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1 | =head1 NAME |
2 | ||
3 | perlapio - perl's IO abstraction interface. | |
4 | ||
5 | =head1 SYNOPSIS | |
6 | ||
7 | #define PERLIO_NOT_STDIO 0 /* For co-existence with stdio only */ | |
8 | #include <perlio.h> /* Usually via #include <perl.h> */ | |
9 | ||
10 | PerlIO *PerlIO_stdin(void); | |
11 | PerlIO *PerlIO_stdout(void); | |
12 | PerlIO *PerlIO_stderr(void); | |
13 | ||
14 | PerlIO *PerlIO_open(const char *path,const char *mode); | |
15 | PerlIO *PerlIO_fdopen(int fd, const char *mode); | |
16 | PerlIO *PerlIO_reopen(const char *path, const char *mode, PerlIO *old); /* deprecated */ | |
17 | int PerlIO_close(PerlIO *f); | |
18 | ||
19 | int PerlIO_stdoutf(const char *fmt,...) | |
20 | int PerlIO_puts(PerlIO *f,const char *string); | |
21 | int PerlIO_putc(PerlIO *f,int ch); | |
22 | int PerlIO_write(PerlIO *f,const void *buf,size_t numbytes); | |
23 | int PerlIO_printf(PerlIO *f, const char *fmt,...); | |
24 | int PerlIO_vprintf(PerlIO *f, const char *fmt, va_list args); | |
25 | int PerlIO_flush(PerlIO *f); | |
26 | ||
27 | int PerlIO_eof(PerlIO *f); | |
28 | int PerlIO_error(PerlIO *f); | |
29 | void PerlIO_clearerr(PerlIO *f); | |
30 | ||
31 | int PerlIO_getc(PerlIO *d); | |
32 | int PerlIO_ungetc(PerlIO *f,int ch); | |
33 | int PerlIO_read(PerlIO *f, void *buf, size_t numbytes); | |
34 | ||
35 | int PerlIO_fileno(PerlIO *f); | |
36 | ||
37 | void PerlIO_setlinebuf(PerlIO *f); | |
38 | ||
39 | Off_t PerlIO_tell(PerlIO *f); | |
40 | int PerlIO_seek(PerlIO *f, Off_t offset, int whence); | |
41 | void PerlIO_rewind(PerlIO *f); | |
42 | ||
43 | int PerlIO_getpos(PerlIO *f, SV *save); /* prototype changed */ | |
44 | int PerlIO_setpos(PerlIO *f, SV *saved); /* prototype changed */ | |
45 | ||
46 | int PerlIO_fast_gets(PerlIO *f); | |
47 | int PerlIO_has_cntptr(PerlIO *f); | |
48 | int PerlIO_get_cnt(PerlIO *f); | |
49 | char *PerlIO_get_ptr(PerlIO *f); | |
50 | void PerlIO_set_ptrcnt(PerlIO *f, char *ptr, int count); | |
51 | ||
52 | int PerlIO_canset_cnt(PerlIO *f); /* deprecated */ | |
53 | void PerlIO_set_cnt(PerlIO *f, int count); /* deprecated */ | |
54 | ||
55 | int PerlIO_has_base(PerlIO *f); | |
56 | char *PerlIO_get_base(PerlIO *f); | |
57 | int PerlIO_get_bufsiz(PerlIO *f); | |
58 | ||
59 | PerlIO *PerlIO_importFILE(FILE *stdio, const char *mode); | |
60 | FILE *PerlIO_exportFILE(PerlIO *f, int flags); | |
61 | FILE *PerlIO_findFILE(PerlIO *f); | |
62 | void PerlIO_releaseFILE(PerlIO *f,FILE *stdio); | |
63 | ||
64 | int PerlIO_apply_layers(PerlIO *f, const char *mode, const char *layers); | |
65 | int PerlIO_binmode(PerlIO *f, int ptype, int imode, const char *layers); | |
66 | void PerlIO_debug(const char *fmt,...) | |
67 | ||
68 | =head1 DESCRIPTION | |
69 | ||
70 | Perl's source code, and extensions that want maximum portability, | |
71 | should use the above functions instead of those defined in ANSI C's | |
72 | I<stdio.h>. The perl headers (in particular "perlio.h") will | |
73 | C<#define> them to the I/O mechanism selected at Configure time. | |
74 | ||
75 | The functions are modeled on those in I<stdio.h>, but parameter order | |
76 | has been "tidied up a little". | |
77 | ||
78 | C<PerlIO *> takes the place of FILE *. Like FILE * it should be | |
79 | treated as opaque (it is probably safe to assume it is a pointer to | |
80 | something). | |
81 | ||
82 | There are currently three implementations: | |
83 | ||
84 | =over 4 | |
85 | ||
86 | =item 1. USE_STDIO | |
87 | ||
88 | All above are #define'd to stdio functions or are trivial wrapper | |
89 | functions which call stdio. In this case I<only> PerlIO * is a FILE *. | |
90 | This has been the default implementation since the abstraction was | |
91 | introduced in perl5.003_02. | |
92 | ||
93 | =item 2. USE_SFIO | |
94 | ||
95 | A "legacy" implementation in terms of the "sfio" library. Used for | |
96 | some specialist applications on Unix machines ("sfio" is not widely | |
97 | ported away from Unix). Most of above are #define'd to the sfio | |
98 | functions. PerlIO * is in this case Sfio_t *. | |
99 | ||
100 | =item 3. USE_PERLIO | |
101 | ||
102 | Introduced just after perl5.7.0, this is a re-implementation of the | |
103 | above abstraction which allows perl more control over how IO is done | |
104 | as it decouples IO from the way the operating system and C library | |
105 | choose to do things. For USE_PERLIO PerlIO * has an extra layer of | |
106 | indirection - it is a pointer-to-a-pointer. This allows the PerlIO * | |
107 | to remain with a known value while swapping the implementation around | |
108 | underneath I<at run time>. In this case all the above are true (but | |
109 | very simple) functions which call the underlying implementation. | |
110 | ||
111 | This is the only implementation for which C<PerlIO_apply_layers()> | |
112 | does anything "interesting". | |
113 | ||
114 | The USE_PERLIO implementation is described in L<perliol>. | |
115 | ||
116 | =back | |
117 | ||
118 | Because "perlio.h" is a thin layer (for efficiency) the semantics of | |
119 | these functions are somewhat dependent on the underlying implementation. | |
120 | Where these variations are understood they are noted below. | |
121 | ||
122 | Unless otherwise noted, functions return 0 on success, or a negative | |
123 | value (usually C<EOF> which is usually -1) and set C<errno> on error. | |
124 | ||
125 | =over 4 | |
126 | ||
127 | =item B<PerlIO_stdin()>, B<PerlIO_stdout()>, B<PerlIO_stderr()> | |
128 | ||
129 | Use these rather than C<stdin>, C<stdout>, C<stderr>. They are written | |
130 | to look like "function calls" rather than variables because this makes | |
131 | it easier to I<make them> function calls if platform cannot export data | |
132 | to loaded modules, or if (say) different "threads" might have different | |
133 | values. | |
134 | ||
135 | =item B<PerlIO_open(path, mode)>, B<PerlIO_fdopen(fd,mode)> | |
136 | ||
137 | These correspond to fopen()/fdopen() and the arguments are the same. | |
138 | Return C<NULL> and set C<errno> if there is an error. There may be an | |
139 | implementation limit on the number of open handles, which may be lower | |
140 | than the limit on the number of open files - C<errno> may not be set | |
141 | when C<NULL> is returned if this limit is exceeded. | |
142 | ||
143 | =item B<PerlIO_reopen(path,mode,f)> | |
144 | ||
145 | While this currently exists in all three implementations perl itself | |
146 | does not use it. I<As perl does not use it, it is not well tested.> | |
147 | ||
148 | Perl prefers to C<dup> the new low-level descriptor to the descriptor | |
149 | used by the existing PerlIO. This may become the behaviour of this | |
150 | function in the future. | |
151 | ||
152 | =item B<PerlIO_printf(f,fmt,...)>, B<PerlIO_vprintf(f,fmt,a)> | |
153 | ||
154 | These are fprintf()/vfprintf() equivalents. | |
155 | ||
156 | =item B<PerlIO_stdoutf(fmt,...)> | |
157 | ||
158 | This is printf() equivalent. printf is #defined to this function, | |
159 | so it is (currently) legal to use C<printf(fmt,...)> in perl sources. | |
160 | ||
161 | =item B<PerlIO_read(f,buf,count)>, B<PerlIO_write(f,buf,count)> | |
162 | ||
163 | These correspond functionally to fread() and fwrite() but the | |
164 | arguments and return values are different. The PerlIO_read() and | |
165 | PerlIO_write() signatures have been modeled on the more sane low level | |
166 | read() and write() functions instead: The "file" argument is passed | |
167 | first, there is only one "count", and the return value can distinguish | |
168 | between error and C<EOF>. | |
169 | ||
170 | Returns a byte count if successful (which may be zero or | |
171 | positive), returns negative value and sets C<errno> on error. | |
172 | Depending on implementation C<errno> may be C<EINTR> if operation was | |
173 | interrupted by a signal. | |
174 | ||
175 | =item B<PerlIO_close(f)> | |
176 | ||
177 | Depending on implementation C<errno> may be C<EINTR> if operation was | |
178 | interrupted by a signal. | |
179 | ||
180 | =item B<PerlIO_puts(f,s)>, B<PerlIO_putc(f,c)> | |
181 | ||
182 | These correspond to fputs() and fputc(). | |
183 | Note that arguments have been revised to have "file" first. | |
184 | ||
185 | =item B<PerlIO_ungetc(f,c)> | |
186 | ||
187 | This corresponds to ungetc(). Note that arguments have been revised | |
188 | to have "file" first. Arranges that next read operation will return | |
189 | the byte B<c>. Despite the implied "character" in the name only | |
190 | values in the range 0..0xFF are defined. Returns the byte B<c> on | |
191 | success or -1 (C<EOF>) on error. The number of bytes that can be | |
192 | "pushed back" may vary, only 1 character is certain, and then only if | |
193 | it is the last character that was read from the handle. | |
194 | ||
195 | =item B<PerlIO_getc(f)> | |
196 | ||
197 | This corresponds to getc(). | |
198 | Despite the c in the name only byte range 0..0xFF is supported. | |
199 | Returns the character read or -1 (C<EOF>) on error. | |
200 | ||
201 | =item B<PerlIO_eof(f)> | |
202 | ||
203 | This corresponds to feof(). Returns a true/false indication of | |
204 | whether the handle is at end of file. For terminal devices this may | |
205 | or may not be "sticky" depending on the implementation. The flag is | |
206 | cleared by PerlIO_seek(), or PerlIO_rewind(). | |
207 | ||
208 | =item B<PerlIO_error(f)> | |
209 | ||
210 | This corresponds to ferror(). Returns a true/false indication of | |
211 | whether there has been an IO error on the handle. | |
212 | ||
213 | =item B<PerlIO_fileno(f)> | |
214 | ||
215 | This corresponds to fileno(), note that on some platforms, the meaning | |
216 | of "fileno" may not match Unix. Returns -1 if the handle has no open | |
217 | descriptor associated with it. | |
218 | ||
219 | =item B<PerlIO_clearerr(f)> | |
220 | ||
221 | This corresponds to clearerr(), i.e., clears 'error' and (usually) | |
222 | 'eof' flags for the "stream". Does not return a value. | |
223 | ||
224 | =item B<PerlIO_flush(f)> | |
225 | ||
226 | This corresponds to fflush(). Sends any buffered write data to the | |
227 | underlying file. If called with C<NULL> this may flush all open | |
228 | streams (or core dump with some USE_STDIO implementations). Calling | |
229 | on a handle open for read only, or on which last operation was a read | |
230 | of some kind may lead to undefined behaviour on some USE_STDIO | |
231 | implementations. The USE_PERLIO (layers) implementation tries to | |
232 | behave better: it flushes all open streams when passed C<NULL>, and | |
233 | attempts to retain data on read streams either in the buffer or by | |
234 | seeking the handle to the current logical position. | |
235 | ||
236 | =item B<PerlIO_seek(f,offset,whence)> | |
237 | ||
238 | This corresponds to fseek(). Sends buffered write data to the | |
239 | underlying file, or discards any buffered read data, then positions | |
240 | the file descriptor as specified by B<offset> and B<whence> (sic). | |
241 | This is the correct thing to do when switching between read and write | |
242 | on the same handle (see issues with PerlIO_flush() above). Offset is | |
243 | of type C<Off_t> which is a perl Configure value which may not be same | |
244 | as stdio's C<off_t>. | |
245 | ||
246 | =item B<PerlIO_tell(f)> | |
247 | ||
248 | This corresponds to ftell(). Returns the current file position, or | |
249 | (Off_t) -1 on error. May just return value system "knows" without | |
250 | making a system call or checking the underlying file descriptor (so | |
251 | use on shared file descriptors is not safe without a | |
252 | PerlIO_seek()). Return value is of type C<Off_t> which is a perl | |
253 | Configure value which may not be same as stdio's C<off_t>. | |
254 | ||
255 | =item B<PerlIO_getpos(f,p)>, B<PerlIO_setpos(f,p)> | |
256 | ||
257 | These correspond (loosely) to fgetpos() and fsetpos(). Rather than | |
258 | stdio's Fpos_t they expect a "Perl Scalar Value" to be passed. What is | |
259 | stored there should be considered opaque. The layout of the data may | |
260 | vary from handle to handle. When not using stdio or if platform does | |
261 | not have the stdio calls then they are implemented in terms of | |
262 | PerlIO_tell() and PerlIO_seek(). | |
263 | ||
264 | =item B<PerlIO_rewind(f)> | |
265 | ||
266 | This corresponds to rewind(). It is usually defined as being | |
267 | ||
268 | PerlIO_seek(f,(Off_t)0L, SEEK_SET); | |
269 | PerlIO_clearerr(f); | |
270 | ||
271 | =item B<PerlIO_tmpfile()> | |
272 | ||
273 | This corresponds to tmpfile(), i.e., returns an anonymous PerlIO or | |
274 | NULL on error. The system will attempt to automatically delete the | |
275 | file when closed. On Unix the file is usually C<unlink>-ed just after | |
276 | it is created so it does not matter how it gets closed. On other | |
277 | systems the file may only be deleted if closed via PerlIO_close() | |
278 | and/or the program exits via C<exit>. Depending on the implementation | |
279 | there may be "race conditions" which allow other processes access to | |
280 | the file, though in general it will be safer in this regard than | |
281 | ad. hoc. schemes. | |
282 | ||
283 | =item B<PerlIO_setlinebuf(f)> | |
284 | ||
285 | This corresponds to setlinebuf(). Does not return a value. What | |
286 | constitutes a "line" is implementation dependent but usually means | |
287 | that writing "\n" flushes the buffer. What happens with things like | |
288 | "this\nthat" is uncertain. (Perl core uses it I<only> when "dumping"; | |
289 | it has nothing to do with $| auto-flush.) | |
290 | ||
291 | =back | |
292 | ||
293 | =head2 Co-existence with stdio | |
294 | ||
295 | There is outline support for co-existence of PerlIO with stdio. | |
296 | Obviously if PerlIO is implemented in terms of stdio there is no | |
297 | problem. However in other cases then mechanisms must exist to create a | |
298 | FILE * which can be passed to library code which is going to use stdio | |
299 | calls. | |
300 | ||
301 | The first step is to add this line: | |
302 | ||
303 | #define PERLIO_NOT_STDIO 0 | |
304 | ||
305 | I<before> including any perl header files. (This will probably become | |
306 | the default at some point). That prevents "perlio.h" from attempting | |
307 | to #define stdio functions onto PerlIO functions. | |
308 | ||
309 | XS code is probably better using "typemap" if it expects FILE * | |
310 | arguments. The standard typemap will be adjusted to comprehend any | |
311 | changes in this area. | |
312 | ||
313 | =over 4 | |
314 | ||
315 | =item B<PerlIO_importFILE(f,mode)> | |
316 | ||
317 | Used to get a PerlIO * from a FILE *. | |
318 | ||
319 | The mode argument should be a string as would be passed to | |
320 | fopen/PerlIO_open. If it is NULL then - for legacy support - the code | |
321 | will (depending upon the platform and the implementation) either | |
322 | attempt to empirically determine the mode in which I<f> is open, or | |
323 | use "r+" to indicate a read/write stream. | |
324 | ||
325 | Once called the FILE * should I<ONLY> be closed by calling | |
326 | C<PerlIO_close()> on the returned PerlIO *. | |
327 | ||
328 | The PerlIO is set to textmode. Use PerlIO_binmode if this is | |
329 | not the desired mode. | |
330 | ||
331 | This is B<not> the reverse of PerlIO_exportFILE(). | |
332 | ||
333 | =item B<PerlIO_exportFILE(f,mode)> | |
334 | ||
335 | Given a PerlIO * create a 'native' FILE * suitable for passing to code | |
336 | expecting to be compiled and linked with ANSI C I<stdio.h>. The mode | |
337 | argument should be a string as would be passed to fopen/PerlIO_open. | |
338 | If it is NULL then - for legacy support - the FILE * is opened in same | |
339 | mode as the PerlIO *. | |
340 | ||
341 | The fact that such a FILE * has been 'exported' is recorded, (normally | |
342 | by pushing a new :stdio "layer" onto the PerlIO *), which may affect | |
343 | future PerlIO operations on the original PerlIO *. You should not | |
344 | call C<fclose()> on the file unless you call C<PerlIO_releaseFILE()> | |
345 | to disassociate it from the PerlIO *. (Do not use PerlIO_importFILE() | |
346 | for doing the disassociation.) | |
347 | ||
348 | Calling this function repeatedly will create a FILE * on each call | |
349 | (and will push an :stdio layer each time as well). | |
350 | ||
351 | =item B<PerlIO_releaseFILE(p,f)> | |
352 | ||
353 | Calling PerlIO_releaseFILE informs PerlIO that all use of FILE * is | |
354 | complete. It is removed from the list of 'exported' FILE *s, and the | |
355 | associated PerlIO * should revert to its original behaviour. | |
356 | ||
357 | Use this to disassociate a file from a PerlIO * that was associated | |
358 | using PerlIO_exportFILE(). | |
359 | ||
360 | =item B<PerlIO_findFILE(f)> | |
361 | ||
362 | Returns a native FILE * used by a stdio layer. If there is none, it | |
363 | will create one with PerlIO_exportFILE. In either case the FILE * | |
364 | should be considered as belonging to PerlIO subsystem and should | |
365 | only be closed by calling C<PerlIO_close()>. | |
366 | ||
367 | ||
368 | =back | |
369 | ||
370 | =head2 "Fast gets" Functions | |
371 | ||
372 | In addition to standard-like API defined so far above there is an | |
373 | "implementation" interface which allows perl to get at internals of | |
374 | PerlIO. The following calls correspond to the various FILE_xxx macros | |
375 | determined by Configure - or their equivalent in other | |
376 | implementations. This section is really of interest to only those | |
377 | concerned with detailed perl-core behaviour, implementing a PerlIO | |
378 | mapping or writing code which can make use of the "read ahead" that | |
379 | has been done by the IO system in the same way perl does. Note that | |
380 | any code that uses these interfaces must be prepared to do things the | |
381 | traditional way if a handle does not support them. | |
382 | ||
383 | =over 4 | |
384 | ||
385 | =item B<PerlIO_fast_gets(f)> | |
386 | ||
387 | Returns true if implementation has all the interfaces required to | |
388 | allow perl's C<sv_gets> to "bypass" normal IO mechanism. This can | |
389 | vary from handle to handle. | |
390 | ||
391 | PerlIO_fast_gets(f) = PerlIO_has_cntptr(f) && \ | |
392 | PerlIO_canset_cnt(f) && \ | |
393 | `Can set pointer into buffer' | |
394 | ||
395 | ||
396 | =item B<PerlIO_has_cntptr(f)> | |
397 | ||
398 | Implementation can return pointer to current position in the "buffer" | |
399 | and a count of bytes available in the buffer. Do not use this - use | |
400 | PerlIO_fast_gets. | |
401 | ||
402 | =item B<PerlIO_get_cnt(f)> | |
403 | ||
404 | Return count of readable bytes in the buffer. Zero or negative return | |
405 | means no more bytes available. | |
406 | ||
407 | =item B<PerlIO_get_ptr(f)> | |
408 | ||
409 | Return pointer to next readable byte in buffer, accessing via the | |
410 | pointer (dereferencing) is only safe if PerlIO_get_cnt() has returned | |
411 | a positive value. Only positive offsets up to value returned by | |
412 | PerlIO_get_cnt() are allowed. | |
413 | ||
414 | =item B<PerlIO_set_ptrcnt(f,p,c)> | |
415 | ||
416 | Set pointer into buffer, and a count of bytes still in the | |
417 | buffer. Should be used only to set pointer to within range implied by | |
418 | previous calls to C<PerlIO_get_ptr> and C<PerlIO_get_cnt>. The two | |
419 | values I<must> be consistent with each other (implementation may only | |
420 | use one or the other or may require both). | |
421 | ||
422 | =item B<PerlIO_canset_cnt(f)> | |
423 | ||
424 | Implementation can adjust its idea of number of bytes in the buffer. | |
425 | Do not use this - use PerlIO_fast_gets. | |
426 | ||
427 | =item B<PerlIO_set_cnt(f,c)> | |
428 | ||
429 | Obscure - set count of bytes in the buffer. Deprecated. Only usable | |
430 | if PerlIO_canset_cnt() returns true. Currently used in only doio.c to | |
431 | force count less than -1 to -1. Perhaps should be PerlIO_set_empty or | |
432 | similar. This call may actually do nothing if "count" is deduced from | |
433 | pointer and a "limit". Do not use this - use PerlIO_set_ptrcnt(). | |
434 | ||
435 | =item B<PerlIO_has_base(f)> | |
436 | ||
437 | Returns true if implementation has a buffer, and can return pointer | |
438 | to whole buffer and its size. Used by perl for B<-T> / B<-B> tests. | |
439 | Other uses would be very obscure... | |
440 | ||
441 | =item B<PerlIO_get_base(f)> | |
442 | ||
443 | Return I<start> of buffer. Access only positive offsets in the buffer | |
444 | up to the value returned by PerlIO_get_bufsiz(). | |
445 | ||
446 | =item B<PerlIO_get_bufsiz(f)> | |
447 | ||
448 | Return the I<total number of bytes> in the buffer, this is neither the | |
449 | number that can be read, nor the amount of memory allocated to the | |
450 | buffer. Rather it is what the operating system and/or implementation | |
451 | happened to C<read()> (or whatever) last time IO was requested. | |
452 | ||
453 | =back | |
454 | ||
455 | =head2 Other Functions | |
456 | ||
457 | =over 4 | |
458 | ||
459 | =item PerlIO_apply_layers(f,mode,layers) | |
460 | ||
461 | The new interface to the USE_PERLIO implementation. The layers ":crlf" | |
462 | and ":raw" are only ones allowed for other implementations and those | |
463 | are silently ignored. (As of perl5.8 ":raw" is deprecated.) Use | |
464 | PerlIO_binmode() below for the portable case. | |
465 | ||
466 | =item PerlIO_binmode(f,ptype,imode,layers) | |
467 | ||
468 | The hook used by perl's C<binmode> operator. | |
469 | B<ptype> is perl's character for the kind of IO: | |
470 | ||
471 | =over 8 | |
472 | ||
473 | =item 'E<lt>' read | |
474 | ||
475 | =item 'E<gt>' write | |
476 | ||
477 | =item '+' read/write | |
478 | ||
479 | =back | |
480 | ||
481 | B<imode> is C<O_BINARY> or C<O_TEXT>. | |
482 | ||
483 | B<layers> is a string of layers to apply, only ":crlf" makes sense in | |
484 | the non USE_PERLIO case. (As of perl5.8 ":raw" is deprecated in favour | |
485 | of passing NULL.) | |
486 | ||
487 | Portable cases are: | |
488 | ||
489 | PerlIO_binmode(f,ptype,O_BINARY,Nullch); | |
490 | and | |
491 | PerlIO_binmode(f,ptype,O_TEXT,":crlf"); | |
492 | ||
493 | On Unix these calls probably have no effect whatsoever. Elsewhere | |
494 | they alter "\n" to CR,LF translation and possibly cause a special text | |
495 | "end of file" indicator to be written or honoured on read. The effect | |
496 | of making the call after doing any IO to the handle depends on the | |
497 | implementation. (It may be ignored, affect any data which is already | |
498 | buffered as well, or only apply to subsequent data.) | |
499 | ||
500 | =item PerlIO_debug(fmt,...) | |
501 | ||
502 | PerlIO_debug is a printf()-like function which can be used for | |
503 | debugging. No return value. Its main use is inside PerlIO where using | |
504 | real printf, warn() etc. would recursively call PerlIO and be a | |
505 | problem. | |
506 | ||
507 | PerlIO_debug writes to the file named by $ENV{'PERLIO_DEBUG'} typical | |
508 | use might be | |
509 | ||
510 | Bourne shells (sh, ksh, bash, zsh, ash, ...): | |
511 | PERLIO_DEBUG=/dev/tty ./perl somescript some args | |
512 | ||
513 | Csh/Tcsh: | |
514 | setenv PERLIO_DEBUG /dev/tty | |
515 | ./perl somescript some args | |
516 | ||
517 | If you have the "env" utility: | |
518 | env PERLIO_DEBUG=/dev/tty ./perl somescript some args | |
519 | ||
520 | Win32: | |
521 | set PERLIO_DEBUG=CON | |
522 | perl somescript some args | |
523 | ||
524 | If $ENV{'PERLIO_DEBUG'} is not set PerlIO_debug() is a no-op. | |
525 | ||
526 | =back |