Perl to do unsafe operations. Currently the only \*(L"unsafe\*(R" |
| 1016 | operations are attempting to unlink directories while running as |
| 1017 | superuser, and running setuid programs with fatal taint checks turned |
| 1018 | into warnings. Note that the \fB\-w\fR switch (or the \f(CW$^W\fR variable) |
| 1019 | must be used along with this option to actually \fIgenerate\fR the |
| 1020 | taint-check warnings. |
| 1021 | .IP "\fB\-v\fR" 5 |
| 1022 | .IX Xref "-v" |
| 1023 | .IX Item "-v" |
| 1024 | prints the version and patchlevel of your perl executable. |
| 1025 | .IP "\fB\-V\fR" 5 |
| 1026 | .IX Xref "-V" |
| 1027 | .IX Item "-V" |
| 1028 | prints summary of the major perl configuration values and the current |
| 1029 | values of \f(CW@INC\fR. |
| 1030 | .IP "\fB\-V:\fR\fIconfigvar\fR" 5 |
| 1031 | .IX Item "-V:configvar" |
| 1032 | Prints to \s-1STDOUT\s0 the value of the named configuration variable(s), |
| 1033 | with multiples when your configvar argument looks like a regex (has |
| 1034 | non\-letters). For example: |
| 1035 | .Sp |
| 1036 | .Vb 12 |
| 1037 | \& $ perl -V:libc |
| 1038 | \& libc='/lib/libc-2.2.4.so'; |
| 1039 | \& $ perl -V:lib. |
| 1040 | \& libs='-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc'; |
| 1041 | \& libc='/lib/libc-2.2.4.so'; |
| 1042 | \& $ perl -V:lib.* |
| 1043 | \& libpth='/usr/local/lib /lib /usr/lib'; |
| 1044 | \& libs='-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc'; |
| 1045 | \& lib_ext='.a'; |
| 1046 | \& libc='/lib/libc-2.2.4.so'; |
| 1047 | \& libperl='libperl.a'; |
| 1048 | \& .... |
| 1049 | .Ve |
| 1050 | .Sp |
| 1051 | Additionally, extra colons can be used to control formatting. A |
| 1052 | trailing colon suppresses the linefeed and terminator ';', allowing |
| 1053 | you to embed queries into shell commands. (mnemonic: \s-1PATH\s0 separator |
| 1054 | \&':'.) |
| 1055 | .Sp |
| 1056 | .Vb 2 |
| 1057 | \& $ echo "compression-vars: " `perl -V:z.*: ` " are here !" |
| 1058 | \& compression-vars: zcat='' zip='zip' are here ! |
| 1059 | .Ve |
| 1060 | .Sp |
| 1061 | A leading colon removes the 'name=' part of the response, this allows |
| 1062 | you to map to the name you need. (mnemonic: empty label) |
| 1063 | .Sp |
| 1064 | .Vb 2 |
| 1065 | \& $ echo "goodvfork="`./perl -Ilib -V::usevfork` |
| 1066 | \& goodvfork=false; |
| 1067 | .Ve |
| 1068 | .Sp |
| 1069 | Leading and trailing colons can be used together if you need |
| 1070 | positional parameter values without the names. Note that in the case |
| 1071 | below, the \s-1PERL_API\s0 params are returned in alphabetical order. |
| 1072 | .Sp |
| 1073 | .Vb 2 |
| 1074 | \& $ echo building_on `perl -V::osname: -V::PERL_API_.*:` now |
| 1075 | \& building_on 'linux' '5' '1' '9' now |
| 1076 | .Ve |
| 1077 | .IP "\fB\-w\fR" 5 |
| 1078 | .IX Xref "-w" |
| 1079 | .IX Item "-w" |
| 1080 | prints warnings about dubious constructs, such as variable names |
| 1081 | that are mentioned only once and scalar variables that are used |
| 1082 | before being set, redefined subroutines, references to undefined |
| 1083 | filehandles or filehandles opened read-only that you are attempting |
| 1084 | to write on, values used as a number that don't look like numbers, |
| 1085 | using an array as though it were a scalar, if your subroutines |
| 1086 | recurse more than 100 deep, and innumerable other things. |
| 1087 | .Sp |
| 1088 | This switch really just enables the internal \f(CW$^W\fR variable. You |
| 1089 | can disable or promote into fatal errors specific warnings using |
| 1090 | \&\f(CW\*(C`_\|_WARN_\|_\*(C'\fR hooks, as described in perlvar and \*(L"warn\*(R" in perlfunc. |
| 1091 | See also perldiag and perltrap. A new, fine-grained warning |
| 1092 | facility is also available if you want to manipulate entire classes |
| 1093 | of warnings; see warnings or perllexwarn. |
| 1094 | .IP "\fB\-W\fR" 5 |
| 1095 | .IX Xref "-W" |
| 1096 | .IX Item "-W" |
| 1097 | Enables all warnings regardless of \f(CW\*(C`no warnings\*(C'\fR or \f(CW$^W\fR. |
| 1098 | See perllexwarn. |
| 1099 | .IP "\fB\-X\fR" 5 |
| 1100 | .IX Xref "-X" |
| 1101 | .IX Item "-X" |
| 1102 | Disables all warnings regardless of \f(CW\*(C`use warnings\*(C'\fR or \f(CW$^W\fR. |
| 1103 | See perllexwarn. |
| 1104 | .IP "\fB\-x\fR" 5 |
| 1105 | .IX Xref "-x" |
| 1106 | .IX Item "-x" |
| 1107 | .PD 0 |
| 1108 | .IP "\fB\-x\fR \fIdirectory\fR" 5 |
| 1109 | .IX Item "-x directory" |
| 1110 | .PD |
| 1111 | tells Perl that the program is embedded in a larger chunk of unrelated |
| 1112 | \&\s-1ASCII\s0 text, such as in a mail message. Leading garbage will be |
| 1113 | discarded until the first line that starts with #! and contains the |
| 1114 | string \*(L"perl\*(R". Any meaningful switches on that line will be applied. |
| 1115 | If a directory name is specified, Perl will switch to that directory |
| 1116 | before running the program. The \fB\-x\fR switch controls only the |
| 1117 | disposal of leading garbage. The program must be terminated with |
| 1118 | \&\f(CW\*(C`_\|_END_\|_\*(C'\fR if there is trailing garbage to be ignored (the program |
| 1119 | can process any or all of the trailing garbage via the \s-1DATA\s0 filehandle |
| 1120 | if desired). |
| 1121 | .SH "ENVIRONMENT" |
| 1122 | .IX Xref "perl, environment variables" |
| 1123 | .IX Header "ENVIRONMENT" |
| 1124 | .IP "\s-1HOME\s0" 12 |
| 1125 | .IX Xref "HOME" |
| 1126 | .IX Item "HOME" |
| 1127 | Used if chdir has no argument. |
| 1128 | .IP "\s-1LOGDIR\s0" 12 |
| 1129 | .IX Xref "LOGDIR" |
| 1130 | .IX Item "LOGDIR" |
| 1131 | Used if chdir has no argument and \s-1HOME\s0 is not set. |
| 1132 | .IP "\s-1PATH\s0" 12 |
| 1133 | .IX Xref "PATH" |
| 1134 | .IX Item "PATH" |
| 1135 | Used in executing subprocesses, and in finding the program if \fB\-S\fR is |
| 1136 | used. |
| 1137 | .IP "\s-1PERL5LIB\s0" 12 |
| 1138 | .IX Xref "PERL5LIB" |
| 1139 | .IX Item "PERL5LIB" |
| 1140 | A list of directories in which to look for Perl library |
| 1141 | files before looking in the standard library and the current |
| 1142 | directory. Any architecture-specific directories under the specified |
| 1143 | locations are automatically included if they exist. If \s-1PERL5LIB\s0 is not |
| 1144 | defined, \s-1PERLLIB\s0 is used. Directories are separated (like in \s-1PATH\s0) by |
| 1145 | a colon on unixish platforms and by a semicolon on Windows (the proper |
| 1146 | path separator being given by the command \f(CW\*(C`perl \-V:path_sep\*(C'\fR). |
| 1147 | .Sp |
| 1148 | When running taint checks (either because the program was running setuid |
| 1149 | or setgid, or the \fB\-T\fR switch was used), neither variable is used. |
| 1150 | The program should instead say: |
| 1151 | .Sp |
| 1152 | .Vb 1 |
| 1153 | \& use lib "/my/directory"; |
| 1154 | .Ve |
| 1155 | .IP "\s-1PERL5OPT\s0" 12 |
| 1156 | .IX Xref "PERL5OPT" |
| 1157 | .IX Item "PERL5OPT" |
| 1158 | Command-line options (switches). Switches in this variable are taken |
| 1159 | as if they were on every Perl command line. Only the \fB\-[DIMUdmtw]\fR |
| 1160 | switches are allowed. When running taint checks (because the program |
| 1161 | was running setuid or setgid, or the \fB\-T\fR switch was used), this |
| 1162 | variable is ignored. If \s-1PERL5OPT\s0 begins with \fB\-T\fR, tainting will be |
| 1163 | enabled, and any subsequent options ignored. |
| 1164 | .IP "\s-1PERLIO\s0" 12 |
| 1165 | .IX Xref "PERLIO" |
| 1166 | .IX Item "PERLIO" |
| 1167 | A space (or colon) separated list of PerlIO layers. If perl is built |
| 1168 | to use PerlIO system for \s-1IO\s0 (the default) these layers effect perl's \s-1IO\s0. |
| 1169 | .Sp |
| 1170 | It is conventional to start layer names with a colon e.g. \f(CW\*(C`:perlio\*(C'\fR to |
| 1171 | emphasise their similarity to variable \*(L"attributes\*(R". But the code that parses |
| 1172 | layer specification strings (which is also used to decode the \s-1PERLIO\s0 |
| 1173 | environment variable) treats the colon as a separator. |
| 1174 | .Sp |
| 1175 | An unset or empty \s-1PERLIO\s0 is equivalent to \f(CW\*(C`:stdio\*(C'\fR. |
| 1176 | .Sp |
| 1177 | The list becomes the default for \fIall\fR perl's \s-1IO\s0. Consequently only built-in |
| 1178 | layers can appear in this list, as external layers (such as :\fIencoding()\fR) need |
| 1179 | \&\s-1IO\s0 in order to load them!. See \*(L"open pragma\*(R" for how to add external |
| 1180 | encodings as defaults. |
| 1181 | .Sp |
| 1182 | The layers that it makes sense to include in the \s-1PERLIO\s0 environment |
| 1183 | variable are briefly summarised below. For more details see PerlIO. |
| 1184 | .RS 12 |
| 1185 | .IP ":bytes" 8 |
| 1186 | .IX Xref ":bytes" |
| 1187 | .IX Item ":bytes" |
| 1188 | A pseudolayer that turns \fIoff\fR the \f(CW\*(C`:utf8\*(C'\fR flag for the layer below. |
| 1189 | Unlikely to be useful on its own in the global \s-1PERLIO\s0 environment variable. |
| 1190 | You perhaps were thinking of \f(CW\*(C`:crlf:bytes\*(C'\fR or \f(CW\*(C`:perlio:bytes\*(C'\fR. |
| 1191 | .IP ":crlf" 8 |
| 1192 | .IX Xref ":crlf" |
| 1193 | .IX Item ":crlf" |
| 1194 | A layer which does \s-1CRLF\s0 to \*(L"\en\*(R" translation distinguishing \*(L"text\*(R" and |
| 1195 | \&\*(L"binary\*(R" files in the manner of MS-DOS and similar operating systems. |
| 1196 | (It currently does \fInot\fR mimic MS-DOS as far as treating of Control-Z |
| 1197 | as being an end-of-file marker.) |
| 1198 | .IP ":mmap" 8 |
| 1199 | .IX Xref ":mmap" |
| 1200 | .IX Item ":mmap" |
| 1201 | A layer which implements \*(L"reading\*(R" of files by using \f(CW\*(C`mmap()\*(C'\fR to |
| 1202 | make (whole) file appear in the process's address space, and then |
| 1203 | using that as PerlIO's \*(L"buffer\*(R". |
| 1204 | .IP ":perlio" 8 |
| 1205 | .IX Xref ":perlio" |
| 1206 | .IX Item ":perlio" |
| 1207 | This is a re-implementation of \*(L"stdio\-like\*(R" buffering written as a |
| 1208 | PerlIO \*(L"layer\*(R". As such it will call whatever layer is below it for |
| 1209 | its operations (typically \f(CW\*(C`:unix\*(C'\fR). |
| 1210 | .IP ":pop" 8 |
| 1211 | .IX Xref ":pop" |
| 1212 | .IX Item ":pop" |
| 1213 | An experimental pseudolayer that removes the topmost layer. |
| 1214 | Use with the same care as is reserved for nitroglycerin. |
| 1215 | .IP ":raw" 8 |
| 1216 | .IX Xref ":raw" |
| 1217 | .IX Item ":raw" |
| 1218 | A pseudolayer that manipulates other layers. Applying the \f(CW\*(C`:raw\*(C'\fR |
| 1219 | layer is equivalent to calling \f(CW\*(C`binmode($fh)\*(C'\fR. It makes the stream |
| 1220 | pass each byte as-is without any translation. In particular \s-1CRLF\s0 |
| 1221 | translation, and/or :utf8 intuited from locale are disabled. |
| 1222 | .Sp |
| 1223 | Unlike in the earlier versions of Perl \f(CW\*(C`:raw\*(C'\fR is \fInot\fR |
| 1224 | just the inverse of \f(CW\*(C`:crlf\*(C'\fR \- other layers which would affect the |
| 1225 | binary nature of the stream are also removed or disabled. |
| 1226 | .IP ":stdio" 8 |
| 1227 | .IX Xref ":stdio" |
| 1228 | .IX Item ":stdio" |
| 1229 | This layer provides PerlIO interface by wrapping system's \s-1ANSI\s0 C \*(L"stdio\*(R" |
| 1230 | library calls. The layer provides both buffering and \s-1IO\s0. |
| 1231 | Note that \f(CW\*(C`:stdio\*(C'\fR layer does \fInot\fR do \s-1CRLF\s0 translation even if that |
| 1232 | is platforms normal behaviour. You will need a \f(CW\*(C`:crlf\*(C'\fR layer above it |
| 1233 | to do that. |
| 1234 | .IP ":unix" 8 |
| 1235 | .IX Xref ":unix" |
| 1236 | .IX Item ":unix" |
| 1237 | Low level layer which calls \f(CW\*(C`read\*(C'\fR, \f(CW\*(C`write\*(C'\fR and \f(CW\*(C`lseek\*(C'\fR etc. |
| 1238 | .IP ":utf8" 8 |
| 1239 | .IX Xref ":utf8" |
| 1240 | .IX Item ":utf8" |
| 1241 | A pseudolayer that turns on a flag on the layer below to tell perl |
| 1242 | that output should be in utf8 and that input should be regarded as |
| 1243 | already in utf8 form. May be useful in \s-1PERLIO\s0 environment |
| 1244 | variable to make \s-1UTF\-8\s0 the default. (To turn off that behaviour |
| 1245 | use \f(CW\*(C`:bytes\*(C'\fR layer.) |
| 1246 | .IP ":win32" 8 |
| 1247 | .IX Xref ":win32" |
| 1248 | .IX Item ":win32" |
| 1249 | On Win32 platforms this \fIexperimental\fR layer uses native \*(L"handle\*(R" \s-1IO\s0 |
| 1250 | rather than unix-like numeric file descriptor layer. Known to be |
| 1251 | buggy in this release. |
| 1252 | .RE |
| 1253 | .RS 12 |
| 1254 | .Sp |
| 1255 | On all platforms the default set of layers should give acceptable results. |
| 1256 | .Sp |
| 1257 | For \s-1UNIX\s0 platforms that will equivalent of \*(L"unix perlio\*(R" or \*(L"stdio\*(R". |
| 1258 | Configure is setup to prefer \*(L"stdio\*(R" implementation if system's library |
| 1259 | provides for fast access to the buffer, otherwise it uses the \*(L"unix perlio\*(R" |
| 1260 | implementation. |
| 1261 | .Sp |
| 1262 | On Win32 the default in this release is \*(L"unix crlf\*(R". Win32's \*(L"stdio\*(R" |
| 1263 | has a number of bugs/mis\-features for perl \s-1IO\s0 which are somewhat |
| 1264 | C compiler vendor/version dependent. Using our own \f(CW\*(C`crlf\*(C'\fR layer as |
| 1265 | the buffer avoids those issues and makes things more uniform. |
| 1266 | The \f(CW\*(C`crlf\*(C'\fR layer provides \s-1CRLF\s0 to/from \*(L"\en\*(R" conversion as well as |
| 1267 | buffering. |
| 1268 | .Sp |
| 1269 | This release uses \f(CW\*(C`unix\*(C'\fR as the bottom layer on Win32 and so still uses C |
| 1270 | compiler's numeric file descriptor routines. There is an experimental native |
| 1271 | \&\f(CW\*(C`win32\*(C'\fR layer which is expected to be enhanced and should eventually be |
| 1272 | the default under Win32. |
| 1273 | .RE |
| 1274 | .IP "\s-1PERLIO_DEBUG\s0" 12 |
| 1275 | .IX Xref "PERLIO_DEBUG" |
| 1276 | .IX Item "PERLIO_DEBUG" |
| 1277 | If set to the name of a file or device then certain operations of PerlIO |
| 1278 | sub-system will be logged to that file (opened as append). Typical uses |
| 1279 | are \s-1UNIX:\s0 |
| 1280 | .Sp |
| 1281 | .Vb 1 |
| 1282 | \& PERLIO_DEBUG=/dev/tty perl script ... |
| 1283 | .Ve |
| 1284 | .Sp |
| 1285 | and Win32 approximate equivalent: |
| 1286 | .Sp |
| 1287 | .Vb 2 |
| 1288 | \& set PERLIO_DEBUG=CON |
| 1289 | \& perl script ... |
| 1290 | .Ve |
| 1291 | .Sp |
| 1292 | This functionality is disabled for setuid scripts and for scripts run |
| 1293 | with \fB\-T\fR. |
| 1294 | .IP "\s-1PERLLIB\s0" 12 |
| 1295 | .IX Xref "PERLLIB" |
| 1296 | .IX Item "PERLLIB" |
| 1297 | A list of directories in which to look for Perl library |
| 1298 | files before looking in the standard library and the current directory. |
| 1299 | If \s-1PERL5LIB\s0 is defined, \s-1PERLLIB\s0 is not used. |
| 1300 | .IP "\s-1PERL5DB\s0" 12 |
| 1301 | .IX Xref "PERL5DB" |
| 1302 | .IX Item "PERL5DB" |
| 1303 | The command used to load the debugger code. The default is: |
| 1304 | .Sp |
| 1305 | .Vb 1 |
| 1306 | \& BEGIN { require 'perl5db.pl' } |
| 1307 | .Ve |
| 1308 | .IP "\s-1PERL5DB_THREADED\s0" 12 |
| 1309 | .IX Xref "PERL5DB_THREADED" |
| 1310 | .IX Item "PERL5DB_THREADED" |
| 1311 | If set to a true value, indicates to the debugger that the code being |
| 1312 | debugged uses threads. |
| 1313 | .IP "\s-1PERL5SHELL\s0 (specific to the Win32 port)" 12 |
| 1314 | .IX Xref "PERL5SHELL" |
| 1315 | .IX Item "PERL5SHELL (specific to the Win32 port)" |
| 1316 | May be set to an alternative shell that perl must use internally for |
| 1317 | executing \*(L"backtick\*(R" commands or \fIsystem()\fR. Default is \f(CW\*(C`cmd.exe /x/d/c\*(C'\fR |
| 1318 | on WindowsNT and \f(CW\*(C`command.com /c\*(C'\fR on Windows95. The value is considered |
| 1319 | to be space\-separated. Precede any character that needs to be protected |
| 1320 | (like a space or backslash) with a backslash. |
| 1321 | .Sp |
| 1322 | Note that Perl doesn't use \s-1COMSPEC\s0 for this purpose because |
| 1323 | \&\s-1COMSPEC\s0 has a high degree of variability among users, leading to |
| 1324 | portability concerns. Besides, perl can use a shell that may not be |
| 1325 | fit for interactive use, and setting \s-1COMSPEC\s0 to such a shell may |
| 1326 | interfere with the proper functioning of other programs (which usually |
| 1327 | look in \s-1COMSPEC\s0 to find a shell fit for interactive use). |
| 1328 | .IP "\s-1PERL_ALLOW_NON_IFS_LSP\s0 (specific to the Win32 port)" 12 |
| 1329 | .IX Xref "PERL_ALLOW_NON_IFS_LSP" |
| 1330 | .IX Item "PERL_ALLOW_NON_IFS_LSP (specific to the Win32 port)" |
| 1331 | Set to 1 to allow the use of non-IFS compatible \s-1LSP\s0's. |
| 1332 | Perl normally searches for an IFS-compatible \s-1LSP\s0 because this is required |
| 1333 | for its emulation of Windows sockets as real filehandles. However, this may |
| 1334 | cause problems if you have a firewall such as McAfee Guardian which requires |
| 1335 | all applications to use its \s-1LSP\s0 which is not IFS\-compatible, because clearly |
| 1336 | Perl will normally avoid using such an \s-1LSP\s0. |
| 1337 | Setting this environment variable to 1 means that Perl will simply use the |
| 1338 | first suitable \s-1LSP\s0 enumerated in the catalog, which keeps McAfee Guardian |
| 1339 | happy (and in that particular case Perl still works too because McAfee |
| 1340 | Guardian's \s-1LSP\s0 actually plays some other games which allow applications |
| 1341 | requiring \s-1IFS\s0 compatibility to work). |
| 1342 | .IP "\s-1PERL_DEBUG_MSTATS\s0" 12 |
| 1343 | .IX Xref "PERL_DEBUG_MSTATS" |
| 1344 | .IX Item "PERL_DEBUG_MSTATS" |
| 1345 | Relevant only if perl is compiled with the malloc included with the perl |
| 1346 | distribution (that is, if \f(CW\*(C`perl \-V:d_mymalloc\*(C'\fR is 'define'). |
| 1347 | If set, this causes memory statistics to be dumped after execution. If set |
| 1348 | to an integer greater than one, also causes memory statistics to be dumped |
| 1349 | after compilation. |
| 1350 | .IP "\s-1PERL_DESTRUCT_LEVEL\s0" 12 |
| 1351 | .IX Xref "PERL_DESTRUCT_LEVEL" |
| 1352 | .IX Item "PERL_DESTRUCT_LEVEL" |
| 1353 | Relevant only if your perl executable was built with \fB\-DDEBUGGING\fR, |
| 1354 | this controls the behavior of global destruction of objects and other |
| 1355 | references. See \*(L"\s-1PERL_DESTRUCT_LEVEL\s0\*(R" in perlhack for more information. |
| 1356 | .IP "\s-1PERL_DL_NONLAZY\s0" 12 |
| 1357 | .IX Xref "PERL_DL_NONLAZY" |
| 1358 | .IX Item "PERL_DL_NONLAZY" |
| 1359 | Set to one to have perl resolve \fBall\fR undefined symbols when it loads |
| 1360 | a dynamic library. The default behaviour is to resolve symbols when |
| 1361 | they are used. Setting this variable is useful during testing of |
| 1362 | extensions as it ensures that you get an error on misspelled function |
| 1363 | names even if the test suite doesn't call it. |
| 1364 | .IP "\s-1PERL_ENCODING\s0" 12 |
| 1365 | .IX Xref "PERL_ENCODING" |
| 1366 | .IX Item "PERL_ENCODING" |
| 1367 | If using the \f(CW\*(C`encoding\*(C'\fR pragma without an explicit encoding name, the |
| 1368 | \&\s-1PERL_ENCODING\s0 environment variable is consulted for an encoding name. |
| 1369 | .IP "\s-1PERL_HASH_SEED\s0" 12 |
| 1370 | .IX Xref "PERL_HASH_SEED" |
| 1371 | .IX Item "PERL_HASH_SEED" |
| 1372 | (Since Perl 5.8.1.) Used to randomise Perl's internal hash function. |
| 1373 | To emulate the pre\-5.8.1 behaviour, set to an integer (zero means |
| 1374 | exactly the same order as 5.8.0). \*(L"Pre\-5.8.1\*(R" means, among other |
| 1375 | things, that hash keys will be ordered the same between different runs |
| 1376 | of Perl. |
| 1377 | .Sp |
| 1378 | The default behaviour is to randomise unless the \s-1PERL_HASH_SEED\s0 is set. |
| 1379 | If Perl has been compiled with \f(CW\*(C`\-DUSE_HASH_SEED_EXPLICIT\*(C'\fR, the default |
| 1380 | behaviour is \fBnot\fR to randomise unless the \s-1PERL_HASH_SEED\s0 is set. |
| 1381 | .Sp |
| 1382 | If \s-1PERL_HASH_SEED\s0 is unset or set to a non-numeric string, Perl uses |
| 1383 | the pseudorandom seed supplied by the operating system and libraries. |
| 1384 | This means that each different run of Perl will have a different |
| 1385 | ordering of the results of \fIkeys()\fR, \fIvalues()\fR, and \fIeach()\fR. |
| 1386 | .Sp |
| 1387 | \&\fBPlease note that the hash seed is sensitive information\fR. Hashes are |
| 1388 | randomized to protect against local and remote attacks against Perl |
| 1389 | code. By manually setting a seed this protection may be partially or |
| 1390 | completely lost. |
| 1391 | .Sp |
| 1392 | See \*(L"Algorithmic Complexity Attacks\*(R" in perlsec and |
| 1393 | \&\*(L"\s-1PERL_HASH_SEED_DEBUG\s0\*(R" for more information. |
| 1394 | .IP "\s-1PERL_HASH_SEED_DEBUG\s0" 12 |
| 1395 | .IX Xref "PERL_HASH_SEED_DEBUG" |
| 1396 | .IX Item "PERL_HASH_SEED_DEBUG" |
| 1397 | (Since Perl 5.8.1.) Set to one to display (to \s-1STDERR\s0) the value of |
| 1398 | the hash seed at the beginning of execution. This, combined with |
| 1399 | \&\*(L"\s-1PERL_HASH_SEED\s0\*(R" is intended to aid in debugging nondeterministic |
| 1400 | behavior caused by hash randomization. |
| 1401 | .Sp |
| 1402 | \&\fBNote that the hash seed is sensitive information\fR: by knowing it one |
| 1403 | can craft a denial-of-service attack against Perl code, even remotely, |
| 1404 | see \*(L"Algorithmic Complexity Attacks\*(R" in perlsec for more information. |
| 1405 | \&\fBDo not disclose the hash seed\fR to people who don't need to know it. |
| 1406 | See also \fIhash_seed()\fR of Hash::Util. |
| 1407 | .IP "\s-1PERL_ROOT\s0 (specific to the \s-1VMS\s0 port)" 12 |
| 1408 | .IX Xref "PERL_ROOT" |
| 1409 | .IX Item "PERL_ROOT (specific to the VMS port)" |
| 1410 | A translation concealed rooted logical name that contains perl and the |
| 1411 | logical device for the \f(CW@INC\fR path on \s-1VMS\s0 only. Other logical names that |
| 1412 | affect perl on \s-1VMS\s0 include \s-1PERLSHR\s0, \s-1PERL_ENV_TABLES\s0, and |
| 1413 | \&\s-1SYS$TIMEZONE_DIFFERENTIAL\s0 but are optional and discussed further in |
| 1414 | perlvms and in \fI\s-1README\s0.vms\fR in the Perl source distribution. |
| 1415 | .IP "\s-1PERL_SIGNALS\s0" 12 |
| 1416 | .IX Xref "PERL_SIGNALS" |
| 1417 | .IX Item "PERL_SIGNALS" |
| 1418 | In Perls 5.8.1 and later. If set to \f(CW\*(C`unsafe\*(C'\fR the pre\-Perl\-5.8.0 |
| 1419 | signals behaviour (immediate but unsafe) is restored. If set to |
| 1420 | \&\f(CW\*(C`safe\*(C'\fR the safe (or deferred) signals are used. |
| 1421 | See \*(L"Deferred Signals (Safe Signals)\*(R" in perlipc. |
| 1422 | .IP "\s-1PERL_UNICODE\s0" 12 |
| 1423 | .IX Xref "PERL_UNICODE" |
| 1424 | .IX Item "PERL_UNICODE" |
| 1425 | Equivalent to the \fB\-C\fR command-line switch. Note that this is not |
| 1426 | a boolean variable\*(-- setting this to \f(CW"1"\fR is not the right way to |
| 1427 | \&\*(L"enable Unicode\*(R" (whatever that would mean). You can use \f(CW"0"\fR to |
| 1428 | \&\*(L"disable Unicode\*(R", though (or alternatively unset \s-1PERL_UNICODE\s0 in |
| 1429 | your shell before starting Perl). See the description of the \f(CW\*(C`\-C\*(C'\fR |
| 1430 | switch for more information. |
| 1431 | .IP "\s-1SYS$LOGIN\s0 (specific to the \s-1VMS\s0 port)" 12 |
| 1432 | .IX Xref "SYS$LOGIN" |
| 1433 | .IX Item "SYS$LOGIN (specific to the VMS port)" |
| 1434 | Used if chdir has no argument and \s-1HOME\s0 and \s-1LOGDIR\s0 are not set. |
| 1435 | .PP |
| 1436 | Perl also has environment variables that control how Perl handles data |
| 1437 | specific to particular natural languages. See perllocale. |
| 1438 | .PP |
| 1439 | Apart from these, Perl uses no other environment variables, except |
| 1440 | to make them available to the program being executed, and to child |
| 1441 | processes. However, programs running setuid would do well to execute |
| 1442 | the following lines before doing anything else, just to keep people |
| 1443 | honest: |
| 1444 | .PP |
| 1445 | .Vb 3 |
| 1446 | \& $ENV{PATH} = '/bin:/usr/bin'; # or whatever you need |
| 1447 | \& $ENV{SHELL} = '/bin/sh' if exists $ENV{SHELL}; |
| 1448 | \& delete @ENV{qw(IFS CDPATH ENV BASH_ENV)}; |
| 1449 | .Ve |