Commit | Line | Data |
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760ac839 LW |
1 | =head1 NAME |
2 | ||
28757baa | 3 | perlapio - perl's IO abstraction interface. |
760ac839 LW |
4 | |
5 | =head1 SYNOPSIS | |
6 | ||
3039a93d | 7 | #define PERLIO_NOT_STDIO 0 /* For co-existence with stdio only */ |
50b80e25 NIS |
8 | #include <perlio.h> /* Usually via #include <perl.h> */ |
9 | ||
760ac839 LW |
10 | PerlIO *PerlIO_stdin(void); |
11 | PerlIO *PerlIO_stdout(void); | |
12 | PerlIO *PerlIO_stderr(void); | |
54310121 | 13 | |
50b80e25 NIS |
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 LW |
67 | |
68 | =head1 DESCRIPTION | |
69 | ||
06936a3c PN |
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. | |
760ac839 LW |
74 | |
75 | The functions are modeled on those in I<stdio.h>, but parameter order | |
76 | has been "tidied up a little". | |
77 | ||
06936a3c PN |
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). | |
50b80e25 NIS |
81 | |
82 | There are currently three implementations: | |
83 | ||
760ac839 LW |
84 | =over 4 |
85 | ||
50b80e25 | 86 | =item 1. USE_STDIO |
760ac839 | 87 | |
06936a3c PN |
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. | |
50b80e25 NIS |
92 | |
93 | =item 2. USE_SFIO | |
94 | ||
06936a3c PN |
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 *. | |
50b80e25 NIS |
99 | |
100 | =item 3. USE_PERLIO | |
101 | ||
06936a3c PN |
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 * | |
210b36aa | 107 | to remain with a known value while swapping the implementation around |
06936a3c PN |
108 | underneath I<at run time>. In this case all the above are true (but |
109 | very simple) functions which call the underlying implementation. | |
50b80e25 | 110 | |
06936a3c PN |
111 | This is the only implementation for which C<PerlIO_apply_layers()> |
112 | does anything "interesting". | |
50b80e25 NIS |
113 | |
114 | The USE_PERLIO implementation is described in L<perliol>. | |
115 | ||
116 | =back | |
117 | ||
06936a3c | 118 | Because "perlio.h" is a thin layer (for efficiency) the semantics of |
39ac7f1b LS |
119 | these functions are somewhat dependent on the underlying implementation. |
120 | Where these variations are understood they are noted below. | |
50b80e25 | 121 | |
39ac7f1b LS |
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. | |
50b80e25 NIS |
124 | |
125 | =over 4 | |
760ac839 LW |
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 | |
54310121 | 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 | |
760ac839 LW |
133 | values. |
134 | ||
135 | =item B<PerlIO_open(path, mode)>, B<PerlIO_fdopen(fd,mode)> | |
136 | ||
3039a93d | 137 | These correspond to fopen()/fdopen() and the arguments are the same. |
06936a3c PN |
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 | |
210b36aa | 141 | when C<NULL> is returned if this limit is exceeded. |
50b80e25 | 142 | |
11e1c8f2 | 143 | =item B<PerlIO_reopen(path,mode,f)> |
50b80e25 NIS |
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 | ||
06936a3c PN |
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. | |
760ac839 LW |
151 | |
152 | =item B<PerlIO_printf(f,fmt,...)>, B<PerlIO_vprintf(f,fmt,a)> | |
153 | ||
7b8d334a | 154 | These are fprintf()/vfprintf() equivalents. |
760ac839 LW |
155 | |
156 | =item B<PerlIO_stdoutf(fmt,...)> | |
157 | ||
158 | This is printf() equivalent. printf is #defined to this function, | |
84dc3c4d | 159 | so it is (currently) legal to use C<printf(fmt,...)> in perl sources. |
760ac839 LW |
160 | |
161 | =item B<PerlIO_read(f,buf,count)>, B<PerlIO_write(f,buf,count)> | |
162 | ||
06936a3c PN |
163 | These correspond to fread() and fwrite(). Note that arguments are |
164 | different, there is only one "count" and order has "file" | |
165 | first. Returns a byte count if successful (which may be zero), returns | |
166 | negative value and sets C<errno> on error. Depending on | |
167 | implementation C<errno> may be C<EINTR> if operation was interrupted | |
168 | by a signal. | |
760ac839 LW |
169 | |
170 | =item B<PerlIO_close(f)> | |
171 | ||
06936a3c PN |
172 | Depending on implementation C<errno> may be C<EINTR> if operation was |
173 | interrupted by a signal. | |
50b80e25 | 174 | |
21917246 | 175 | =item B<PerlIO_puts(f,s)>, B<PerlIO_putc(f,c)> |
760ac839 | 176 | |
54310121 | 177 | These correspond to fputs() and fputc(). |
760ac839 LW |
178 | Note that arguments have been revised to have "file" first. |
179 | ||
21917246 | 180 | =item B<PerlIO_ungetc(f,c)> |
760ac839 | 181 | |
06936a3c PN |
182 | This corresponds to ungetc(). Note that arguments have been revised |
183 | to have "file" first. Arranges that next read operation will return | |
184 | the byte B<c>. Despite the implied "character" in the name only | |
185 | values in the range 0..0xFF are defined. Returns the byte B<c> on | |
186 | success or -1 (C<EOF>) on error. The number of bytes that can be | |
187 | "pushed back" may vary, only 1 character is certain, and then only if | |
188 | it is the last character that was read from the handle. | |
760ac839 LW |
189 | |
190 | =item B<PerlIO_getc(f)> | |
191 | ||
192 | This corresponds to getc(). | |
50b80e25 | 193 | Despite the c in the name only byte range 0..0xFF is supported. |
3039a93d | 194 | Returns the character read or -1 (C<EOF>) on error. |
760ac839 LW |
195 | |
196 | =item B<PerlIO_eof(f)> | |
197 | ||
06936a3c PN |
198 | This corresponds to feof(). Returns a true/false indication of |
199 | whether the handle is at end of file. For terminal devices this may | |
200 | or may not be "sticky" depending on the implementation. The flag is | |
201 | cleared by PerlIO_seek(), or PerlIO_rewind(). | |
760ac839 LW |
202 | |
203 | =item B<PerlIO_error(f)> | |
204 | ||
06936a3c PN |
205 | This corresponds to ferror(). Returns a true/false indication of |
206 | whether there has been an IO error on the handle. | |
760ac839 LW |
207 | |
208 | =item B<PerlIO_fileno(f)> | |
209 | ||
06936a3c PN |
210 | This corresponds to fileno(), note that on some platforms, the meaning |
211 | of "fileno" may not match Unix. Returns -1 if the handle has no open | |
212 | descriptor associated with it. | |
760ac839 LW |
213 | |
214 | =item B<PerlIO_clearerr(f)> | |
215 | ||
06936a3c PN |
216 | This corresponds to clearerr(), i.e., clears 'error' and (usually) |
217 | 'eof' flags for the "stream". Does not return a value. | |
760ac839 LW |
218 | |
219 | =item B<PerlIO_flush(f)> | |
220 | ||
06936a3c PN |
221 | This corresponds to fflush(). Sends any buffered write data to the |
222 | underlying file. If called with C<NULL> this may flush all open | |
223 | streams (or core dump). Calling on a handle open for read only, or on | |
224 | which last operation was a read of some kind may lead to undefined | |
225 | behaviour. | |
760ac839 | 226 | |
50b80e25 | 227 | =item B<PerlIO_seek(f,offset,whence)> |
760ac839 | 228 | |
06936a3c PN |
229 | This corresponds to fseek(). Sends buffered write data to the |
230 | underlying file, or discards any buffered read data, then positions | |
231 | the file desciptor as specified by B<offset> and B<whence> (sic). | |
232 | This is the correct thing to do when switching between read and write | |
233 | on the same handle (see issues with PerlIO_flush() above). Offset is | |
234 | of type C<Off_t> which is a perl Configure value which may not be same | |
50b80e25 | 235 | as stdio's C<off_t>. |
760ac839 | 236 | |
50b80e25 | 237 | =item B<PerlIO_tell(f)> |
760ac839 | 238 | |
06936a3c PN |
239 | This corresponds to ftell(). Returns the current file position, or |
240 | (Off_t) -1 on error. May just return value system "knows" without | |
241 | making a system call or checking the underlying file descriptor (so | |
242 | use on shared file descriptors is not safe without a | |
243 | PerlIO_seek()). Return value is of type C<Off_t> which is a perl | |
244 | Configure value which may not be same as stdio's C<off_t>. | |
760ac839 LW |
245 | |
246 | =item B<PerlIO_getpos(f,p)>, B<PerlIO_setpos(f,p)> | |
247 | ||
06936a3c PN |
248 | These correspond (loosely) to fgetpos() and fsetpos(). Rather than |
249 | stdio's Fpos_t they expect a "Perl Scalar Value" to be passed. What is | |
250 | stored there should be considered opaque. The layout of the data may | |
251 | vary from handle to handle. When not using stdio or if platform does | |
252 | not have the stdio calls then they are implemented in terms of | |
253 | PerlIO_tell() and PerlIO_seek(). | |
760ac839 LW |
254 | |
255 | =item B<PerlIO_rewind(f)> | |
256 | ||
50b80e25 NIS |
257 | This corresponds to rewind(). It is usually defined as being |
258 | ||
259 | PerlIO_seek(f,(Off_t)0L, SEEK_SET); | |
260 | PerlIO_clearerr(f); | |
261 | ||
760ac839 LW |
262 | =item B<PerlIO_tmpfile()> |
263 | ||
06936a3c PN |
264 | This corresponds to tmpfile(), i.e., returns an anonymous PerlIO or |
265 | NULL on error. The system will attempt to automatically delete the | |
266 | file when closed. On Unix the file is usually C<unlink>-ed just after | |
267 | it is created so it does not matter how it gets closed. On other | |
268 | systems the file may only be deleted if closed via PerlIO_close() | |
269 | and/or the program exits via C<exit>. Depending on the implementation | |
270 | there may be "race conditions" which allow other processes access to | |
271 | the file, though in general it will be safer in this regard than | |
272 | ad. hoc. schemes. | |
50b80e25 NIS |
273 | |
274 | =item B<PerlIO_setlinebuf(f)> | |
275 | ||
06936a3c PN |
276 | This corresponds to setlinebuf(). Does not return a value. What |
277 | constitutes a "line" is implementation dependent but usually means | |
278 | that writing "\n" flushes the buffer. What happens with things like | |
279 | "this\nthat" is uncertain. (Perl core uses it I<only> when "dumping"; | |
280 | it has nothing to do with $| auto-flush.) | |
760ac839 | 281 | |
54310121 | 282 | =back |
760ac839 | 283 | |
510d21e9 | 284 | =head2 Co-existence with stdio |
760ac839 | 285 | |
510d21e9 | 286 | There is outline support for co-existence of PerlIO with stdio. |
06936a3c PN |
287 | Obviously if PerlIO is implemented in terms of stdio there is no |
288 | problem. However in other cases then mechanisms must exist to create a | |
289 | FILE * which can be passed to library code which is going to use stdio | |
290 | calls. | |
50b80e25 | 291 | |
210b36aa | 292 | The first step is to add this line: |
50b80e25 NIS |
293 | |
294 | #define PERLIO_NOT_STDIO 0 | |
295 | ||
06936a3c PN |
296 | I<before> including any perl header files. (This will probably become |
297 | the default at some point). That prevents "perlio.h" from attempting | |
298 | to #define stdio functions onto PerlIO functions. | |
50b80e25 | 299 | |
06936a3c PN |
300 | XS code is probably better using "typemap" if it expects FILE * |
301 | arguments. The standard typemap will be adjusted to comprehend any | |
302 | changes in this area. | |
760ac839 LW |
303 | |
304 | =over 4 | |
305 | ||
306 | =item B<PerlIO_importFILE(f,flags)> | |
307 | ||
06936a3c PN |
308 | Used to get a PerlIO * from a FILE *. May need additional arguments, |
309 | interface under review. | |
760ac839 | 310 | |
06936a3c PN |
311 | The flags argument was meant to be used for read vs write vs |
312 | read/write information. In hindsight it would have been better to make | |
313 | it a char *mode as in fopen/freopen. | |
50b80e25 | 314 | |
760ac839 LW |
315 | =item B<PerlIO_exportFILE(f,flags)> |
316 | ||
06936a3c PN |
317 | Given a PerlIO * return a 'native' FILE * suitable for passing to code |
318 | expecting to be compiled and linked with ANSI C I<stdio.h>. | |
760ac839 | 319 | |
06936a3c PN |
320 | The fact that such a FILE * has been 'exported' is recorded, and may |
321 | affect future PerlIO operations on the original PerlIO *. | |
760ac839 LW |
322 | |
323 | =item B<PerlIO_findFILE(f)> | |
324 | ||
06936a3c PN |
325 | Returns previously 'exported' FILE * (if any). Placeholder until |
326 | interface is fully defined. | |
760ac839 LW |
327 | |
328 | =item B<PerlIO_releaseFILE(p,f)> | |
329 | ||
06936a3c PN |
330 | Calling PerlIO_releaseFILE informs PerlIO that all use of FILE * is |
331 | complete. It is removed from list of 'exported' FILE *s, and | |
332 | associated PerlIO * should revert to original behaviour. | |
760ac839 | 333 | |
760ac839 LW |
334 | =back |
335 | ||
50b80e25 NIS |
336 | =head2 "Fast gets" Functions |
337 | ||
06936a3c PN |
338 | In addition to standard-like API defined so far above there is an |
339 | "implementation" interface which allows perl to get at internals of | |
340 | PerlIO. The following calls correspond to the various FILE_xxx macros | |
341 | determined by Configure - or their equivalent in other | |
342 | implementations. This section is really of interest to only those | |
343 | concerned with detailed perl-core behaviour, implementing a PerlIO | |
344 | mapping or writing code which can make use of the "read ahead" that | |
345 | has been done by the IO system in the same way perl does. Note that | |
346 | any code that uses these interfaces must be prepared to do things the | |
347 | traditional way if a handle does not support them. | |
760ac839 LW |
348 | |
349 | =over 4 | |
350 | ||
50b80e25 | 351 | =item B<PerlIO_fast_gets(f)> |
760ac839 | 352 | |
50b80e25 NIS |
353 | Returns true if implementation has all the interfaces required to |
354 | allow perl's C<sv_gets> to "bypass" normal IO mechanism. | |
355 | This can vary from handle to handle. | |
760ac839 | 356 | |
50b80e25 NIS |
357 | PerlIO_fast_gets(f) = PerlIO_has_cntptr(f) && \ |
358 | PerlIO_canset_cnt(f) && \ | |
359 | `Can set pointer into buffer' | |
760ac839 | 360 | |
760ac839 | 361 | |
50b80e25 | 362 | =item B<PerlIO_has_cntptr(f)> |
760ac839 | 363 | |
06936a3c PN |
364 | Implementation can return pointer to current position in the "buffer" |
365 | and a count of bytes available in the buffer. Do not use this - use | |
366 | PerlIO_fast_gets. | |
760ac839 | 367 | |
50b80e25 | 368 | =item B<PerlIO_get_cnt(f)> |
760ac839 | 369 | |
06936a3c PN |
370 | Return count of readable bytes in the buffer. Zero or negative return |
371 | means no more bytes available. | |
760ac839 | 372 | |
50b80e25 | 373 | =item B<PerlIO_get_ptr(f)> |
760ac839 | 374 | |
06936a3c PN |
375 | Return pointer to next readable byte in buffer, accessing via the |
376 | pointer (dereferencing) is only safe if PerlIO_get_cnt() has returned | |
377 | a positive value. Only positive offsets up to value returned by | |
378 | PerlIO_get_cnt() are allowed. | |
760ac839 LW |
379 | |
380 | =item B<PerlIO_set_ptrcnt(f,p,c)> | |
381 | ||
54310121 | 382 | Set pointer into buffer, and a count of bytes still in the |
06936a3c PN |
383 | buffer. Should be used only to set pointer to within range implied by |
384 | previous calls to C<PerlIO_get_ptr> and C<PerlIO_get_cnt>. The two | |
385 | values I<must> be consistent with each other (implementation may only | |
386 | use one or the other or may require both). | |
50b80e25 NIS |
387 | |
388 | =item B<PerlIO_canset_cnt(f)> | |
389 | ||
390 | Implementation can adjust its idea of number of bytes in the buffer. | |
391 | Do not use this - use PerlIO_fast_gets. | |
760ac839 LW |
392 | |
393 | =item B<PerlIO_set_cnt(f,c)> | |
394 | ||
06936a3c PN |
395 | Obscure - set count of bytes in the buffer. Deprecated. Only usable |
396 | if PerlIO_canset_cnt() returns true. Currently used in only doio.c to | |
397 | force count less than -1 to -1. Perhaps should be PerlIO_set_empty or | |
398 | similar. This call may actually do nothing if "count" is deduced from | |
399 | pointer and a "limit". Do not use this - use PerlIO_set_ptrcnt(). | |
760ac839 LW |
400 | |
401 | =item B<PerlIO_has_base(f)> | |
402 | ||
50b80e25 | 403 | Returns true if implementation has a buffer, and can return pointer |
760ac839 LW |
404 | to whole buffer and its size. Used by perl for B<-T> / B<-B> tests. |
405 | Other uses would be very obscure... | |
406 | ||
407 | =item B<PerlIO_get_base(f)> | |
408 | ||
50b80e25 NIS |
409 | Return I<start> of buffer. Access only positive offsets in the buffer |
410 | up to the value returned by PerlIO_get_bufsiz(). | |
760ac839 LW |
411 | |
412 | =item B<PerlIO_get_bufsiz(f)> | |
413 | ||
06936a3c PN |
414 | Return the I<total number of bytes> in the buffer, this is neither the |
415 | number that can be read, nor the amount of memory allocated to the | |
416 | buffer. Rather it is what the operating system and/or implementation | |
417 | happened to C<read()> (or whatever) last time IO was requested. | |
50b80e25 NIS |
418 | |
419 | =back | |
420 | ||
421 | =head2 Other Functions | |
422 | ||
423 | =over 4 | |
424 | ||
425 | =item PerlIO_apply_layers(f,mode,layers) | |
426 | ||
427 | The new interface to the USE_PERLIO implementation. The layers ":crlf" | |
428 | and ":raw" are only ones allowed for other implementations and those | |
429 | are silently ignored. Use PerlIO_binmode() below for the portable | |
430 | case. | |
431 | ||
432 | =item PerlIO_binmode(f,ptype,imode,layers) | |
433 | ||
434 | The hook used by perl's C<binmode> operator. | |
210b36aa | 435 | B<ptype> is perl's character for the kind of IO: |
50b80e25 NIS |
436 | |
437 | =over 8 | |
438 | ||
11e1c8f2 | 439 | =item 'E<lt>' read |
50b80e25 | 440 | |
11e1c8f2 | 441 | =item 'E<gt>' write |
50b80e25 NIS |
442 | |
443 | =item '+' read/write | |
444 | ||
445 | =back | |
446 | ||
447 | B<imode> is C<O_BINARY> or C<O_TEXT>. | |
448 | ||
449 | B<layers> is a string of layers to apply, only ":raw" or :"crlf" make | |
450 | sense in the non USE_PERLIO case. | |
451 | ||
452 | Portable cases are: | |
453 | ||
454 | PerlIO_binmode(f,ptype,O_BINARY,":raw"); | |
455 | and | |
456 | PerlIO_binmode(f,ptype,O_TEXT,":crlf"); | |
457 | ||
06936a3c PN |
458 | On Unix these calls probably have no effect whatsoever. Elsewhere |
459 | they alter "\n" to CR,LF translation and possibly cause a special text | |
460 | "end of file" indicator to be written or honoured on read. The effect | |
461 | of making the call after doing any IO to the handle depends on the | |
462 | implementation. (It may be ignored, affect any data which is already | |
463 | buffered as well, or only apply to subsequent data.) | |
50b80e25 NIS |
464 | |
465 | =item PerlIO_debug(fmt,...) | |
466 | ||
06936a3c PN |
467 | PerlIO_debug is a printf()-like function which can be used for |
468 | debugging. No return value. Its main use is inside PerlIO where using | |
469 | real printf, warn() etc. would recursively call PerlIO and be a | |
470 | problem. | |
50b80e25 | 471 | |
06936a3c PN |
472 | PerlIO_debug writes to the file named by $ENV{'PERLIO_DEBUG'} typical |
473 | use might be | |
50b80e25 | 474 | |
ada498b9 | 475 | Bourne shells (sh, ksh, bash, zsh, ash, ...): |
50b80e25 NIS |
476 | PERLIO_DEBUG=/dev/tty ./perl somescript some args |
477 | ||
ada498b9 | 478 | Csh/Tcsh: |
50b80e25 NIS |
479 | setenv PERLIO_DEBUG /dev/tty |
480 | ./perl somescript some args | |
481 | ||
ada498b9 SB |
482 | If you have the "env" utility: |
483 | env PERLIO_DEBUG=/dev/tty ./perl somescript some args | |
484 | ||
50b80e25 NIS |
485 | Win32: |
486 | set PERLIO_DEBUG=CON | |
487 | perl somescript some args | |
488 | ||
489 | If $ENV{'PERLIO_DEBUG'} is not set PerlIO_debug() is a no-op. | |
760ac839 | 490 | |
54310121 | 491 | =back |