1PERLDL(1) User Contributed Perl Documentation PERLDL(1)
2
6 perldl - Simple shell for PDL (see also pdl2)
7
9 Use PDL interactively:
10 bash$ perldl
12 pdl> $x = sequence(10) # or any other perl or PDL command
13 bash$ pdl
15 pdl> print "Hello, world!\n";
16 pdl> with_time { print +($A->matmult($B))->info, "\n" } for 1..5;
18 Run a script:
20 bash$ cat > pdlscript
22 #!/usr/bin/pdl
23 print "Hello, world!\n";
24 ...
25
27 The program perldl is a simple shell (written in perl) for interactive
28 use of PDL. It consists of a command-line interface that supports
29 immediate interpretation of perl commands and expressions. Perl
30 expressions, including PDL constructs, can be entered directly at the
31 keyboard and are compiled and executed immediately. The syntax is not
32 exactly identical to Perl, in that under most circumstances ending a
33 line causes immediate execution of the command entered so far (no
34 trailing ';' is required).
35 The synonym pdl is a compiled executable that is useful as a script
37 interpreter using UNIX shebang ("#!") syntax. This is useful for
38 generating and re-executing command-journal files from perldl.
39 The perldl shell runs an initial startup file ("~/.perldlrc") that can
41 be used to pre-load perl modules or configure the global perl
42 environment. It features a path mechanism for autoloading perl
43 subroutines. There is a command-history mechanism, and several other
44 useful features such as command preprocessing, shortcuts for commonly
45 used commands such as "print", and the ability to execute arbitrary
46 code whenever a prompt is printed.
47 Depending on your configuration settings, perldl can be set to honor or
49 ignore the ^D (end-of-file) character when sent from a terminal, or to
50 attempt to do the Right Thing when a block construct spanning multiple
51 lines is encountered.
52 perldl and pdl support several command-line options, which are
54 discussed near the end of this document.
55 Reference manual & online help
57 The PDL reference manual and online help are available from within
58 perldl, using the help and apropos commands (which may also be
59 abbreviated ? and ??.) The help command alone prints a summary of
60 help syntax, and help <module-name> will print POD documentation from
61 the module you mention (POD is the Perl format for embedding
62 documentation in your perl code; see perlpod for details).
63 If you include POD documentation in your autoload subroutines (see path
65 mechanism below), then both help and apropos will find it and be able
66 to format and display it on demand.
67 History mechanism
69 If you have the perl modules ReadLines and ReadKeys installed, then
70 perldl supports a history and line-editing mechanism using editing keys
71 similar to "emacs". The last 500 commands are always stored in the file
72 .perldl_hist in your home directory between sessions. Set
73 $PERLDL::HISTFILESIZE to change the number of lines saved. The command
74 "l [number]" shows you the last "number" commands you typed where
75 "number" defaults to 20.
76 e.g.:
78 bash$ perldl
80 ReadLines enabled
81 pdl> $x = rfits "foo.fits"
82 BITPIX = -32 size = 88504 pixels
83 Reading 354016 bytes
84 BSCALE = && BZERO =
85 pdl> imag log($x+400)
87 Displaying 299 x 296 image from 4.6939525604248 to 9.67116928100586 ...
88 Command execution
90 If you enter a simple command at the perldl command line, it is
91 immediately executed in a Perl eval(). The environment is almost
92 identical to that within a perl script, with some important exceptions:
93 • $_ is not preserved across lines
95 $_ is used to hold the command line for initial processing, so at
97 the beginning of processing of each command line, $_ contains the
98 command itself. Use variables other than $_ to store values across
99 lines.
100 • Scope is not preserved across lines
102 Each command line is executed in a separate "eval" block within
104 perl, so scoping commands such as "my" and "local" may not perform
105 exactly as expected -- in particular, if you declare a variable with
106 "my", it is local to the particular command line on which you typed
107 the "my" command, which means that it will evaporate before the next
108 prompt is printed. (You can use "my" variables in a multi-line
109 block or to isolate values within a single command line, of course).
110 NOTE: pdl2 preserves lexical scope between lines.
112 • Execution is immediate
114 Under most circumstances, as soon as you end a line of input the
116 line is parsed and executed. This breaks Perl's normal dependence
117 on semicolons as command delimiters. For example, the two-line
118 expression
119 print "Hello ",
121 "world";
122 prints the phrase "Hello world" in Perl, but (under most
124 circumstances) "Hello " in perldl.
125 • Multi-line execution
127 In multiline mode (which is enabled by default, see Shell variables,
129 below), perldl searches for searches for block-like constructs with
130 curly braces, parentheses, quotes, and related delimiters. If you
131 leave such a construct open, perldl accepts more lines of input
132 until you close the construct or explicitly end the multi-line
133 expression with ^D. Following the example above, the phrase
134 { print "Hello ",
136 "world"; }
137 will print "Hello world" from either Perl or (in multi-line mode)
139 perldl.
140 Warning: The multi-line parsing uses Damian Conway's Text::Balanced
142 module, which contains some flaws -- so it can be fooled by quote-
143 like operators such as "q/.../", included POD documentation, multi-
144 line "<<" quotes, and some particularly bizarre-but-valid "m/.../"
145 matches and "s/.../.../" substitutions. In such cases, use ^D to
146 close out the multi-line construct and force compilation-and-
147 execution.
148 If you want to preserve this behavior in a script (for example to
150 replay a command journal file; see below on how to create one), you can
151 use pdl instead of perl as the interpreter in the script's initial
152 shebang line.
153 Terminating "perldl"
155 A "perldl" session can be terminated with any of the commands "quit",
156 "exit" or the shorthands "x" or "q". If EOF handling is switched on
157 (the default) you can also type ^D at the command prompt.
158 If the command input is NOT a terminal (for example if you are running
160 from a command journal file), then EOF will always terminate perldl.
161 Terminating commands (Ctrl-C handling)
163 Commands executed within "perldl" can be terminated prematurely using
164 "Ctrl-C" (or whichever key sequence sends an INT signal to the process
165 on your terminal). Provided your PDL code does not ignore "sigint"s
166 this should throw you back at the "perldl" command prompt:
167 pdl> $result = start_lengthy_computation()
169 <Ctrl-C>
170 Ctrl-C detected
171 pdl>
173 As of 2.077, this requires Sys::SigAction to be installed (without
175 that, and before 2.077, for Perl >5.8 it didn't actually interrupt
176 things).
177 Shortcuts and aliases
179 • The shell aliases "p" to be a convenient short form of "print",
180 e.g.
181 pdl> p ones 5,3
183 [
185 [1 1 1 1 1]
186 [1 1 1 1 1]
187 [1 1 1 1 1]
188 ]
189 • "q" and "x" are short-hand for "quit".
191 • "l" lists the history buffer
193 pdl> l # list last 20 commands
195 pdl> l 40 # list last 40 commands
197 • "?" is an alias for help
199 pdl> ? pdl2 # get help for new pdl2 shell
201 • "??" is an alias for apropos
203 pdl> ?? PDL::Doc
205 • help, apropos, usage and sig: all words after these commands are
207 used verbatim and not evaluated by perl. So you can write, e.g.,
208 pdl> help help
210 instead of
212 pdl> help 'help'
214 • "with_time" runs the following code-block, and tells you how long
216 it took, in milliseconds. Requires Time::HiRes.
217 pdl> with_time { print +($A->matmult($B))->info, "\n" } for 1..5;
219 Command-line options
221 perldl and pdl support several command-line options to adjust the
222 behavior of the session. Most of them are equivalent to commands that
223 can be entered at the pdl> prompt. They are:
224 -glut
226 Load OpenGL when starting the shell (the perl OpenGL module, which
227 is available from CPAN must be installed). This enables readline
228 event loop processing. Don't use with -tk.
229 -tk Load Tk when starting the shell (the perl Tk module, which is
231 available from CPAN must be installed). This enables readline
232 event loop processing. Don't use with -glut.
233 -f file
235 Loads the file before processing any user input. Any errors during
236 the execution of the file are fatal.
237 -w Runs with warning messages (i.e. the normal perl "-w" warnings)
239 turned-on.
240 -M module
242 Loads the module before processing any user input. Compare
243 corresponding "perl" switch.
244 -m module
246 Unloads the module before processing any user input.
247 -I directory
249 Adds directory to the include path. (i.e. the @INC array) Compare
250 corresponding "perl" switch.
251 -V Prints a summary of PDL config. This information should be included
253 with any PDL bug report. Compare corresponding "perl" switch.
254 The startup file ~/.perldlrc
256 If the file ~/.perldlrc is found it is sourced at start-up to load
257 default modules, set shell variables, etc. If it is NOT found the
258 distribution file PDL/default.perldlrc is read instead. This loads
259 various modules considered useful by default, and which ensure
260 compatibility with v1.11. If you don't like this and want a more
261 streamlined set of your own favourite modules simple create your own
262 ~/.perldlrc. You may wish to start from the existing
263 PDL/default.perldlrc as a template since it will not be sourced once
264 you replace it with your own version.
265 To set even more local defaults the file local.perldlrc (in the
267 current directory) is sourced if found. This lets you load modules and
268 define subroutines for the project in the current directory.
269 The name is chosen specifically because it was found hidden files were
271 NOT wanted in these circumstances.
272 The startup file should normally include "use PDL::AutoLoader;", as
274 many of the nicer interactive features won't work without it.
275 Shell variables
277 Shell variables: (Note: if you don't like the defaults change them in
278 ~/.perldlrc)
279 • $PERLDL::ESCAPE - default value '#'
281 Any line starting with this character is treated as a shell escape.
283 The default value is chosen because it escapes the code from the
284 standard perl interpreter.
285 • $PERLDL::HISTFILESIZE - default value 500
287 This is the number of lines of perldl shell command history to
289 keep.
290 • $PERLDL::PAGER - default value "more"
292 External program to filter the output of commands. Using "more"
294 prints output one screenful at a time. On Unix, setting page(1)
295 and $PERLDL::PAGER to "tee -a outfile" will keep a record of the
296 output generated by subsequent perldl commands (without paging).
297 • $PERLDL::PROMPT - default value 'pdl> '
299 Enough said But can also be set to a subroutine reference, e.g.
301 $PERLDL::PROMPT = sub {join(':',(gmtime)[2,1,0]).'> '} puts the
302 current time into the prompt.
303 • $PERLDL::MULTI - default value 1
305 If this is set to a true value, then perldl will parse multi-line
307 perl blocks: your input will not be executed until you finish a
308 line with no outstanding group operators (such as quotes, blocks,
309 parenthesis, or brackets) still active. Continuation lines have a
310 different prompt that shows you what delimiters are still active.
311 Note that this is not (yet!) a complete perl parser. In
313 particular, Text::Balanced appears to be able to ignore quoting
314 operatores like "q/ ... /" within a line, but not to be able to
315 extend them across lines. Likewise, there is no support for the
316 '<<' operator.
317 Multiline conventional strings and {}, [], and () groupings are
319 well supported.
320 • $PERLDL::NO_EOF - default value 0 / 1 on MSWin32
322 Protects against accidental use of "^D" from the terminal. If this
324 is set to a true value, then you can't accidentally exit perldl by
325 typing "^D". If you set it to a value larger than 1 (and
326 PERLDL::MULTI is set), then you can't use "^D" to exit multiline
327 commands either. If you're piping commands in from a file or pipe,
328 this variable has no effect.
329 • $HOME
331 The user's home directory
333 • $PERLDL::TERM
335 This is the Term::ReadLine object associated with the perldl shell.
337 It can be used by routines called from perldl if your command is
338 interactive.
339 • $PDL::toolongtoprint
341 The maximal size pdls to print (defaults to 10,000 elements). This
343 is not just a "perldl" or "pdl2" variable but it is something that
344 is usually needed in an interactive debugging session.
345 Executing scripts from the "perldl" prompt
347 A useful idiom for developing perldl scripts or editing functions on-
348 line is
349 pdl> # emacs script &
351 -- add perldl code to script and save the file
352 pdl> do 'script'
354 -- substitute your favourite window-based editor for 'emacs' (you may
356 also need to change the '&' on non-Unix systems).
357 Running "do 'script'" again updates any variables and function
359 definitions from the current version of 'script'.
360 Executing perldl scripts from the command line
362 PDL scripts are just perl scripts that happen to use PDL (and possibly
363 PDL::NiceSlice). But for the truly lazy, perldl can be invokes as a
364 script interpreter. Because perldl is itself an interpreted perl
365 script, most unices won't allow you to say "#!/usr/bin/perldl" at the
366 top of your script.
367 Instead, say "#!/usr/bin/pdl" and your script will be executed exactly
369 as if you typed it, line-by-line, into the perldl shell.
370 Command preprocessing
372 NOTE: This feature is used by default by PDL::NiceSlice. See below for
373 more about slicing at the "perldl" prompt
374 In some cases, it is convenient to process commands before they are
376 sent to perl for execution. For example, this is the case where the
377 shell is being presented to people unfamiliar with perl but who wish to
378 take advantage of commands added locally (eg by automatically quoting
379 arguments to certain commands).
380 *NOTE*: The preprocessing interface has changed from earlier versions!
382 The old way using $PERLDL::PREPROCESS will still work but is strongly
383 deprecated and might go away in the future.
384 You can enable preprocessing by registering a filter with the
386 "preproc_add" function. "preproc_add" takes one argument which is the
387 filter to be installed. A filter is a Perl code reference (usually set
388 in a local configuration file) that will be called, with the current
389 command string as argument, just prior to the string being executed by
390 the shell. The modified string should be returned. Note that you can
391 make "perldl" completely unusable if you fail to return the modified
392 string; quitting is then your only option.
393 Filters can be removed from the preprocessing pipeline by calling
395 "preproc_del" with the filter to be removed as argument. To find out
396 if a filter is currently installed in the preprocessing pipeline use
397 "preproc_registered":
398 pdl> preproc_add $myfilter unless preproc_registered $myfilter;
400 Previous versions of "perldl" used the variable $PERLDL::PREPROCESS.
402 This will still work but should be avoided. Please change your scripts
403 to use the "preproc_add" etc functions.
404 The following code would check for a call to function 'mysub' and
406 bracket arguments with qw.
407 $filter = preproc_add sub {
409 my $str = shift;
410 $str =~ s/^\s+//; # Strip leading space
411 if ($str =~ /^mysub/) {
412 my ($command, $arguments) = split(/\s+/,$str, 2);
413 $str = "$command qw( $arguments )"
414 if (defined $arguments && $arguments !~ /^qw/);
415 };
416 # Return the input string, modified as required
417 return $str;
418 };
419 This would convert:
421 pdl> mysub arg1 arg2
423 to
425 pdl> mysub qw( arg1 arg2 )
427 which Perl will understand as a list. Obviously, a little more effort
429 is required to check for cases where the caller has supplied a normal
430 list (and so does not require automatic quoting) or variable
431 interpolation is required.
432 You can remove this preprocessor using the "preproc_del" function which
434 takes one argument (the filter to be removed, it must be the same
435 coderef that was returned from a previous "preproc_add" call):
436 pdl> preproc_del $filter;
438 An example of actual usage can be found in the "perldl" script. Look at
440 the function "trans" to see how the niceslicing preprocessor is
441 enabled/disabled.
442 "perldl" and PDL::NiceSlice
444 PDL::NiceSlice introduces a more convenient slicing syntax for
445 ndarrays. In current versions of "perldl" and "pdl2" niceslicing is
446 enabled by default (if the required CPAN modules are installed on your
447 machine).
448 At startup "perldl" will let you know if niceslicing is enabled. The
450 startup message will contain info to this end, something like this:
451 perlDL shell v1.XX
453 PDL comes with ABSOLUTELY NO WARRANTY. For details, see the file
454 'COPYING' in the PDL distribution. This is free software and you
455 are welcome to redistribute it under certain conditions, see
456 the same file for details.
457 ReadLines, NiceSlice enabled
458 Reading /home/csoelle/.perldlrc...
459 Type 'demo' for online demos
460 Loaded PDL v2.XX
461 When you get such a message that indicates "NiceSlice" is enabled you
463 can use the enhanced slicing syntax:
464 pdl> $x = sequence 10;
466 pdl> p $x(3:8:2)
467 For details consult PDL::NiceSlice.
469 PDL::NiceSlice installs a filter in the preprocessing pipeline (see
471 above) to enable the enhanced slicing syntax. You can use a few
472 commands in the "perldl" shell to switch this preprocessing on or off
473 and also explicitly check the substitutions that the NiceSlice filter
474 makes.
475 You can switch the PDL::NiceSlice filter on and off by typing
477 pdl> trans # switch niceslicing on
479 and
481 pdl> notrans # switch niceslicing off
483 respectively. The filter is on by default.
485 To see how your commands are translated switch reporting on:
487 pdl> report 1;
489 pdl> p $x(3:8:2)
490 processed p $x->slice([3,8,2])
491 [3 5 7]
492 Similarly, switch reporting off as needed
494 pdl> report 0;
496 pdl> p $x(3:8:2)
497 [3 5 7]
498 Reporting is off by default.
500 Automatically execute your own hooks
502 The variable @PERLDL::AUTO is a simple list of perl code strings and/or
503 code reference. It is used to define code to be executed automatically
504 every time the user enters a new line.
505 A simple example would be to print the time of each command:
507 pdl> push @PERLDL::AUTO,'print scalar(gmtime),"\n"'
509 pdl> print zeroes(3,3)
511 Sun May 3 04:49:05 1998
512 [
514 [0 0 0]
515 [0 0 0]
516 [0 0 0]
517 ]
518 pdl> print "Boo"
520 Sun May 3 04:49:18 1998
521 Boo
522 pdl>
523 Or to make sure any changes in the file 'local.perldlrc' are always
525 picked up :-
526 pdl> push @PERLDL::AUTO,"do 'local.perldlrc'"
528 This code can of course be put *in* 'local.perldlrc', but be careful
530 :-) [Hint: add "unless ($started++)" to above to ensure it only gets
531 done once!]
532 Another example application is as a hook for Autoloaders (e.g.
534 PDL::AutoLoader) to add code too which allows them to automatically re-
535 scan their files for changes. This is extremely convenient at the
536 interactive command line. Since this hook is only in the shell it
537 imposes no inefficiency on PDL scripts.
538 Finally note this is a very powerful facility - which means it should
540 be used with caution!
541perl v5.38.0 2023-07-21 PERLDL(1)