| 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 | =item B<PerlIO_has_cntptr(f)> |
| 396 | |
| 397 | Implementation can return pointer to current position in the "buffer" |
| 398 | and a count of bytes available in the buffer. Do not use this - use |
| 399 | PerlIO_fast_gets. |
| 400 | |
| 401 | =item B<PerlIO_get_cnt(f)> |
| 402 | |
| 403 | Return count of readable bytes in the buffer. Zero or negative return |
| 404 | means no more bytes available. |
| 405 | |
| 406 | =item B<PerlIO_get_ptr(f)> |
| 407 | |
| 408 | Return pointer to next readable byte in buffer, accessing via the |
| 409 | pointer (dereferencing) is only safe if PerlIO_get_cnt() has returned |
| 410 | a positive value. Only positive offsets up to value returned by |
| 411 | PerlIO_get_cnt() are allowed. |
| 412 | |
| 413 | =item B<PerlIO_set_ptrcnt(f,p,c)> |
| 414 | |
| 415 | Set pointer into buffer, and a count of bytes still in the |
| 416 | buffer. Should be used only to set pointer to within range implied by |
| 417 | previous calls to C<PerlIO_get_ptr> and C<PerlIO_get_cnt>. The two |
| 418 | values I<must> be consistent with each other (implementation may only |
| 419 | use one or the other or may require both). |
| 420 | |
| 421 | =item B<PerlIO_canset_cnt(f)> |
| 422 | |
| 423 | Implementation can adjust its idea of number of bytes in the buffer. |
| 424 | Do not use this - use PerlIO_fast_gets. |
| 425 | |
| 426 | =item B<PerlIO_set_cnt(f,c)> |
| 427 | |
| 428 | Obscure - set count of bytes in the buffer. Deprecated. Only usable |
| 429 | if PerlIO_canset_cnt() returns true. Currently used in only doio.c to |
| 430 | force count less than -1 to -1. Perhaps should be PerlIO_set_empty or |
| 431 | similar. This call may actually do nothing if "count" is deduced from |
| 432 | pointer and a "limit". Do not use this - use PerlIO_set_ptrcnt(). |
| 433 | |
| 434 | =item B<PerlIO_has_base(f)> |
| 435 | |
| 436 | Returns true if implementation has a buffer, and can return pointer |
| 437 | to whole buffer and its size. Used by perl for B<-T> / B<-B> tests. |
| 438 | Other uses would be very obscure... |
| 439 | |
| 440 | =item B<PerlIO_get_base(f)> |
| 441 | |
| 442 | Return I<start> of buffer. Access only positive offsets in the buffer |
| 443 | up to the value returned by PerlIO_get_bufsiz(). |
| 444 | |
| 445 | =item B<PerlIO_get_bufsiz(f)> |
| 446 | |
| 447 | Return the I<total number of bytes> in the buffer, this is neither the |
| 448 | number that can be read, nor the amount of memory allocated to the |
| 449 | buffer. Rather it is what the operating system and/or implementation |
| 450 | happened to C<read()> (or whatever) last time IO was requested. |
| 451 | |
| 452 | =back |
| 453 | |
| 454 | =head2 Other Functions |
| 455 | |
| 456 | =over 4 |
| 457 | |
| 458 | =item PerlIO_apply_layers(f,mode,layers) |
| 459 | |
| 460 | The new interface to the USE_PERLIO implementation. The layers ":crlf" |
| 461 | and ":raw" are only ones allowed for other implementations and those |
| 462 | are silently ignored. (As of perl5.8 ":raw" is deprecated.) Use |
| 463 | PerlIO_binmode() below for the portable case. |
| 464 | |
| 465 | =item PerlIO_binmode(f,ptype,imode,layers) |
| 466 | |
| 467 | The hook used by perl's C<binmode> operator. |
| 468 | B<ptype> is perl's character for the kind of IO: |
| 469 | |
| 470 | =over 8 |
| 471 | |
| 472 | =item 'E<lt>' read |
| 473 | |
| 474 | =item 'E<gt>' write |
| 475 | |
| 476 | =item '+' read/write |
| 477 | |
| 478 | =back |
| 479 | |
| 480 | B<imode> is C<O_BINARY> or C<O_TEXT>. |
| 481 | |
| 482 | B<layers> is a string of layers to apply, only ":crlf" makes sense in |
| 483 | the non USE_PERLIO case. (As of perl5.8 ":raw" is deprecated in favour |
| 484 | of passing NULL.) |
| 485 | |
| 486 | Portable cases are: |
| 487 | |
| 488 | PerlIO_binmode(f,ptype,O_BINARY,NULL); |
| 489 | and |
| 490 | PerlIO_binmode(f,ptype,O_TEXT,":crlf"); |
| 491 | |
| 492 | On Unix these calls probably have no effect whatsoever. Elsewhere |
| 493 | they alter "\n" to CR,LF translation and possibly cause a special text |
| 494 | "end of file" indicator to be written or honoured on read. The effect |
| 495 | of making the call after doing any IO to the handle depends on the |
| 496 | implementation. (It may be ignored, affect any data which is already |
| 497 | buffered as well, or only apply to subsequent data.) |
| 498 | |
| 499 | =item PerlIO_debug(fmt,...) |
| 500 | |
| 501 | PerlIO_debug is a printf()-like function which can be used for |
| 502 | debugging. No return value. Its main use is inside PerlIO where using |
| 503 | real printf, warn() etc. would recursively call PerlIO and be a |
| 504 | problem. |
| 505 | |
| 506 | PerlIO_debug writes to the file named by $ENV{'PERLIO_DEBUG'} typical |
| 507 | use might be |
| 508 | |
| 509 | Bourne shells (sh, ksh, bash, zsh, ash, ...): |
| 510 | PERLIO_DEBUG=/dev/tty ./perl somescript some args |
| 511 | |
| 512 | Csh/Tcsh: |
| 513 | setenv PERLIO_DEBUG /dev/tty |
| 514 | ./perl somescript some args |
| 515 | |
| 516 | If you have the "env" utility: |
| 517 | env PERLIO_DEBUG=/dev/tty ./perl somescript some args |
| 518 | |
| 519 | Win32: |
| 520 | set PERLIO_DEBUG=CON |
| 521 | perl somescript some args |
| 522 | |
| 523 | If $ENV{'PERLIO_DEBUG'} is not set PerlIO_debug() is a no-op. |
| 524 | |
| 525 | =back |