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Portions of this text are reprinted and reproduced in electronic form in the Sun OS Reference Manual, from IEEE Std 1003.1, 2004 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2004 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between these versions and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html. 9 .\" This notice shall appear on any product containing this material. 10 .\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). 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If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] 13 .TH OPEN 2 "Jun 16, 2008" 14 .SH NAME 15 open, openat \- open a file 16 .SH SYNOPSIS 17 .LP 18 .nf 19 #include <sys/types.h> 20 #include <sys/stat.h> 21 #include <fcntl.h> 22 23 \fBint\fR \fBopen\fR(\fBconst char *\fR\fIpath\fR, \fBint\fR \fIoflag\fR, \fB/* mode_t\fR \fImode\fR */); 24 .fi 25 26 .LP 27 .nf 28 \fBint\fR \fBopenat\fR(\fBint\fR \fIfildes\fR, \fBconst char *\fR\fIpath\fR, \fBint\fR \fIoflag\fR, 29 \fB/* mode_t\fR \fImode\fR */); 30 .fi 31 32 .SH DESCRIPTION 33 .sp 34 .LP 35 The \fBopen()\fR function establishes the connection between a file and a file 36 descriptor. It creates an open file description that refers to a file and a 37 file descriptor that refers to that open file description. The file descriptor 38 is used by other I/O functions to refer to that file. The \fIpath\fR argument 39 points to a pathname naming the file. 40 .sp 41 .LP 42 The \fBopenat()\fR function is identical to the \fBopen()\fR function except 43 that the \fIpath\fR argument is interpreted relative to the starting point 44 implied by the \fIfildes\fR argument. If the \fIfildes\fR argument has the 45 special value \fBAT_FDCWD\fR, a relative path argument will be resolved 46 relative to the current working directory. If the \fIpath\fR argument is 47 absolute, the \fIfildes\fR argument is ignored. 48 .sp 49 .LP 50 The \fBopen()\fR function returns a file descriptor for the named file that is 51 the lowest file descriptor not currently open for that process. The open file 52 description is new, and therefore the file descriptor does not share it with 53 any other process in the system. The \fBFD_CLOEXEC\fR file descriptor flag 54 associated with the new file descriptor is cleared. 55 .sp 56 .LP 57 The file offset used to mark the current position within the file is set to the 58 beginning of the file. 59 .sp 60 .LP 61 The file status flags and file access modes of the open file description are 62 set according to the value of \fIoflag\fR. The \fImode\fR argument is used only 63 when \fBO_CREAT\fR is specified (see below.) 64 .sp 65 .LP 66 Values for \fIoflag\fR are constructed by a bitwise-inclusive-OR of flags from 67 the following list, defined in <\fBfcntl.h\fR>. Applications must specify 68 exactly one of the first three values (file access modes) below in the value of 69 \fIoflag\fR: 70 .sp 71 .ne 2 72 .na 73 \fB\fBO_RDONLY\fR\fR 74 .ad 75 .RS 12n 76 Open for reading only. 77 .RE 78 79 .sp 80 .ne 2 81 .na 82 \fB\fBO_WRONLY\fR\fR 83 .ad 84 .RS 12n 85 Open for writing only. 86 .RE 87 88 .sp 89 .ne 2 90 .na 91 \fB\fBO_RDWR\fR\fR 92 .ad 93 .RS 12n 94 Open for reading and writing. The result is undefined if this flag is applied 95 to a FIFO. 96 .RE 97 98 .sp 99 .LP 100 Any combination of the following may be used: 101 .sp 102 .ne 2 103 .na 104 \fB\fBO_APPEND\fR\fR 105 .ad 106 .sp .6 107 .RS 4n 108 If set, the file offset is set to the end of the file prior to each write. 109 .RE 110 111 .sp 112 .ne 2 113 .na 114 \fB\fBO_CREAT\fR\fR 115 .ad 116 .sp .6 117 .RS 4n 118 Create the file if it does not exist. This flag requires that the \fImode\fR 119 argument be specified. 120 .sp 121 If the file exists, this flag has no effect except as noted under \fBO_EXCL\fR 122 below. Otherwise, the file is created with the user \fBID\fR of the file set 123 to the effective user \fBID\fR of the process. The group \fBID\fR of the file 124 is set to the effective group \fBIDs\fR of the process, or if the \fBS_ISGID\fR 125 bit is set in the directory in which the file is being created, the file's 126 group \fBID\fR is set to the group \fBID\fR of its parent directory. If the 127 group \fBID\fR of the new file does not match the effective group \fBID\fR or 128 one of the supplementary groups IDs, the \fBS_ISGID\fR bit is cleared. The 129 access permission bits (see \fB<sys/stat.h>\fR) of the file mode are set to the 130 value of \fImode\fR, modified as follows (see \fBcreat\fR(2)): a bitwise-AND is 131 performed on the file-mode bits and the corresponding bits in the complement of 132 the process's file mode creation mask. Thus, all bits set in the process's file 133 mode creation mask (see \fBumask\fR(2)) are correspondingly cleared in the 134 file's permission mask. The "save text image after execution bit" of the mode 135 is cleared (see \fBchmod\fR(2)). \fBO_SYNC\fR Write I/O operations on the file 136 descriptor complete as defined by synchronized I/O file integrity completion 137 (see \fBfcntl.h\fR(3HEAD) definition of \fBO_SYNC\fR.) When bits other than the 138 file permission bits are set, the effect is unspecified. The \fImode\fR 139 argument does not affect whether the file is open for reading, writing or for 140 both. 141 .RE 142 143 .sp 144 .ne 2 145 .na 146 \fB\fBO_DSYNC\fR\fR 147 .ad 148 .sp .6 149 .RS 4n 150 Write I/O operations on the file descriptor complete as defined by synchronized 151 I/O data integrity completion. 152 .RE 153 154 .sp 155 .ne 2 156 .na 157 \fB\fBO_EXCL\fR\fR 158 .ad 159 .sp .6 160 .RS 4n 161 If \fBO_CREAT\fR and \fBO_EXCL\fR are set, \fBopen()\fR fails if the file 162 exists. The check for the existence of the file and the creation of the file if 163 it does not exist is atomic with respect to other threads executing 164 \fBopen()\fR naming the same filename in the same directory with \fBO_EXCL\fR 165 and \fBO_CREAT\fR set. If \fBO_EXCL\fR and \fBO_CREAT\fR are set, and path 166 names a symbolic link, \fBopen()\fR fails and sets \fBerrno\fR to \fBEEXIST\fR, 167 regardless of the contents of the symbolic link. If \fBO_EXCL\fR is set and 168 \fBO_CREAT\fR is not set, the result is undefined. 169 .RE 170 171 .sp 172 .ne 2 173 .na 174 \fB\fBO_LARGEFILE\fR\fR 175 .ad 176 .sp .6 177 .RS 4n 178 If set, the offset maximum in the open file description is the largest value 179 that can be represented correctly in an object of type \fBoff64_t\fR. 180 .RE 181 182 .sp 183 .ne 2 184 .na 185 \fB\fBO_NOCTTY\fR\fR 186 .ad 187 .sp .6 188 .RS 4n 189 If set and \fIpath\fR identifies a terminal device, \fBopen()\fR does not cause 190 the terminal device to become the controlling terminal for the process. 191 .RE 192 193 .sp 194 .ne 2 195 .na 196 \fB\fBO_NOFOLLOW\fR\fR 197 .ad 198 .sp .6 199 .RS 4n 200 If the path names a symbolic link, \fBopen()\fR fails and sets \fBerrno\fR to 201 \fBELOOP\fR. 202 .RE 203 204 .sp 205 .ne 2 206 .na 207 \fB\fBO_NOLINKS\fR\fR 208 .ad 209 .sp .6 210 .RS 4n 211 If the link count of the named file is greater than 1, \fBopen()\fR fails and 212 sets \fBerrno\fR to \fBEMLINK\fR. 213 .RE 214 215 .sp 216 .ne 2 217 .na 218 \fB\fBO_CLOEXEC\fR\fR 219 .ad 220 .sp .6 221 .RS 4n 222 If set, the filedescriptor returned will be closed prior to any future 223 \fBexec()\fR calls. 224 .RE 225 226 .sp 227 .ne 2 228 .na 229 \fB\fBO_NONBLOCK\fR or \fBO_NDELAY\fR\fR 230 .ad 231 .sp .6 232 .RS 4n 233 These flags can affect subsequent reads and writes (see \fBread\fR(2) and 234 \fBwrite\fR(2)). If both \fBO_NDELAY\fR and \fBO_NONBLOCK\fR are set, 235 \fBO_NONBLOCK\fR takes precedence. 236 .sp 237 When opening a \fBFIFO\fR with \fBO_RDONLY\fR or \fBO_WRONLY\fR set: 238 .RS +4 239 .TP 240 .ie t \(bu 241 .el o 242 If \fBO_NONBLOCK\fR or \fBO_NDELAY\fR is set, an \fBopen()\fR for reading only 243 returns without delay. An \fBopen()\fR for writing only returns an error if no 244 process currently has the file open for reading. 245 .RE 246 .RS +4 247 .TP 248 .ie t \(bu 249 .el o 250 If \fBO_NONBLOCK\fR and \fBO_NDELAY\fR are clear, an \fBopen()\fR for reading 251 only blocks until a thread opens the file for writing. An \fBopen()\fR for 252 writing only blocks the calling thread until a thread opens the file for 253 reading. 254 .RE 255 After both ends of a \fBFIFO\fR have been opened, there is no guarantee that 256 further calls to \fBopen()\fR \fBO_RDONLY\fR (\fBO_WRONLY\fR) will synchronize 257 with later calls to \fBopen()\fR \fBO_WRONLY\fR (\fBO_RDONLY\fR) until both 258 ends of the \fBFIFO\fR have been closed by all readers and writers. Any data 259 written into a \fBFIFO\fR will be lost if both ends of the \fBFIFO\fR are 260 closed before the data is read. 261 .sp 262 When opening a block special or character special file that supports 263 non-blocking opens: 264 .RS +4 265 .TP 266 .ie t \(bu 267 .el o 268 If \fBO_NONBLOCK\fR or \fBO_NDELAY\fR is set, the \fBopen()\fR function returns 269 without blocking for the device to be ready or available. Subsequent behavior 270 of the device is device-specific. 271 .RE 272 .RS +4 273 .TP 274 .ie t \(bu 275 .el o 276 If \fBO_NONBLOCK\fR and \fBO_NDELAY\fR are clear, the \fBopen()\fR function 277 blocks the calling thread until the device is ready or available before 278 returning. 279 .RE 280 Otherwise, the behavior of \fBO_NONBLOCK\fR and \fBO_NDELAY\fR is unspecified. 281 .RE 282 283 .sp 284 .ne 2 285 .na 286 \fB\fBO_RSYNC\fR\fR 287 .ad 288 .sp .6 289 .RS 4n 290 Read I/O operations on the file descriptor complete at the same level of 291 integrity as specified by the \fBO_DSYNC\fR and \fBO_SYNC\fR flags. If both 292 \fBO_DSYNC\fR and \fBO_RSYNC\fR are set in \fIoflag\fR, all I/O operations on 293 the file descriptor complete as defined by synchronized I/O data integrity 294 completion. If both \fBO_SYNC\fR and \fBO_RSYNC\fR are set in \fIoflag\fR, all 295 I/O operations on the file descriptor complete as defined by synchronized I/O 296 file integrity completion. 297 .RE 298 299 .sp 300 .ne 2 301 .na 302 \fB\fBO_SYNC\fR\fR 303 .ad 304 .sp .6 305 .RS 4n 306 Write I/O operations on the file descriptor complete as defined by synchronized 307 I/O file integrity completion. 308 .RE 309 310 .sp 311 .ne 2 312 .na 313 \fB\fBO_TRUNC\fR\fR 314 .ad 315 .sp .6 316 .RS 4n 317 If the file exists and is a regular file, and the file is successfully opened 318 \fBO_RDWR\fR or \fBO_WRONLY\fR, its length is truncated to 0 and the mode and 319 owner are unchanged. It has no effect on \fBFIFO\fR special files or terminal 320 device files. Its effect on other file types is implementation-dependent. The 321 result of using \fBO_TRUNC\fR with \fBO_RDONLY\fR is undefined. 322 .RE 323 324 .sp 325 .ne 2 326 .na 327 \fB\fBO_XATTR\fR\fR 328 .ad 329 .sp .6 330 .RS 4n 331 If set in \fBopenat()\fR, a relative path argument is interpreted as a 332 reference to an extended attribute of the file associated with the supplied 333 file descriptor. This flag therefore requires the presence of a legal 334 \fIfildes\fR argument. If set in \fBopen()\fR, the implied file descriptor is 335 that for the current working directory. Extended attributes must be referenced 336 with a relative path; providing an absolute path results in a normal file 337 reference. 338 .RE 339 340 .sp 341 .LP 342 If \fBO_CREAT\fR is set and the file did not previously exist, upon successful 343 completion, \fBopen()\fR marks for update the \fBst_atime\fR, \fBst_ctime\fR, 344 and \fBst_mtime\fR fields of the file and the \fBst_ctime\fR and \fBst_mtime\fR 345 fields of the parent directory. 346 .sp 347 .LP 348 If \fBO_TRUNC\fR is set and the file did previously exist, upon successful 349 completion, \fBopen()\fR marks for update the \fBst_ctime\fR and \fBst_mtime\fR 350 fields of the file. 351 .sp 352 .LP 353 If both the \fBO_SYNC\fR and \fBO_DSYNC\fR flags are set, the effect is as if 354 only the \fBO_SYNC\fR flag was set. 355 .sp 356 .LP 357 If \fIpath\fR refers to a \fBSTREAMS\fR file, \fIoflag\fR may be constructed 358 from \fBO_NONBLOCK\fR or \fBO_NODELAY\fR OR-ed with either \fBO_RDONLY\fR, 359 \fBO_WRONLY\fR, or \fBO_RDWR\fR. Other flag values are not applicable to 360 \fBSTREAMS\fR devices and have no effect on them. The values \fBO_NONBLOCK\fR 361 and \fBO_NODELAY\fR affect the operation of \fBSTREAMS\fR drivers and certain 362 functions (see \fBread\fR(2), \fBgetmsg\fR(2), \fBputmsg\fR(2), and 363 \fBwrite\fR(2)) applied to file descriptors associated with \fBSTREAMS\fR 364 files. For \fBSTREAMS\fR drivers, the implementation of \fBO_NONBLOCK\fR and 365 \fBO_NODELAY\fR is device-specific. 366 .sp 367 .LP 368 When \fBopen()\fR is invoked to open a named stream, and the \fBconnld\fR 369 module (see \fBconnld\fR(7M)) has been pushed on the pipe, \fBopen()\fR blocks 370 until the server process has issued an \fBI_RECVFD\fR \fBioctl()\fR (see 371 \fBstreamio\fR(7I)) to receive the file descriptor. 372 .sp 373 .LP 374 If \fIpath\fR names the master side of a pseudo-terminal device, then it is 375 unspecified whether \fBopen()\fR locks the slave side so that it cannot be 376 opened. Portable applications must call \fBunlockpt\fR(3C) before opening the 377 slave side. 378 .sp 379 .LP 380 If the file is a regular file and the local file system is mounted with the 381 \fBnbmand\fR mount option, then a mandatory share reservation is automatically 382 obtained on the file. The share reservation is obtained as if \fBfcntl\fR(2) 383 were called with \fIcmd\fR \fBF_SHARE_NBMAND\fR and the \fBfshare_t\fR values 384 set as follows: 385 .sp 386 .ne 2 387 .na 388 \fB\fBf_access\fR\fR 389 .ad 390 .RS 12n 391 Set to the type of read/write access for which the file is opened. 392 .RE 393 394 .sp 395 .ne 2 396 .na 397 \fB\fBf_deny\fR\fR 398 .ad 399 .RS 12n 400 \fBF_NODNY\fR 401 .RE 402 403 .sp 404 .ne 2 405 .na 406 \fB\fBf_id\fR\fR 407 .ad 408 .RS 12n 409 The file descriptor value returned from \fBopen()\fR. 410 .RE 411 412 .sp 413 .LP 414 If \fIpath\fR is a symbolic link and \fBO_CREAT\fR and \fBO_EXCL\fR are set, 415 the link is not followed. 416 .sp 417 .LP 418 Certain flag values can be set following \fBopen()\fR as described in 419 \fBfcntl\fR(2). 420 .sp 421 .LP 422 The largest value that can be represented correctly in an object of type 423 \fBoff_t\fR is established as the offset maximum in the open file description. 424 .SH RETURN VALUES 425 .sp 426 .LP 427 Upon successful completion, the \fBopen()\fR function opens the file and return 428 a non-negative integer representing the lowest numbered unused file descriptor. 429 Otherwise, \fB\(mi1\fR is returned, \fBerrno\fR is set to indicate the error, 430 and no files are created or modified. 431 .SH ERRORS 432 .sp 433 .LP 434 The \fBopen()\fR and \fBopenat()\fR functions will fail if: 435 .sp 436 .ne 2 437 .na 438 \fB\fBEACCES\fR\fR 439 .ad 440 .RS 16n 441 Search permission is denied on a component of the path prefix. 442 .sp 443 The file exists and the permissions specified by \fIoflag\fR are denied. 444 .sp 445 The file does not exist and write permission is denied for the parent directory 446 of the file to be created. 447 .sp 448 \fBO_TRUNC\fR is specified and write permission is denied. 449 .sp 450 The {\fBPRIV_FILE_DAC_SEARCH\fR} privilege allows processes to search 451 directories regardless of permission bits. The {\fBPRIV_FILE_DAC_WRITE\fR} 452 privilege allows processes to open files for writing regardless of permission 453 bits. See \fBprivileges\fR(5) for special considerations when opening files 454 owned by UID 0 for writing. The {\fBPRIV_FILE_DAC_READ\fR} privilege allows 455 processes to open files for reading regardless of permission bits. 456 .RE 457 458 .sp 459 .ne 2 460 .na 461 \fB\fBEAGAIN\fR\fR 462 .ad 463 .RS 16n 464 A mandatory share reservation could not be obtained because the desired access 465 conflicts with an existing \fBf_deny\fR share reservation. 466 .RE 467 468 .sp 469 .ne 2 470 .na 471 \fB\fBEBADF\fR\fR 472 .ad 473 .RS 16n 474 The file descriptor provided to \fBopenat()\fR is invalid. 475 .RE 476 477 .sp 478 .ne 2 479 .na 480 \fB\fBEDQUOT\fR\fR 481 .ad 482 .RS 16n 483 The file does not exist, \fBO_CREAT\fR is specified, and either the directory 484 where the new file entry is being placed cannot be extended because the user's 485 quota of disk blocks on that file system has been exhausted, or the user's 486 quota of inodes on the file system where the file is being created has been 487 exhausted. 488 .RE 489 490 .sp 491 .ne 2 492 .na 493 \fB\fBEEXIST\fR\fR 494 .ad 495 .RS 16n 496 The \fBO_CREAT\fR and \fBO_EXCL\fR flags are set and the named file exists. 497 .RE 498 499 .sp 500 .ne 2 501 .na 502 \fB\fBEILSEQ\fR\fR 503 .ad 504 .RS 16n 505 The \fIpath\fR argument includes non-UTF8 characters and the file system 506 accepts only file names where all characters are part of the UTF-8 character 507 codeset. 508 .RE 509 510 .sp 511 .ne 2 512 .na 513 \fB\fBEINTR\fR\fR 514 .ad 515 .RS 16n 516 A signal was caught during \fBopen()\fR. 517 .RE 518 519 .sp 520 .ne 2 521 .na 522 \fB\fBEFAULT\fR\fR 523 .ad 524 .RS 16n 525 The \fIpath\fR argument points to an illegal address. 526 .RE 527 528 .sp 529 .ne 2 530 .na 531 \fB\fBEINVAL\fR\fR 532 .ad 533 .RS 16n 534 The system does not support synchronized I/O for this file, or the 535 \fBO_XATTR\fR flag was supplied and the underlying file system does not support 536 extended file attributes. 537 .RE 538 539 .sp 540 .ne 2 541 .na 542 \fB\fBEIO\fR\fR 543 .ad 544 .RS 16n 545 The \fIpath\fR argument names a \fBSTREAMS\fR file and a hangup or error 546 occurred during the \fBopen()\fR. 547 .RE 548 549 .sp 550 .ne 2 551 .na 552 \fB\fBEISDIR\fR\fR 553 .ad 554 .RS 16n 555 The named file is a directory and \fIoflag\fR includes \fBO_WRONLY\fR or 556 \fBO_RDWR\fR. 557 .RE 558 559 .sp 560 .ne 2 561 .na 562 \fB\fBELOOP\fR\fR 563 .ad 564 .RS 16n 565 Too many symbolic links were encountered in resolving \fIpath\fR. 566 .sp 567 A loop exists in symbolic links encountered during resolution of the \fIpath\fR 568 argument. 569 .sp 570 The \fBO_NOFOLLOW\fR flag is set and the final component of path is a symbolic 571 link. 572 .RE 573 574 .sp 575 .ne 2 576 .na 577 \fB\fBEMFILE\fR\fR 578 .ad 579 .RS 16n 580 There are currently {\fBOPEN_MAX\fR} file descriptors open in the calling 581 process. 582 .RE 583 584 .sp 585 .ne 2 586 .na 587 \fB\fBEMLINK\fR\fR 588 .ad 589 .RS 16n 590 The \fBO_NOLINKS\fR flag is set and the named file has a link count greater 591 than 1. 592 .RE 593 594 .sp 595 .ne 2 596 .na 597 \fB\fBEMULTIHOP\fR\fR 598 .ad 599 .RS 16n 600 Components of \fIpath\fR require hopping to multiple remote machines and the 601 file system does not allow it. 602 .RE 603 604 .sp 605 .ne 2 606 .na 607 \fB\fBENAMETOOLONG\fR\fR 608 .ad 609 .RS 16n 610 The length of the \fIpath\fR argument exceeds {\fBPATH_MAX\fR} or a pathname 611 component is longer than {\fBNAME_MAX\fR}. 612 .RE 613 614 .sp 615 .ne 2 616 .na 617 \fB\fBENFILE\fR\fR 618 .ad 619 .RS 16n 620 The maximum allowable number of files is currently open in the system. 621 .RE 622 623 .sp 624 .ne 2 625 .na 626 \fB\fBENOENT\fR\fR 627 .ad 628 .RS 16n 629 The \fBO_CREAT\fR flag is not set and the named file does not exist; or the 630 \fBO_CREAT\fR flag is set and either the path prefix does not exist or the 631 \fIpath\fR argument points to an empty string. 632 .RE 633 634 .sp 635 .ne 2 636 .na 637 \fB\fBENOLINK\fR\fR 638 .ad 639 .RS 16n 640 The \fIpath\fR argument points to a remote machine, and the link to that 641 machine is no longer active. 642 .RE 643 644 .sp 645 .ne 2 646 .na 647 \fB\fBENOSR\fR\fR 648 .ad 649 .RS 16n 650 The \fIpath\fR argument names a STREAMS-based file and the system is unable to 651 allocate a STREAM. 652 .RE 653 654 .sp 655 .ne 2 656 .na 657 \fB\fBENOSPC\fR\fR 658 .ad 659 .RS 16n 660 The directory or file system that would contain the new file cannot be 661 expanded, the file does not exist, and \fBO_CREAT\fR is specified. 662 .RE 663 664 .sp 665 .ne 2 666 .na 667 \fB\fBENOSYS\fR\fR 668 .ad 669 .RS 16n 670 The device specified by \fIpath\fR does not support the open operation. 671 .RE 672 673 .sp 674 .ne 2 675 .na 676 \fB\fBENOTDIR\fR\fR 677 .ad 678 .RS 16n 679 A component of the path prefix is not a directory or a relative path was 680 supplied to \fBopenat()\fR, the \fBO_XATTR\fR flag was not supplied, and the 681 file descriptor does not refer to a directory. 682 .RE 683 684 .sp 685 .ne 2 686 .na 687 \fB\fBENXIO\fR\fR 688 .ad 689 .RS 16n 690 The \fBO_NONBLOCK\fR flag is set, the named file is a FIFO, the \fBO_WRONLY\fR 691 flag is set, and no process has the file open for reading; or the named file is 692 a character special or block special file and the device associated with this 693 special file does not exist or has been retired by the fault management 694 framework . 695 .RE 696 697 .sp 698 .ne 2 699 .na 700 \fB\fBEOPNOTSUPP\fR\fR 701 .ad 702 .RS 16n 703 An attempt was made to open a path that corresponds to a \fBAF_UNIX\fR socket. 704 .RE 705 706 .sp 707 .ne 2 708 .na 709 \fB\fBEOVERFLOW\fR\fR 710 .ad 711 .RS 16n 712 The named file is a regular file and either \fBO_LARGEFILE\fR is not set and 713 the size of the file cannot be represented correctly in an object of type 714 \fBoff_t\fR or \fBO_LARGEFILE\fR is set and the size of the file cannot be 715 represented correctly in an object of type \fBoff64_t\fR. 716 .RE 717 718 .sp 719 .ne 2 720 .na 721 \fB\fBEROFS\fR\fR 722 .ad 723 .RS 16n 724 The named file resides on a read-only file system and either \fBO_WRONLY\fR, 725 \fBO_RDWR\fR, \fBO_CREAT\fR (if file does not exist), or \fBO_TRUNC\fR is set 726 in the \fIoflag\fR argument. 727 .RE 728 729 .sp 730 .LP 731 The \fBopenat()\fR function will fail if: 732 .sp 733 .ne 2 734 .na 735 \fB\fBEBADF\fR\fR 736 .ad 737 .RS 9n 738 The \fIfildes\fR argument is not a valid open file descriptor or is not 739 \fBAT_FTCWD\fR. 740 .RE 741 742 .sp 743 .LP 744 The \fBopen()\fR function may fail if: 745 .sp 746 .ne 2 747 .na 748 \fB\fBEAGAIN\fR\fR 749 .ad 750 .RS 16n 751 The \fIpath\fR argument names the slave side of a pseudo-terminal device that 752 is locked. 753 .RE 754 755 .sp 756 .ne 2 757 .na 758 \fB\fBEINVAL\fR\fR 759 .ad 760 .RS 16n 761 The value of the \fIoflag\fR argument is not valid. 762 .RE 763 764 .sp 765 .ne 2 766 .na 767 \fB\fBENAMETOOLONG\fR\fR 768 .ad 769 .RS 16n 770 Pathname resolution of a symbolic link produced an intermediate result whose 771 length exceeds {\fBPATH_MAX\fR}. 772 .RE 773 774 .sp 775 .ne 2 776 .na 777 \fB\fBENOMEM\fR\fR 778 .ad 779 .RS 16n 780 The \fIpath\fR argument names a \fBSTREAMS\fR file and the system is unable to 781 allocate resources. 782 .RE 783 784 .sp 785 .ne 2 786 .na 787 \fB\fBETXTBSY\fR\fR 788 .ad 789 .RS 16n 790 The file is a pure procedure (shared text) file that is being executed and 791 \fIoflag\fR is \fBO_WRONLY\fR or \fBO_RDWR\fR. 792 .RE 793 794 .SH EXAMPLES 795 .LP 796 \fBExample 1 \fROpen a file for writing by the owner. 797 .sp 798 .LP 799 The following example opens the file \fB/tmp/file\fR, either by creating it if 800 it does not already exist, or by truncating its length to 0 if it does exist. 801 If the call creates a new file, the access permission bits in the file mode of 802 the file are set to permit reading and writing by the owner, and to permit 803 reading only by group members and others. 804 805 .sp 806 .LP 807 If the call to \fBopen()\fR is successful, the file is opened for writing. 808 809 .sp 810 .in +2 811 .nf 812 #include <fcntl.h> 813 \&... 814 int fd; 815 mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH; 816 char *filename = "/tmp/file"; 817 \&... 818 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, mode); 819 \&... 820 .fi 821 .in -2 822 823 .LP 824 \fBExample 2 \fROpen a file using an existence check. 825 .sp 826 .LP 827 The following example uses the \fBopen()\fR function to try to create the 828 \fBLOCKFILE\fR file and open it for writing. Since the \fBopen()\fR function 829 specifies the \fBO_EXCL\fR flag, the call fails if the file already exists. In 830 that case, the application assumes that someone else is updating the password 831 file and exits. 832 833 .sp 834 .in +2 835 .nf 836 #include <fcntl.h> 837 #include <stdio.h> 838 #include <stdlib.h> 839 #define LOCKFILE "/etc/ptmp" 840 \&... 841 int pfd; /* Integer for file descriptor returned by open() call. */ 842 \&... 843 if ((pfd = open(LOCKFILE, O_WRONLY | O_CREAT | O_EXCL, 844 S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) == -1) 845 { 846 fprintf(stderr, "Cannot open /etc/ptmp. Try again later.\en"); 847 exit(1); 848 } 849 \&... 850 .fi 851 .in -2 852 853 .LP 854 \fBExample 3 \fROpen a file for writing. 855 .sp 856 .LP 857 The following example opens a file for writing, creating the file if it does 858 not already exist. If the file does exist, the system truncates the file to 859 zero bytes. 860 861 .sp 862 .in +2 863 .nf 864 #include <fcntl.h> 865 #include <stdio.h> 866 #include <stdlib.h> 867 #define LOCKFILE "/etc/ptmp" 868 \&... 869 int pfd; 870 char filename[PATH_MAX+1]; 871 \&... 872 if ((pfd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 873 S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)) == -1) 874 { 875 perror("Cannot open output file\en"); exit(1); 876 } 877 \&... 878 .fi 879 .in -2 880 881 .SH USAGE 882 .sp 883 .LP 884 The \fBopen()\fR function has a transitional interface for 64-bit file offsets. 885 See \fBlf64\fR(5). Note that using \fBopen64()\fR is equivalent to using 886 \fBopen()\fR with \fBO_LARGEFILE\fR set in \fIoflag\fR. 887 .SH ATTRIBUTES 888 .sp 889 .LP 890 See \fBattributes\fR(5) for descriptions of the following attributes: 891 .sp 892 893 .sp 894 .TS 895 box; 896 c | c 897 l | l . 898 ATTRIBUTE TYPE ATTRIBUTE VALUE 899 _ 900 Interface Stability Committed 901 _ 902 MT-Level Async-Signal-Safe 903 _ 904 Standard For \fBopen()\fR, see \fBstandards\fR(5). 905 .TE 906 907 .SH SEE ALSO 908 .sp 909 .LP 910 \fBIntro\fR(2), \fBchmod\fR(2), \fBclose\fR(2), \fBcreat\fR(2), \fBdup\fR(2), 911 \fBexec\fR(2), \fBfcntl\fR(2), \fBgetmsg\fR(2), \fBgetrlimit\fR(2), 912 \fBlseek\fR(2), \fBputmsg\fR(2), \fBread\fR(2), \fBstat\fR(2), \fBumask\fR(2), 913 \fBwrite\fR(2), \fBattropen\fR(3C), \fBfcntl.h\fR(3HEAD), \fBstat.h\fR(3HEAD), 914 \fBunlockpt\fR(3C), \fBattributes\fR(5), \fBlf64\fR(5), \fBprivileges\fR(5), 915 \fBstandards\fR(5), \fBconnld\fR(7M), \fBstreamio\fR(7I) 916 .SH NOTES 917 .sp 918 .LP 919 Hierarchical Storage Management (HSM) file systems can sometimes cause long 920 delays when opening a file, since HSM files must be recalled from secondary 921 storage.