Commit | Line | Data |
760ac839 |
1 | =head1 NAME |
2 | |
28757baa |
3 | perlapio - perl's IO abstraction interface. |
760ac839 |
4 | |
5 | =head1 SYNOPSIS |
6 | |
3039a93d |
7 | #define PERLIO_NOT_STDIO 0 /* For co-existence with stdio only */ |
50b80e25 |
8 | #include <perlio.h> /* Usually via #include <perl.h> */ |
9 | |
760ac839 |
10 | PerlIO *PerlIO_stdin(void); |
11 | PerlIO *PerlIO_stdout(void); |
12 | PerlIO *PerlIO_stderr(void); |
54310121 |
13 | |
50b80e25 |
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, int flags); |
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,...) |
760ac839 |
67 | |
68 | =head1 DESCRIPTION |
69 | |
50b80e25 |
70 | Perl's source code, and extensions that want maximum portability, should use the above |
71 | functions instead of those defined in ANSI C's I<stdio.h>. The perl headers (in |
72 | particular "perlio.h") will C<#define> them to the I/O mechanism selected at Configure time. |
760ac839 |
73 | |
74 | The functions are modeled on those in I<stdio.h>, but parameter order |
75 | has been "tidied up a little". |
76 | |
50b80e25 |
77 | C<PerlIO *> takes the place of FILE *. Like FILE * it should be treated as |
78 | opaque (it is probably safe to assume it is a pointer to something). |
79 | |
80 | There are currently three implementations: |
81 | |
760ac839 |
82 | =over 4 |
83 | |
50b80e25 |
84 | =item 1. USE_STDIO |
760ac839 |
85 | |
50b80e25 |
86 | All above are #define'd to stdio functions or are trivial wrapper functions which |
87 | call stdio. In this case I<only> PerlIO * is a FILE *. |
88 | This has been the default implementation since the abstraction was introduced |
89 | in perl5.003_02. |
90 | |
91 | =item 2. USE_SFIO |
92 | |
93 | A "legacy" implementation in terms of the "sfio" library. Used for some specialist |
94 | applications on Unix machines ("sfio" is not widely ported away from Unix). |
95 | Most of above are #define'd to the sfio functions. PerlIO * is in this case Sfio_t *. |
96 | |
97 | =item 3. USE_PERLIO |
98 | |
99 | Introduced just after perl5.7.0 this is a re-implementation of the above abstraction |
100 | which allows perl more control over how IO is done as it decouples IO from the |
101 | way the operating system and C library choose to do things. For USE_PERLIO |
102 | PerlIO * has an extra layer of indirection - it is a pointer-to-a-pointer. |
103 | This allows the PerlIO * to remain with a known value while swapping the |
104 | implementation arround underneath I<at run time>. In this case all the |
105 | above are true (but very simple) functions which call the underlying implementation. |
106 | |
107 | This is the only implementation for which C<PerlIO_apply_layers()> does anything |
108 | "interesting". |
109 | |
110 | The USE_PERLIO implementation is described in L<perliol>. |
111 | |
112 | =back |
113 | |
114 | Because "perlio.h" is a thing layer (for efficiency) the semantics of these functions are |
3039a93d |
115 | somewhat dependent on the the underlying implementation. Where these variations are |
50b80e25 |
116 | understood they are noted below. |
117 | |
3039a93d |
118 | Unless otherwise noted, functions return 0 on success, or a negative value (usually |
50b80e25 |
119 | C<EOF> which is usually -1) and set C<errno> on error. |
120 | |
121 | =over 4 |
760ac839 |
122 | |
123 | =item B<PerlIO_stdin()>, B<PerlIO_stdout()>, B<PerlIO_stderr()> |
124 | |
125 | Use these rather than C<stdin>, C<stdout>, C<stderr>. They are written |
126 | to look like "function calls" rather than variables because this makes |
54310121 |
127 | it easier to I<make them> function calls if platform cannot export data |
128 | to loaded modules, or if (say) different "threads" might have different |
760ac839 |
129 | values. |
130 | |
131 | =item B<PerlIO_open(path, mode)>, B<PerlIO_fdopen(fd,mode)> |
132 | |
3039a93d |
133 | These correspond to fopen()/fdopen() and the arguments are the same. |
134 | Return C<NULL> and set C<errno> if there is an error. |
135 | There may be an implementation limit on the number of open handles, which may |
50b80e25 |
136 | be lower than the limit on the number of open files - C<errno> may |
3039a93d |
137 | not be set when C<NULL> is returned if this limnit is exceeded. |
50b80e25 |
138 | |
11e1c8f2 |
139 | =item B<PerlIO_reopen(path,mode,f)> |
50b80e25 |
140 | |
141 | While this currently exists in all three implementations perl itself |
142 | does not use it. I<As perl does not use it, it is not well tested.> |
143 | |
144 | Perl prefers to C<dup> the new low-level descriptor to the descriptor used |
145 | by the existing PerlIO. This may become the behaviour of this function |
146 | in the future. |
760ac839 |
147 | |
148 | =item B<PerlIO_printf(f,fmt,...)>, B<PerlIO_vprintf(f,fmt,a)> |
149 | |
7b8d334a |
150 | These are fprintf()/vfprintf() equivalents. |
760ac839 |
151 | |
152 | =item B<PerlIO_stdoutf(fmt,...)> |
153 | |
154 | This is printf() equivalent. printf is #defined to this function, |
84dc3c4d |
155 | so it is (currently) legal to use C<printf(fmt,...)> in perl sources. |
760ac839 |
156 | |
157 | =item B<PerlIO_read(f,buf,count)>, B<PerlIO_write(f,buf,count)> |
158 | |
54310121 |
159 | These correspond to fread() and fwrite(). Note that arguments |
760ac839 |
160 | are different, there is only one "count" and order has |
50b80e25 |
161 | "file" first. Returns a byte count if successful (which may be zero), |
162 | returns negative value and sets C<errno> on error. |
163 | Depending on implementation C<errno> may be C<EINTR> if operation |
164 | was interrupted by a signal. |
760ac839 |
165 | |
166 | =item B<PerlIO_close(f)> |
167 | |
50b80e25 |
168 | Depending on implementation C<errno> may be C<EINTR> if operation |
169 | was interrupted by a signal. |
170 | |
21917246 |
171 | =item B<PerlIO_puts(f,s)>, B<PerlIO_putc(f,c)> |
760ac839 |
172 | |
54310121 |
173 | These correspond to fputs() and fputc(). |
760ac839 |
174 | Note that arguments have been revised to have "file" first. |
175 | |
21917246 |
176 | =item B<PerlIO_ungetc(f,c)> |
760ac839 |
177 | |
178 | This corresponds to ungetc(). |
179 | Note that arguments have been revised to have "file" first. |
50b80e25 |
180 | Arranges that next read operation will return the byte B<c>. |
181 | Despite the implied "character" in the name only values in the |
182 | range 0..0xFF are defined. Returns the byte B<c> on success or -1 (C<EOF>) on error. |
183 | The number of bytes that can be "pushed back" may vary, only 1 character is |
184 | certain, and then only if it is the last character that was read from the handle. |
760ac839 |
185 | |
186 | =item B<PerlIO_getc(f)> |
187 | |
188 | This corresponds to getc(). |
50b80e25 |
189 | Despite the c in the name only byte range 0..0xFF is supported. |
3039a93d |
190 | Returns the character read or -1 (C<EOF>) on error. |
760ac839 |
191 | |
192 | =item B<PerlIO_eof(f)> |
193 | |
194 | This corresponds to feof(). |
50b80e25 |
195 | Returns a true/false indication of whether the handle is at end of file. |
196 | For terminal devices this may or may not be "sticky" depending on the implementation. |
197 | The flag is cleared by PerlIO_seek(), or PerlIO_rewind(). |
760ac839 |
198 | |
199 | =item B<PerlIO_error(f)> |
200 | |
201 | This corresponds to ferror(). |
50b80e25 |
202 | Returns a true/false indication of whether there has been an IO error on the handle. |
760ac839 |
203 | |
204 | =item B<PerlIO_fileno(f)> |
205 | |
54310121 |
206 | This corresponds to fileno(), note that on some platforms, |
3039a93d |
207 | the meaning of "fileno" may not match Unix. Returns -1 if the handle has no |
50b80e25 |
208 | open descriptor associated with it. |
760ac839 |
209 | |
210 | =item B<PerlIO_clearerr(f)> |
211 | |
50b80e25 |
212 | This corresponds to clearerr(), i.e., clears 'error' and (usually) 'eof' |
213 | flags for the "stream". Does not return a value. |
760ac839 |
214 | |
215 | =item B<PerlIO_flush(f)> |
216 | |
217 | This corresponds to fflush(). |
50b80e25 |
218 | Sends any buffered write data to the underlying file. |
219 | If called with C<NULL> this may flush all open streams (or core dump). |
220 | Calling on a handle open for read only, or on which last operation was a read of some kind |
221 | may lead to undefined behaviour. |
760ac839 |
222 | |
50b80e25 |
223 | =item B<PerlIO_seek(f,offset,whence)> |
760ac839 |
224 | |
50b80e25 |
225 | This corresponds to fseek(). |
226 | Sends buffered write data to the underlying file, or discards any buffered |
227 | read data, then positions the file desciptor as specified by B<offset> and B<whence> (sic). |
228 | This is the correct thing to do when switching between read and write on the same |
229 | handle (see issues with PerlIO_flush() above). |
230 | Offset is of type C<Off_t> which is a perl Configure value which may not be same |
231 | as stdio's C<off_t>. |
760ac839 |
232 | |
50b80e25 |
233 | =item B<PerlIO_tell(f)> |
760ac839 |
234 | |
50b80e25 |
235 | This corresponds to ftell(). |
236 | Returns the current file position, or (Off_t) -1 on error. |
237 | May just return value system "knows" without making a system call or checking |
3039a93d |
238 | the underlying file descriptor (so use on shared file descriptors is not |
50b80e25 |
239 | safe without a PerlIO_seek()). Return value is of type C<Off_t> which is a perl Configure |
240 | value which may not be same as stdio's C<off_t>. |
760ac839 |
241 | |
242 | =item B<PerlIO_getpos(f,p)>, B<PerlIO_setpos(f,p)> |
243 | |
50b80e25 |
244 | These correspond (loosely) to fgetpos() and fsetpos(). Rather than stdio's Fpos_t |
245 | they expect a "Perl Scalar Value" to be passed. What is stored there should |
3039a93d |
246 | be considered opaque. The layout of the data may vary from handle to handle. |
50b80e25 |
247 | When not using stdio or if platform does not have the stdio calls then they are |
248 | implemented in terms of PerlIO_tell() and PerlIO_seek(). |
760ac839 |
249 | |
250 | =item B<PerlIO_rewind(f)> |
251 | |
50b80e25 |
252 | This corresponds to rewind(). It is usually defined as being |
253 | |
254 | PerlIO_seek(f,(Off_t)0L, SEEK_SET); |
255 | PerlIO_clearerr(f); |
256 | |
760ac839 |
257 | |
258 | =item B<PerlIO_tmpfile()> |
259 | |
5f05dabc |
260 | This corresponds to tmpfile(), i.e., returns an anonymous |
50b80e25 |
261 | PerlIO or NULL on error. |
3039a93d |
262 | The system will attempt to automatically delete the file when closed. |
50b80e25 |
263 | On Unix the file is usually C<unlink>-ed just after |
264 | it is created so it does not matter how it gets closed. On other systems the file may |
265 | only be deleted if closed via PerlIO_close() and/or the program exits via C<exit>. |
266 | Depending on the implementation there may be "race conditions" which allow other |
267 | processes access to the file, though in general it will be safer in this regard |
268 | than ad. hoc. schemes. |
269 | |
270 | =item B<PerlIO_setlinebuf(f)> |
271 | |
272 | This corresponds to setlinebuf(). |
273 | Does not return a value. What constitutes a "line" is implementation |
3039a93d |
274 | dependent but usually means that writing "\n" flushes the buffer. |
50b80e25 |
275 | What happens with things like "this\nthat" is uncertain. |
276 | (Perl core uses it I<only> when "dumping"; it has nothing to do with $| auto-flush.) |
760ac839 |
277 | |
54310121 |
278 | =back |
760ac839 |
279 | |
510d21e9 |
280 | =head2 Co-existence with stdio |
760ac839 |
281 | |
510d21e9 |
282 | There is outline support for co-existence of PerlIO with stdio. |
54310121 |
283 | Obviously if PerlIO is implemented in terms of stdio there is |
50b80e25 |
284 | no problem. However in other cases then mechanisms must exist to create a FILE * |
285 | which can be passed to library code which is going to use stdio calls. |
286 | |
287 | The fisrt step is to add this line: |
288 | |
289 | #define PERLIO_NOT_STDIO 0 |
290 | |
291 | I<before> including any perl header files. (This will probably become the |
292 | default at some point). That prevents "perlio.h" from attempting to |
293 | #define stdio functions onto PerlIO functions. |
294 | |
295 | XS code is probably better using "typemap" if it expects FILE * arguments. |
3039a93d |
296 | The standard typemap will be adjusted to comprehend any changes in this area. |
760ac839 |
297 | |
298 | =over 4 |
299 | |
300 | =item B<PerlIO_importFILE(f,flags)> |
301 | |
302 | Used to get a PerlIO * from a FILE *. |
303 | May need additional arguments, interface under review. |
304 | |
50b80e25 |
305 | The flags argument was meant to be used for read vs write vs read/write |
306 | information. In hindsight it would have been better to make it a char *mode |
307 | as in fopen/freopen. |
308 | |
760ac839 |
309 | =item B<PerlIO_exportFILE(f,flags)> |
310 | |
3039a93d |
311 | Given a PerlIO * return a 'native' FILE * suitable for |
54310121 |
312 | passing to code expecting to be compiled and linked with |
760ac839 |
313 | ANSI C I<stdio.h>. |
314 | |
315 | The fact that such a FILE * has been 'exported' is recorded, |
54310121 |
316 | and may affect future PerlIO operations on the original |
317 | PerlIO *. |
760ac839 |
318 | |
319 | =item B<PerlIO_findFILE(f)> |
320 | |
321 | Returns previously 'exported' FILE * (if any). |
322 | Place holder until interface is fully defined. |
323 | |
324 | =item B<PerlIO_releaseFILE(p,f)> |
325 | |
326 | Calling PerlIO_releaseFILE informs PerlIO that all use |
327 | of FILE * is complete. It is removed from list of 'exported' |
54310121 |
328 | FILE *s, and associated PerlIO * should revert to original |
760ac839 |
329 | behaviour. |
330 | |
760ac839 |
331 | =back |
332 | |
50b80e25 |
333 | =head2 "Fast gets" Functions |
334 | |
335 | In addition to standard-like API defined so far above there is an "implementation" interface |
760ac839 |
336 | which allows perl to get at internals of PerlIO. |
337 | The following calls correspond to the various FILE_xxx macros determined |
50b80e25 |
338 | by Configure - or their equivalent in other implementations. This section is really of |
339 | interest to only those concerned with detailed perl-core behaviour, implementing a |
340 | PerlIO mapping or writing code which can make use of the "read ahead" that has been done by |
341 | the IO system in the same way perl does. Note that any code that uses these interfaces |
342 | must be prepared to do things the traditional way if a handle does not support |
343 | them. |
760ac839 |
344 | |
345 | =over 4 |
346 | |
50b80e25 |
347 | =item B<PerlIO_fast_gets(f)> |
760ac839 |
348 | |
50b80e25 |
349 | Returns true if implementation has all the interfaces required to |
350 | allow perl's C<sv_gets> to "bypass" normal IO mechanism. |
351 | This can vary from handle to handle. |
760ac839 |
352 | |
50b80e25 |
353 | PerlIO_fast_gets(f) = PerlIO_has_cntptr(f) && \ |
354 | PerlIO_canset_cnt(f) && \ |
355 | `Can set pointer into buffer' |
760ac839 |
356 | |
760ac839 |
357 | |
50b80e25 |
358 | =item B<PerlIO_has_cntptr(f)> |
760ac839 |
359 | |
50b80e25 |
360 | Implementation can return pointer to current position in the "buffer" and |
361 | a count of bytes available in the buffer. |
362 | Do not use this - use PerlIO_fast_gets. |
760ac839 |
363 | |
50b80e25 |
364 | =item B<PerlIO_get_cnt(f)> |
760ac839 |
365 | |
50b80e25 |
366 | Return count of readable bytes in the buffer. Zero or negative return means |
367 | no more bytes available. |
760ac839 |
368 | |
50b80e25 |
369 | =item B<PerlIO_get_ptr(f)> |
760ac839 |
370 | |
50b80e25 |
371 | Return pointer to next readable byte in buffer, accessing via the pointer |
372 | (dereferencing) is only safe if PerlIO_get_cnt() has returned a positive value. |
373 | Only positive offsets up to value returned by PerlIO_get_cnt() are allowed. |
760ac839 |
374 | |
375 | =item B<PerlIO_set_ptrcnt(f,p,c)> |
376 | |
54310121 |
377 | Set pointer into buffer, and a count of bytes still in the |
5f05dabc |
378 | buffer. Should be used only to set |
760ac839 |
379 | pointer to within range implied by previous calls |
50b80e25 |
380 | to C<PerlIO_get_ptr> and C<PerlIO_get_cnt>. The two values I<must> be consistent |
3039a93d |
381 | with each other (implementation may only use one or the other or may require both). |
50b80e25 |
382 | |
383 | =item B<PerlIO_canset_cnt(f)> |
384 | |
385 | Implementation can adjust its idea of number of bytes in the buffer. |
386 | Do not use this - use PerlIO_fast_gets. |
760ac839 |
387 | |
388 | =item B<PerlIO_set_cnt(f,c)> |
389 | |
390 | Obscure - set count of bytes in the buffer. Deprecated. |
50b80e25 |
391 | Only usable if PerlIO_canset_cnt() returns true. |
11e1c8f2 |
392 | Currently used in only doio.c to force count less than -1 to -1. |
760ac839 |
393 | Perhaps should be PerlIO_set_empty or similar. |
394 | This call may actually do nothing if "count" is deduced from pointer |
54310121 |
395 | and a "limit". |
50b80e25 |
396 | Do not use this - use PerlIO_set_ptrcnt(). |
760ac839 |
397 | |
398 | =item B<PerlIO_has_base(f)> |
399 | |
50b80e25 |
400 | Returns true if implementation has a buffer, and can return pointer |
760ac839 |
401 | to whole buffer and its size. Used by perl for B<-T> / B<-B> tests. |
402 | Other uses would be very obscure... |
403 | |
404 | =item B<PerlIO_get_base(f)> |
405 | |
50b80e25 |
406 | Return I<start> of buffer. Access only positive offsets in the buffer |
407 | up to the value returned by PerlIO_get_bufsiz(). |
760ac839 |
408 | |
409 | =item B<PerlIO_get_bufsiz(f)> |
410 | |
50b80e25 |
411 | Return the I<total number of bytes> in the buffer, this is neither the number |
412 | that can be read, nor the amount of memory allocated to the buffer. Rather |
413 | it is what the operating system and/or implementation happened to C<read()> |
414 | (or whatever) last time IO was requested. |
415 | |
416 | =back |
417 | |
418 | =head2 Other Functions |
419 | |
420 | =over 4 |
421 | |
422 | =item PerlIO_apply_layers(f,mode,layers) |
423 | |
424 | The new interface to the USE_PERLIO implementation. The layers ":crlf" |
425 | and ":raw" are only ones allowed for other implementations and those |
426 | are silently ignored. Use PerlIO_binmode() below for the portable |
427 | case. |
428 | |
429 | =item PerlIO_binmode(f,ptype,imode,layers) |
430 | |
431 | The hook used by perl's C<binmode> operator. |
432 | B<ptype> is perl's charcter for the kind of IO: |
433 | |
434 | =over 8 |
435 | |
11e1c8f2 |
436 | =item 'E<lt>' read |
50b80e25 |
437 | |
11e1c8f2 |
438 | =item 'E<gt>' write |
50b80e25 |
439 | |
440 | =item '+' read/write |
441 | |
442 | =back |
443 | |
444 | B<imode> is C<O_BINARY> or C<O_TEXT>. |
445 | |
446 | B<layers> is a string of layers to apply, only ":raw" or :"crlf" make |
447 | sense in the non USE_PERLIO case. |
448 | |
449 | Portable cases are: |
450 | |
451 | PerlIO_binmode(f,ptype,O_BINARY,":raw"); |
452 | and |
453 | PerlIO_binmode(f,ptype,O_TEXT,":crlf"); |
454 | |
3039a93d |
455 | On Unix these calls probably have no effect whatsoever. |
50b80e25 |
456 | Elsewhere they alter "\n" to CR,LF translation and possibly cause a special |
457 | text "end of file" indicator to be written or honoured on read. The effect of |
458 | making the call after doing any IO to the handle depends on the implementation. (It may be |
459 | ignored, affect any data which is already buffered as well, or only apply |
460 | to subsequent data.) |
461 | |
462 | =item PerlIO_debug(fmt,...) |
463 | |
464 | PerlIO_debug is a printf()-like function which can be used for debugging. |
465 | No return value. Its main use is inside PerlIO where using real printf, warn() etc. would |
466 | recursively call PerlIO and be a problem. |
467 | |
468 | PerlIO_debug writes to the file named by $ENV{'PERLIO_DEBUG'} typical use |
469 | might be |
470 | |
50b80e25 |
471 | Bourne shells: |
472 | PERLIO_DEBUG=/dev/tty ./perl somescript some args |
473 | |
474 | Csh: |
475 | setenv PERLIO_DEBUG /dev/tty |
476 | ./perl somescript some args |
477 | |
478 | Win32: |
479 | set PERLIO_DEBUG=CON |
480 | perl somescript some args |
481 | |
482 | If $ENV{'PERLIO_DEBUG'} is not set PerlIO_debug() is a no-op. |
760ac839 |
483 | |
54310121 |
484 | =back |