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1 | =head1 NAME |
2 | |
3 | perlvms - VMS-specific documentation for Perl |
4 | |
5 | =head1 DESCRIPTION |
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6 | |
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7 | Gathered below are notes describing details of Perl 5's |
8 | behavior on VMS. They are a supplement to the regular Perl 5 |
9 | documentation, so we have focussed on the ways in which Perl |
10 | 5 functions differently under VMS than it does under Unix, |
11 | and on the interactions between Perl and the rest of the |
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12 | operating system. We haven't tried to duplicate complete |
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13 | descriptions of Perl features from the main Perl |
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14 | documentation, which can be found in the F<[.pod]> |
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15 | subdirectory of the Perl distribution. |
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16 | |
17 | We hope these notes will save you from confusion and lost |
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18 | sleep when writing Perl scripts on VMS. If you find we've |
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19 | missed something you think should appear here, please don't |
20 | hesitate to drop a line to vmsperl@genetics.upenn.edu. |
21 | |
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22 | =head1 Installation |
23 | |
24 | Directions for building and installing Perl 5 can be found in |
25 | the file F<README.vms> in the main source directory of the |
26 | Perl distribution.. |
27 | |
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28 | =head1 Organization of Perl Images |
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29 | |
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30 | =head2 Core Images |
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31 | |
32 | During the installation process, three Perl images are produced. |
33 | F<Miniperl.Exe> is an executable image which contains all of |
34 | the basic functionality of Perl, but cannot take advantage of |
35 | Perl extensions. It is used to generate several files needed |
36 | to build the complete Perl and various extensions. Once you've |
37 | finished installing Perl, you can delete this image. |
38 | |
39 | Most of the complete Perl resides in the shareable image |
40 | F<PerlShr.Exe>, which provides a core to which the Perl executable |
41 | image and all Perl extensions are linked. You should place this |
42 | image in F<Sys$Share>, or define the logical name F<PerlShr> to |
43 | translate to the full file specification of this image. It should |
44 | be world readable. (Remember that if a user has execute only access |
45 | to F<PerlShr>, VMS will treat it as if it were a privileged shareable |
46 | image, and will therefore require all downstream shareable images to be |
47 | INSTALLed, etc.) |
48 | |
49 | |
50 | Finally, F<Perl.Exe> is an executable image containing the main |
51 | entry point for Perl, as well as some initialization code. It |
52 | should be placed in a public directory, and made world executable. |
53 | In order to run Perl with command line arguments, you should |
54 | define a foreign command to invoke this image. |
55 | |
56 | =head2 Perl Extensions |
57 | |
58 | Perl extensions are packages which provide both XS and Perl code |
59 | to add new functionality to perl. (XS is a meta-language which |
60 | simplifies writing C code which interacts with Perl, see |
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61 | L<perlxs> for more details.) The Perl code for an |
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62 | extension is treated like any other library module - it's |
63 | made available in your script through the appropriate |
64 | C<use> or C<require> statement, and usually defines a Perl |
65 | package containing the extension. |
66 | |
67 | The portion of the extension provided by the XS code may be |
68 | connected to the rest of Perl in either of two ways. In the |
69 | B<static> configuration, the object code for the extension is |
70 | linked directly into F<PerlShr.Exe>, and is initialized whenever |
71 | Perl is invoked. In the B<dynamic> configuration, the extension's |
72 | machine code is placed into a separate shareable image, which is |
73 | mapped by Perl's DynaLoader when the extension is C<use>d or |
74 | C<require>d in your script. This allows you to maintain the |
75 | extension as a separate entity, at the cost of keeping track of the |
76 | additional shareable image. Most extensions can be set up as either |
77 | static or dynamic. |
78 | |
79 | The source code for an extension usually resides in its own |
80 | directory. At least three files are generally provided: |
81 | I<Extshortname>F<.xs> (where I<Extshortname> is the portion of |
82 | the extension's name following the last C<::>), containing |
83 | the XS code, I<Extshortname>F<.pm>, the Perl library module |
84 | for the extension, and F<Makefile.PL>, a Perl script which uses |
85 | the C<MakeMaker> library modules supplied with Perl to generate |
86 | a F<Descrip.MMS> file for the extension. |
87 | |
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88 | =head2 Installing static extensions |
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89 | |
90 | Since static extensions are incorporated directly into |
91 | F<PerlShr.Exe>, you'll have to rebuild Perl to incorporate a |
92 | new extension. You should edit the main F<Descrip.MMS> or F<Makefile> |
93 | you use to build Perl, adding the extension's name to the C<ext> |
94 | macro, and the extension's object file to the C<extobj> macro. |
95 | You'll also need to build the extension's object file, either |
96 | by adding dependencies to the main F<Descrip.MMS>, or using a |
97 | separate F<Descrip.MMS> for the extension. Then, rebuild |
98 | F<PerlShr.Exe> to incorporate the new code. |
99 | |
100 | Finally, you'll need to copy the extension's Perl library |
101 | module to the F<[.>I<Extname>F<]> subdirectory under one |
102 | of the directories in C<@INC>, where I<Extname> is the name |
103 | of the extension, with all C<::> replaced by C<.> (e.g. |
104 | the library module for extension Foo::Bar would be copied |
105 | to a F<[.Foo.Bar]> subdirectory). |
106 | |
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107 | =head2 Installing dynamic extensions |
108 | |
109 | In general, the distributed kit for a Perl extension includes |
110 | a file named Makefile.PL, which is a Perl program which is used |
111 | to create a F<Descrip.MMS> file which can be used to build and |
112 | install the files required by the extension. The kit should be |
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113 | unpacked into a directory tree B<not> under the main Perl source |
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114 | directory, and the procedure for building the extension is simply |
115 | |
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116 | $ perl Makefile.PL ! Create Descrip.MMS |
117 | $ mmk ! Build necessary files |
118 | $ mmk test ! Run test code, if supplied |
119 | $ mmk install ! Install into public Perl tree |
120 | |
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121 | I<N.B.> The procedure by which extensions are built and |
122 | tested creates several levels (at least 4) under the |
123 | directory in which the extension's source files live. |
124 | For this reason, you shouldn't nest the source directory |
125 | too deeply in your directory structure, lest you eccedd RMS' |
126 | maximum of 8 levels of subdirectory in a filespec. (You |
127 | can use rooted logical names to get another 8 levels of |
128 | nesting, if you can't place the files near the top of |
129 | the physical directory structure.) |
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130 | |
131 | VMS support for this process in the current release of Perl |
132 | is sufficient to handle most extensions. However, it does |
133 | not yet recognize extra libraries required to build shareable |
134 | images which are part of an extension, so these must be added |
135 | to the linker options file for the extension by hand. For |
136 | instance, if the F<PGPLOT> extension to Perl requires the |
137 | F<PGPLOTSHR.EXE> shareable image in order to properly link |
138 | the Perl extension, then the line C<PGPLOTSHR/Share> must |
139 | be added to the linker options file F<PGPLOT.Opt> produced |
140 | during the build process for the Perl extension. |
141 | |
142 | By default, the shareable image for an extension is placed |
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143 | F<[.lib.site_perl.auto>I<Arch>.I<Extname>F<]> directory of the |
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144 | installed Perl directory tree (where I<Arch> is F<VMS_VAX> or |
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145 | F<VMS_AXP>, and I<Extname> is the name of the extension, with |
146 | each C<::> translated to C<.>). (See the MakeMaker documentation |
147 | for more details on installation options for extensions.) |
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148 | However, it can be manually placed in any of several locations: |
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149 | - the F<[.Lib.Auto.>I<Arch>I<$PVers>I<Extname>F<]> subdirectory |
150 | of one of the directories in C<@INC> (where I<PVers> |
151 | is the version of Perl you're using, as supplied in C<$]>, |
152 | with '.' converted to '_'), or |
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153 | - one of the directories in C<@INC>, or |
154 | - a directory which the extensions Perl library module |
155 | passes to the DynaLoader when asking it to map |
156 | the shareable image, or |
157 | - F<Sys$Share> or F<Sys$Library>. |
158 | If the shareable image isn't in any of these places, you'll need |
159 | to define a logical name I<Extshortname>, where I<Extshortname> |
160 | is the portion of the extension's name after the last C<::>, which |
161 | translates to the full file specification of the shareable image. |
162 | |
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163 | =head1 File specifications |
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164 | |
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165 | =head2 Syntax |
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166 | |
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167 | We have tried to make Perl aware of both VMS-style and Unix- |
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168 | style file specifications wherever possible. You may use |
169 | either style, or both, on the command line and in scripts, |
170 | but you may not combine the two styles within a single fle |
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171 | specification. VMS Perl interprets Unix pathnames in much |
172 | the same way as the CRTL (I<e.g.> the first component of |
173 | an absolute path is read as the device name for the |
174 | VMS file specification). There are a set of functions |
175 | provided in the C<VMS::Filespec> package for explicit |
176 | interconversion between VMS and Unix syntax; its |
177 | documentation provides more details. |
178 | |
179 | Filenames are, of course, still case-insensitive. For |
180 | consistency, most Perl routines return filespecs using |
181 | lower case letters only, regardless of the case used in |
182 | the arguments passed to them. (This is true only when |
183 | running under VMS; Perl respects the case-sensitivity |
184 | of OSs like Unix.) |
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185 | |
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186 | We've tried to minimize the dependence of Perl library |
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187 | modules on Unix syntax, but you may find that some of these, |
188 | as well as some scripts written for Unix systems, will |
189 | require that you use Unix syntax, since they will assume that |
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190 | '/' is the directory separator, I<etc.> If you find instances |
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191 | of this in the Perl distribution itself, please let us know, |
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192 | so we can try to work around them. |
193 | |
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194 | =head2 Wildcard expansion |
195 | |
196 | File specifications containing wildcards are allowed both on |
197 | the command line and within Perl globs (e.g. <CE<lt>*.cE<gt>>). If |
198 | the wildcard filespec uses VMS syntax, the resultant |
199 | filespecs will follow VMS syntax; if a Unix-style filespec is |
200 | passed in, Unix-style filespecs will be returned. |
201 | |
202 | If the wildcard filespec contains a device or directory |
203 | specification, then the resultant filespecs will also contain |
204 | a device and directory; otherwise, device and directory |
205 | information are removed. VMS-style resultant filespecs will |
206 | contain a full device and directory, while Unix-style |
207 | resultant filespecs will contain only as much of a directory |
208 | path as was present in the input filespec. For example, if |
209 | your default directory is Perl_Root:[000000], the expansion |
210 | of C<[.t]*.*> will yield filespecs like |
211 | "perl_root:[t]base.dir", while the expansion of C<t/*/*> will |
212 | yield filespecs like "t/base.dir". (This is done to match |
213 | the behavior of glob expansion performed by Unix shells.) |
214 | |
215 | Similarly, the resultant filespec will contain the file version |
216 | only if one was present in the input filespec. |
217 | |
218 | =head2 Pipes |
219 | |
220 | Input and output pipes to Perl filehandles are supported; the |
221 | "file name" is passed to lib$spawn() for asynchronous |
222 | execution. You should be careful to close any pipes you have |
223 | opened in a Perl script, lest you leave any "orphaned" |
224 | subprocesses around when Perl exits. |
225 | |
226 | You may also use backticks to invoke a DCL subprocess, whose |
227 | output is used as the return value of the expression. The |
228 | string between the backticks is passed directly to lib$spawn |
229 | as the command to execute. In this case, Perl will wait for |
230 | the subprocess to complete before continuing. |
231 | |
232 | =head1 PERL5LIB and PERLLIB |
233 | |
234 | The PERL5LIB and PERLLIB logical names work as documented L<perl>, |
235 | except that the element separator is '|' instead of ':'. The |
236 | directory specifications may use either VMS or Unix syntax. |
237 | |
238 | =head1 Command line |
239 | |
240 | =head2 I/O redirection and backgrounding |
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241 | |
242 | Perl for VMS supports redirection of input and output on the |
243 | command line, using a subset of Bourne shell syntax: |
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244 | |
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245 | <F<file> reads stdin from F<file>, |
246 | >F<file> writes stdout to F<file>, |
247 | >>F<file> appends stdout to F<file>, |
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248 | 2>F<file> writes stderr to F<file>, and |
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249 | 2>>F<file> appends stderr to F<file>. |
250 | |
251 | In addition, output may be piped to a subprocess, using the |
252 | character '|'. Anything after this character on the command |
253 | line is passed to a subprocess for execution; the subprocess |
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254 | takes the output of Perl as its input. |
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255 | |
256 | Finally, if the command line ends with '&', the entire |
257 | command is run in the background as an asynchronous |
258 | subprocess. |
259 | |
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260 | =head2 Command line switches |
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261 | |
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262 | The following command line switches behave differently under |
263 | VMS than described in L<perlrun>. Note also that in order |
264 | to pass uppercase switches to Perl, you need to enclose |
265 | them in double-quotes on the command line, since the CRTL |
266 | downcases all unquoted strings. |
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267 | |
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268 | =over 4 |
269 | |
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270 | =item -i |
271 | |
272 | If the C<-i> switch is present but no extension for a backup |
273 | copy is given, then inplace editing creates a new version of |
274 | a file; the existing copy is not deleted. (Note that if |
275 | an extension is given, an existing file is renamed to the backup |
276 | file, as is the case under other operating systems, so it does |
277 | not remain as a previous version under the original filename.) |
278 | |
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279 | =item -S |
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280 | |
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281 | If the C<-S> switch is present I<and> the script name does |
282 | not contain a directory, then Perl translates the logical |
283 | name DCL$PATH as a searchlist, using each translation as |
284 | a directory in which to look for the script. In addition, |
285 | if no file type is specified, Perl looks in each directory |
286 | for a file matching the name specified, with a blank type, |
287 | a type of F<.pl>, and a type of F<.com>, in that order. |
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288 | |
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289 | =item -u |
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290 | |
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291 | The C<-u> switch causes the VMS debugger to be invoked |
292 | after the Perl program is compiled, but before it has |
293 | run. It does not create a core dump file. |
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294 | |
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295 | =back |
296 | |
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297 | =head1 Perl functions |
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298 | |
299 | As of the time this document was last revised, the following |
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300 | Perl functions were implemented in the VMS port of Perl |
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301 | (functions marked with * are discussed in more detail below): |
302 | |
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303 | file tests*, abs, alarm, atan, backticks*, binmode*, bless, |
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304 | caller, chdir, chmod, chown, chomp, chop, chr, |
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305 | close, closedir, cos, crypt*, defined, delete, |
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306 | die, do, dump*, each, endpwent, eof, eval, exec*, |
307 | exists, exit, exp, fileno, fork*, getc, getlogin, |
308 | getpwent*, getpwnam*, getpwuid*, glob, gmtime*, goto, |
309 | grep, hex, import, index, int, join, keys, kill*, |
310 | last, lc, lcfirst, length, local, localtime, log, m//, |
311 | map, mkdir, my, next, no, oct, open, opendir, ord, pack, |
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312 | pipe, pop, pos, print, printf, push, q//, qq//, qw//, |
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313 | qx//*, quotemeta, rand, read, readdir, redo, ref, rename, |
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314 | require, reset, return, reverse, rewinddir, rindex, |
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315 | rmdir, s///, scalar, seek, seekdir, select(internal), |
316 | select (system call)*, setpwent, shift, sin, sleep, |
317 | sort, splice, split, sprintf, sqrt, srand, stat, |
318 | study, substr, sysread, system*, syswrite, tell, |
319 | telldir, tie, time, times*, tr///, uc, ucfirst, umask, |
320 | undef, unlink*, unpack, untie, unshift, use, utime*, |
321 | values, vec, wait, waitpid*, wantarray, warn, write, y/// |
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322 | |
323 | The following functions were not implemented in the VMS port, |
324 | and calling them produces a fatal error (usually) or |
325 | undefined behavior (rarely, we hope): |
326 | |
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327 | chroot, dbmclose, dbmopen, fcntl, flock, |
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328 | getpgrp, getppid, getpriority, getgrent, getgrgid, |
329 | getgrnam, setgrent, endgrent, ioctl, link, lstat, |
330 | msgctl, msgget, msgsend, msgrcv, readlink, semctl, |
331 | semget, semop, setpgrp, setpriority, shmctl, shmget, |
332 | shmread, shmwrite, socketpair, symlink, syscall, truncate |
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333 | |
334 | The following functions may or may not be implemented, |
335 | depending on what type of socket support you've built into |
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336 | your copy of Perl: |
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337 | |
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338 | accept, bind, connect, getpeername, |
339 | gethostbyname, getnetbyname, getprotobyname, |
340 | getservbyname, gethostbyaddr, getnetbyaddr, |
341 | getprotobynumber, getservbyport, gethostent, |
342 | getnetent, getprotoent, getservent, sethostent, |
343 | setnetent, setprotoent, setservent, endhostent, |
344 | endnetent, endprotoent, endservent, getsockname, |
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345 | getsockopt, listen, recv, select(system call)*, |
346 | send, setsockopt, shutdown, socket |
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347 | |
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348 | =over 4 |
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349 | |
350 | =item File tests |
351 | |
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352 | The tests C<-b>, C<-B>, C<-c>, C<-C>, C<-d>, C<-e>, C<-f>, |
353 | C<-o>, C<-M>, C<-s>, C<-S>, C<-t>, C<-T>, and C<-z> work as |
354 | advertised. The return values for C<-r>, C<-w>, and C<-x> |
355 | tell you whether you can actually access the file; this may |
356 | not reflect the UIC-based file protections. Since real and |
357 | effective UIC don't differ under VMS, C<-O>, C<-R>, C<-W>, |
358 | and C<-X> are equivalent to C<-o>, C<-r>, C<-w>, and C<-x>. |
359 | Similarly, several other tests, including C<-A>, C<-g>, C<-k>, |
360 | C<-l>, C<-p>, and C<-u>, aren't particularly meaningful under |
361 | VMS, and the values returned by these tests reflect whatever |
362 | your CRTL C<stat()> routine does to the equivalent bits in the |
363 | st_mode field. Finally, C<-d> returns true if passed a device |
364 | specification without an explicit directory (e.g. C<DUA1:>), as |
365 | well as if passed a directory. |
366 | |
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367 | Note: Some sites have reported problems when using the file-access |
368 | tests (C<-r>, C<-w>, and C<-x>) on files accessed via DEC's DFS. |
369 | Specifically, since DFS does not currently provide access to the |
370 | extended file header of files on remote volumes, attempts to |
371 | examine the ACL fail, and the file tests will return false, |
372 | with C<$!> indicating that the file does not exist. You can |
373 | use C<stat> on these files, since that checks UIC-based protection |
374 | only, and then manually check the appropriate bits, as defined by |
375 | your C compiler's F<stat.h>, in the mode value it returns, if you |
376 | need an approximation of the file's protections. |
377 | |
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378 | =item backticks |
379 | |
380 | Backticks create a subprocess, and pass the enclosed string |
381 | to it for execution as a DCL command. Since the subprocess is |
382 | created directly via C<lib$spawn()>, any valid DCL command string |
383 | may be specified. |
384 | |
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385 | =item binmode FILEHANDLE |
386 | |
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387 | The C<binmode> operator will attempt to insure that no translation |
388 | of carriage control occurs on input from or output to this filehandle. |
389 | Since this involves reopening the file and then restoring its |
390 | file position indicator, if this function returns FALSE, the |
391 | underlying filehandle may no longer point to an open file, or may |
392 | point to a different position in the file than before C<binmode> |
393 | was called. |
394 | |
395 | Note that C<binmode> is generally not necessary when using normal |
396 | filehandles; it is provided so that you can control I/O to existing |
397 | record-structured files when necessary. You can also use the |
398 | C<vmsfopen> function in the VMS::Stdio extension to gain finer |
399 | control of I/O to files and devices with different record structures. |
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400 | |
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401 | =item crypt PLAINTEXT, USER |
402 | |
403 | The C<crypt> operator uses the C<sys$hash_password> system |
404 | service to generate the hashed representation of PLAINTEXT. |
405 | If USER is a valid username, the algorithm and salt values |
406 | are taken from that user's UAF record. If it is not, then |
407 | the preferred algorithm and a salt of 0 are used. The |
408 | quadword encrypted value is returned as an 8-character string. |
409 | |
410 | The value returned by C<crypt> may be compared against |
411 | the encrypted password from the UAF returned by the C<getpw*> |
412 | functions, in order to authenticate users. If you're |
413 | going to do this, remember that the encrypted password in |
414 | the UAF was generated using uppercase username and |
415 | password strings; you'll have to upcase the arguments to |
416 | C<crypt> to insure that you'll get the proper value: |
417 | |
418 | sub validate_passwd { |
419 | my($user,$passwd) = @_; |
420 | my($pwdhash); |
421 | if ( !($pwdhash = (getpwnam($user))[1]) || |
422 | $pwdhash ne crypt("\U$passwd","\U$name") ) { |
423 | intruder_alert($name); |
424 | } |
425 | return 1; |
426 | } |
427 | |
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428 | =item dump |
429 | |
430 | Rather than causing Perl to abort and dump core, the C<dump> |
431 | operator invokes the VMS debugger. If you continue to |
432 | execute the Perl program under the debugger, control will |
433 | be transferred to the label specified as the argument to |
434 | C<dump>, or, if no label was specified, back to the |
435 | beginning of the program. All other state of the program |
436 | (I<e.g.> values of variables, open file handles) are not |
437 | affected by calling C<dump>. |
438 | |
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439 | =item exec LIST |
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440 | |
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441 | The C<exec> operator behaves in one of two different ways. |
442 | If called after a call to C<fork>, it will invoke the CRTL |
443 | C<execv()> routine, passing its arguments to the subprocess |
444 | created by C<fork> for execution. In this case, it is |
445 | subject to all limitations that affect C<execv()>. (In |
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446 | particular, this usually means that the command executed in |
447 | the subprocess must be an image compiled from C source code, |
448 | and that your options for passing file descriptors and signal |
449 | handlers to the subprocess are limited.) |
450 | |
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451 | If the call to C<exec> does not follow a call to C<fork>, it |
452 | will cause Perl to exit, and to invoke the command given as |
453 | an argument to C<exec> via C<lib$do_command>. If the argument |
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454 | begins with a '$' (other than as part of a filespec), then it |
455 | is executed as a DCL command. Otherwise, the first token on |
456 | the command line is treated as the filespec of an image to |
457 | run, and an attempt is made to invoke it (using F<.Exe> and |
458 | the process defaults to expand the filespec) and pass the |
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459 | rest of C<exec>'s argument to it as parameters. |
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460 | |
748a9306 |
461 | You can use C<exec> in both ways within the same script, as |
462 | long as you call C<fork> and C<exec> in pairs. Perl |
463 | keeps track of how many times C<fork> and C<exec> have been |
464 | called, and will call the CRTL C<execv()> routine if there have |
465 | previously been more calls to C<fork> than to C<exec>. |
a0d0e21e |
466 | |
467 | =item fork |
468 | |
748a9306 |
469 | The C<fork> operator works in the same way as the CRTL |
470 | C<vfork()> routine, which is quite different under VMS than |
471 | under Unix. Specifically, while C<fork> returns 0 after it |
472 | is called and the subprocess PID after C<exec> is called, in |
a0d0e21e |
473 | both cases the thread of execution is within the parent |
474 | process, so there is no opportunity to perform operations in |
748a9306 |
475 | the subprocess before calling C<exec>. |
a0d0e21e |
476 | |
748a9306 |
477 | In general, the use of C<fork> and C<exec> to create |
a0d0e21e |
478 | subprocess is not recommended under VMS; wherever possible, |
748a9306 |
479 | use the C<system> operator or piped filehandles instead. |
480 | |
481 | =item getpwent |
c07a80fd |
482 | |
748a9306 |
483 | =item getpwnam |
c07a80fd |
484 | |
748a9306 |
485 | =item getpwuid |
486 | |
487 | These operators obtain the information described in L<perlfunc>, |
488 | if you have the privileges necessary to retrieve the named user's |
489 | UAF information via C<sys$getuai>. If not, then only the C<$name>, |
490 | C<$uid>, and C<$gid> items are returned. The C<$dir> item contains |
491 | the login directory in VMS syntax, while the C<$comment> item |
492 | contains the login directory in Unix syntax. The C<$gcos> item |
493 | contains the owner field from the UAF record. The C<$quota> |
494 | item is not used. |
a0d0e21e |
495 | |
e518068a |
496 | =item gmtime |
497 | |
498 | The C<gmtime> operator will function properly if you have a |
499 | working CRTL C<gmtime()> routine, or if the logical name |
500 | SYS$TIMEZONE_DIFFERENTIAL is defined as the number of seconds |
501 | which must be added to UTC to yield local time. (This logical |
502 | name is defined automatically if you are running a version of |
503 | VMS with built-in UTC support.) If neither of these cases is |
504 | true, a warning message is printed, and C<undef> is returned. |
505 | |
506 | =item kill |
507 | |
508 | In most cases, C<kill> kill is implemented via the CRTL's C<kill()> |
509 | function, so it will behave according to that function's |
510 | documentation. If you send a SIGKILL, however, the $DELPRC system |
10a676f8 |
511 | service is called directly. This insures that the target |
e518068a |
512 | process is actually deleted, if at all possible. (The CRTL's C<kill()> |
513 | function is presently implemented via $FORCEX, which is ignored by |
514 | supervisor-mode images like DCL.) |
515 | |
516 | Also, negative signal values don't do anything special under |
517 | VMS; they're just converted to the corresponding positive value. |
518 | |
4fdae800 |
519 | =item qx// |
520 | |
521 | See the entry on C<backticks> above. |
522 | |
e518068a |
523 | =item select (system call) |
524 | |
525 | If Perl was not built with socket support, the system call |
526 | version of C<select> is not available at all. If socket |
527 | support is present, then the system call version of |
528 | C<select> functions only for file descriptors attached |
529 | to sockets. It will not provide information about regular |
530 | files or pipes, since the CRTL C<select()> routine does not |
531 | provide this functionality. |
532 | |
748a9306 |
533 | =item stat EXPR |
a0d0e21e |
534 | |
748a9306 |
535 | Since VMS keeps track of files according to a different scheme |
536 | than Unix, it's not really possible to represent the file's ID |
537 | in the C<st_dev> and C<st_ino> fields of a C<struct stat>. Perl |
538 | tries its best, though, and the values it uses are pretty unlikely |
539 | to be the same for two different files. We can't guarantee this, |
540 | though, so caveat scriptor. |
541 | |
542 | =item system LIST |
543 | |
544 | The C<system> operator creates a subprocess, and passes its |
a0d0e21e |
545 | arguments to the subprocess for execution as a DCL command. |
e518068a |
546 | Since the subprocess is created directly via C<lib$spawn()>, any |
748a9306 |
547 | valid DCL command string may be specified. If LIST consists |
548 | of the empty string, C<system> spawns an interactive DCL subprocess, |
549 | in the same fashion as typiing B<SPAWN> at the DCL prompt. |
550 | Perl waits for the subprocess to complete before continuing |
4fdae800 |
551 | execution in the current process. As described in L<perlfunc>, |
552 | the return value of C<system> is a fake "status" which follows |
553 | POSIX semantics; see the description of C<$?> in this document |
554 | for more detail. The actual VMS exit status of the subprocess |
555 | is available in C<$^S> (as long as you haven't used another Perl |
556 | function that resets C<$?> and C<$^S> in the meantime). |
a0d0e21e |
557 | |
1c9f8daa |
558 | =item time |
559 | |
560 | The value returned by C<time> is the offset in seconds from |
561 | 01-JAN-1970 00:00:00 (just like the CRTL's times() routine), in order |
562 | to make life easier for code coming in from the POSIX/Unix world. |
563 | |
a0d0e21e |
564 | =item times |
565 | |
748a9306 |
566 | The array returned by the C<times> operator is divided up |
567 | according to the same rules the CRTL C<times()> routine. |
a0d0e21e |
568 | Therefore, the "system time" elements will always be 0, since |
569 | there is no difference between "user time" and "system" time |
570 | under VMS, and the time accumulated by subprocess may or may |
571 | not appear separately in the "child time" field, depending on |
748a9306 |
572 | whether L<times> keeps track of subprocesses separately. Note |
573 | especially that the VAXCRTL (at least) keeps track only of |
574 | subprocesses spawned using L<fork> and L<exec>; it will not |
575 | accumulate the times of suprocesses spawned via pipes, L<system>, |
576 | or backticks. |
577 | |
16d20bd9 |
578 | =item unlink LIST |
579 | |
580 | C<unlink> will delete the highest version of a file only; in |
581 | order to delete all versions, you need to say |
582 | 1 while (unlink LIST); |
583 | You may need to make this change to scripts written for a |
584 | Unix system which expect that after a call to C<unlink>, |
585 | no files with the names passed to C<unlink> will exist. |
4633a7c4 |
586 | (Note: This can be changed at compile time; if you |
587 | C<use Config> and C<$Config{'d_unlink_all_versions'}> is |
588 | C<define>, then C<unlink> will delete all versions of a |
589 | file on the first call.) |
16d20bd9 |
590 | |
591 | C<unlink> will delete a file if at all possible, even if it |
592 | requires changing file protection (though it won't try to |
593 | change the protection of the parent directory). You can tell |
594 | whether you've got explicit delete access to a file by using the |
595 | C<VMS::Filespec::candelete> operator. For instance, in order |
596 | to delete only files to which you have delete access, you could |
597 | say something like |
4e592037 |
598 | |
16d20bd9 |
599 | sub safe_unlink { |
600 | my($file,$num); |
601 | foreach $file (@_) { |
602 | next unless VMS::Filespec::candelete($file); |
603 | $num += unlink $file; |
604 | } |
605 | $num; |
606 | } |
4e592037 |
607 | |
608 | (or you could just use C<VMS::Stdio::remove>, if you've installed |
609 | the VMS::Stdio extension distributed with Perl). If C<unlink> has to |
610 | change the file protection to delete the file, and you interrupt it |
611 | in midstream, the file may be left intact, but with a changed ACL |
612 | allowing you delete access. |
16d20bd9 |
613 | |
748a9306 |
614 | =item utime LIST |
615 | |
616 | Since ODS-2, the VMS file structure for disk files, does not keep |
617 | track of access times, this operator changes only the modification |
618 | time of the file (VMS revision date). |
619 | |
620 | =item waitpid PID,FLAGS |
621 | |
622 | If PID is a subprocess started by a piped L<open>, C<waitpid> |
623 | will wait for that subprocess, and return its final |
624 | status value. If PID is a subprocess created in some other way |
625 | (e.g. SPAWNed before Perl was invoked), or is not a subprocess of |
626 | the current process, C<waitpid> will check once per second whether |
627 | the process has completed, and when it has, will return 0. (If PID |
628 | specifies a process that isn't a subprocess of the current process, |
629 | and you invoked Perl with the C<-w> switch, a warning will be issued.) |
630 | |
631 | The FLAGS argument is ignored in all cases. |
a0d0e21e |
632 | |
55497cff |
633 | =back |
634 | |
a5f75d66 |
635 | =head1 Perl variables |
636 | |
55497cff |
637 | The following VMS-specific information applies to the indicated |
638 | "special" Perl variables, in addition to the general information |
639 | in L<perlvar>. Where there is a conflict, this infrmation |
640 | takes precedence. |
641 | |
642 | =over 4 |
643 | |
a5f75d66 |
644 | =item %ENV |
645 | |
646 | Reading the elements of the %ENV array returns the |
647 | translation of the logical name specified by the key, |
648 | according to the normal search order of access modes and |
649 | logical name tables. If you append a semicolon to the |
650 | logical name, followed by an integer, that integer is |
651 | used as the translation index for the logical name, |
652 | so that you can look up successive values for search |
653 | list logical names. For instance, if you say |
654 | |
655 | $ Define STORY once,upon,a,time,there,was |
656 | $ perl -e "for ($i = 0; $i <= 6; $i++) " - |
740ce14c |
657 | _$ -e "{ print $ENV{'story;'.$i},' '}" |
a5f75d66 |
658 | |
659 | Perl will print C<ONCE UPON A TIME THERE WAS>. |
660 | |
661 | The %ENV keys C<home>, C<path>,C<term>, and C<user> |
662 | return the CRTL "environment variables" of the same |
663 | names, if these logical names are not defined. The |
664 | key C<default> returns the current default device |
665 | and directory specification, regardless of whether |
666 | there is a logical name DEFAULT defined.. |
667 | |
668 | Setting an element of %ENV defines a supervisor-mode logical |
669 | name in the process logical name table. C<Undef>ing or |
670 | C<delete>ing an element of %ENV deletes the equivalent user- |
671 | mode or supervisor-mode logical name from the process logical |
672 | name table. If you use C<undef>, the %ENV element remains |
673 | empty. If you use C<delete>, another attempt is made at |
674 | logical name translation after the deletion, so an inner-mode |
675 | logical name or a name in another logical name table will |
676 | replace the logical name just deleted. It is not possible |
677 | at present to define a search list logical name via %ENV. |
678 | |
740ce14c |
679 | At present, the first time you iterate over %ENV using |
edc7bc49 |
680 | C<keys>, or C<values>, you will incur a time penalty as all |
681 | logical names are read, in order to fully populate %ENV. |
682 | Subsequent iterations will not reread logical names, so they |
683 | won't be as slow, but they also won't reflect any changes |
684 | to logical name tables caused by other programs. The C<each> |
685 | operator is special: it returns each element I<already> in |
686 | %ENV, but doesn't go out and look for more. Therefore, if |
687 | you've previously used C<keys> or C<values>, you'll see all |
688 | the logical names visible to your process, and if not, you'll |
689 | see only the names you've looked up so far. (This is a |
690 | consequence of the way C<each> is implemented now, and it |
691 | may change in the future, so it wouldn't be a good idea |
692 | to rely on it too much.) |
740ce14c |
693 | |
a5f75d66 |
694 | In all operations on %ENV, the key string is treated as if it |
695 | were entirely uppercase, regardless of the case actually |
696 | specified in the Perl expression. |
697 | |
a5f75d66 |
698 | =item $! |
699 | |
700 | The string value of C<$!> is that returned by the CRTL's |
701 | strerror() function, so it will include the VMS message for |
702 | VMS-specific errors. The numeric value of C<$!> is the |
703 | value of C<errno>, except if errno is EVMSERR, in which |
704 | case C<$!> contains the value of vaxc$errno. Setting C<$!> |
4e592037 |
705 | always sets errno to the value specified. If this value is |
706 | EVMSERR, it also sets vaxc$errno to 4 (NONAME-F-NOMSG), so |
707 | that the string value of C<$!> won't reflect the VMS error |
708 | message from before C<$!> was set. |
709 | |
710 | =item $^E |
711 | |
712 | This variable provides direct access to VMS status values |
713 | in vaxc$errno, which are often more specific than the |
714 | generic Unix-style error messages in C<$!>. Its numeric value |
715 | is the value of vaxc$errno, and its string value is the |
716 | corresponding VMS message string, as retrieved by sys$getmsg(). |
717 | Setting C<$^E> sets vaxc$errno to the value specified. |
718 | |
4fdae800 |
719 | =item $? |
720 | |
721 | The "status value" returned in C<$?> is synthesized from the |
722 | actual exit status of the subprocess in a way that approximates |
723 | POSIX wait(5) semantics, in order to allow Perl programs to |
724 | portably test for successful completion of subprocesses. The |
725 | low order 8 bits of C<$?> are always 0 under VMS, since the |
726 | termination status of a process may or may not have been |
727 | generated by an exception. The next 8 bits are derived from |
728 | severity portion of the subprocess' exit status: if the |
729 | severity was success or informational, these bits are all 0; |
730 | otherwise, they contain the severity value shifted left one bit. |
731 | As a result, C<$?> will always be zero if the subprocess' exit |
732 | status indicated successful completion, and non-zero if a |
733 | warning or error occurred. The actual VMS exit status may |
734 | be found in C<$^S> (q.v.). |
735 | |
736 | =item $^S |
737 | |
738 | Under VMS, this is the 32-bit VMS status value returned by the |
739 | last subprocess to complete. Unlink C<$?>, no manipulation |
740 | is done to make this look like a POSIX wait(5) value, so it |
741 | may be treated as a normal VMS status value. |
742 | |
4e592037 |
743 | =item $| |
744 | |
745 | Setting C<$|> for an I/O stream causes data to be flushed |
746 | all the way to disk on each write (I<i.e.> not just to |
747 | the underlying RMS buffers for a file). In other words, |
748 | it's equivalent to calling fflush() and fsync() from C. |
a5f75d66 |
749 | |
55497cff |
750 | =back |
751 | |
748a9306 |
752 | =head1 Revision date |
a0d0e21e |
753 | |
4e592037 |
754 | This document was last updated on 28-Feb-1996, for Perl 5, |
e518068a |
755 | patchlevel 2. |
756 | |
757 | =head1 AUTHOR |
758 | |
759 | Charles Bailey bailey@genetics.upenn.edu |
760 | |