open(2)
open - open for reading or writing
As shipped in IRIX 6.5. First release of IRIX 6.5.
NAME open - open for reading or writing C SYNOPSIS #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> int open (const char *path, int oflag, ... /* mode_t mode */); DESCRIPTION path points to a path name naming a file. open opens a file descriptor for the named file and sets the file status flags according to the value of oflag. oflag values are constructed by OR-ing Flags from the following list (only one of the first three flags below may be used): O_RDONLY Open for reading only. O_WRONLY Open for writing only. O_RDWR Open for reading and writing. O_NDELAY or O_NONBLOCK These flags may affect subsequent reads and writes [see read(2) and write(2)]. If both O_NDELAY and O_NONBLOCK are set, O_NONBLOCK will take precedence. When opening a FIFO with O_RDONLY or O_WRONLY set: If O_NDELAY or O_NONBLOCK is set: An open for reading- only will return without delay; an open for writing-only will return an error if no process currently has the file open for reading. If O_NDELAY and O_NONBLOCK are clear: An open for reading-only will block until a process opens the file for writing; an open for writing-only will block until a process opens the file for reading. When opening a file associated with a communication line: If O_NDELAY or O_NONBLOCK is set: The open will return without waiting for the device to be ready or available; subsequent behavior of the device is device specific. If O_NDELAY and O_NONBLOCK are clear: The open will block until the device is ready or available. O_APPEND If set, the file pointer will be set to the end of the file prior to each write. O_SYNC When opening a regular file, this flag affects subsequent writes. If set, each write(2) will wait for both the file data and file status to be physically updated. O_DSYNCWhen opening a regular file, this flag affects subsequent writes. If set, each write(2) will wait for the file data to be physically updated. O_RSYNCWhen opening a regular file, this flag affects subsequent reads. If set, and either O_SYNC or O_DSYNC is set then each read(2) will wait for the file to be in the same state as O_SYNC or O_DSYNC would require for writes. O_NOCTTY If set and the file is a terminal, the terminal will not be allocated as the calling process's controlling terminal. O_CREATIf the file exists, this flag has no effect, except as noted under O_EXCL below. Otherwise, the file is created and the owner ID of the file is set to the effective user IDs of the process, the group ID of the file is set to the effective group IDs of the process or to the group ID of the directory in which the file is being created. This is determined as follows: If the underlying filesystem was mounted with the BSD file creation semantics flag [see fstab(4)] or the S_ISGID bit is set [see chmod(2)] on the parent directory, then the group ID of the new file is set to the group ID of the parent directory, otherwise it is set to the effective group ID of the calling process. If the group ID of the new file does not match the effective group ID or one of the supplementary groups IDs, the S_ISGID bit is cleared. The access permission bits of the file mode are set to the value of mode, modified as follows [see creat(2)]: All bits set in the file mode creation mask of the process are cleared [see umask(2)]. The ``save text image after execution bit'' of the mode is cleared [see chmod(2)]. O_TRUNCIf the file exists and is a regular file, and the file is successfully opened O_RDWR or O_WRONLY, its length is truncated to 0 and the mode and owner are unchanged. It will have no effect on FIFO special files or terminal device files. It's effect on other files types is implementation-dependent. The result of using O_TRUNC with O_RDONLY is undefined. O_EXCL If O_EXCL and O_CREAT are set, open will fail if the file exists. The check for the existence of the file and the creation of the file if it does not exist is atomic with respect to other processes executing open naming the same filename in the same directory with O_EXCL and O_CREAT set. O_DIRECT If set, all reads and writes on the resulting file descriptor will be performed directly to or from the user program buffer, provided appropriate size and alignment restrictions are met. Refer to the F_SETFL and F_DIOINFO commands in the fcntl(2) manual entry for information about how to determine the alignment constraints. O_DIRECT is a Silicon Graphics extension and is only supported on local EFS and XFS file systems, and remote BDS file systems. When opening a STREAMS file, oflag may be constructed from O_NDELAY or O_NONBLOCK OR-ed with either O_RDONLY, O_WRONLY , or O_RDWR. Other flag values are not applicable to STREAMS devices and have no effect on them. The values of O_NDELAY and O_NONBLOCK affect the operation of STREAMS drivers and certain system calls [see read(2), getmsg(2), putmsg(2), and write(2)]. For drivers, the implementation of O_NDELAY and O_NONBLOCK is device specific. Each STREAMS device driver may treat these options differently. When open is invoked to open a named stream, and the connld module [see connld(7)] has been pushed on the pipe, open blocks until the server process has issued an I_RECVFD ioctl [see streamio(7)] to receive the file descriptor. If path is a symbolic link and O_CREAT and O_EXCL are set, the link is not followed. The file pointer used to mark the current position within the file is set to the beginning of the file. The new file descriptor is the lowest numbered file descriptor available and is set to remain open across exec system calls [see fcntl(2)]. Certain flag values can be set following open as described in fcntl(2). If O_CREAT is set and the file did not previously exist, upon successful completion open marks for update the st_atime, st_ctime and st_mtime fields of the file and the st_ctime and st_mtime fields of the parent directory. If O_TRUNC is set and the file did previously exist, upon successful completion open marks for update the st_ctime and st_mtime fields of the file. There is a system enforced limit on the number of open file descriptors per process {OPEN_MAX}, whose value is returned by the getdtablesize(2) function. The named file is opened unless one or more of the following are true: EACCES The file does not exist and write permission is denied by the parent directory of the file to be created. EACCES O_CREAT or O_TRUNC is specified and write permission is denied. EACCES A component of the path prefix denies search permission. EACCES The file is a character or block device file and the file system in which it resides has been mounted with the nodev option [see fstab(4)]. EACCES oflag permission is denied for an existing file. EAGAIN The file exists, O_CREAT or O_TRUNC are specified, mandatory file/record locking is set, and there are outstanding record locks on the file [see chmod(2)]. EBUSY path points to a device special file and the device is in the closing state. EDQUOT O_CREAT is specified, the file does not exist, and the directory in which the entry for the new file is being placed cannot be extended either because the user's quota of disk blocks on the file system containing the directory has been exhausted or the user's quota of inodes on the file system on which the file is being created has been exhausted. EEXIST O_CREAT and O_EXCL are set, and the named file exists. EFAULT path points outside the allocated address space of the process. EINTR A signal was caught during the open system call. EINVAL An attempt was made to open a file not in an EFS, XFS or BDS file system with O_DIRECT set. EIO A hangup or error occurred during the open of the STREAMS-based device. EISDIR The named file is a directory and oflag is write or read/write. ELOOP Too many symbolic links were encountered in translating path. EMFILE The process has too many open files [see getrlimit(2)]. ENAMETOOLONG The length of the path argument exceeds {PATH_MAX}, or the length of a path component exceeds {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect. ENFILE The system file table is full. ENODEV path points to a device special file and the device is not in the activated state. ENOENT O_CREAT is not set and the named file does not exist. ENOENT O_CREAT is set and a component of the path prefix does not exist or is the null pathname. ENOMEM The system is unable to allocate a send descriptor. ENOSPC O_CREAT and O_EXCL are set, and the file system is out of inodes or the directory in which the entry for the new file is being placed cannot be extended because there is no space left on the file system containing the directory. ENOSPC O_CREAT is set and the directory that would contain the file cannot be extended. ENOSR Unable to allocate a stream. ENOTDIRA component of the path prefix is not a directory. ENXIO The named file is a character special or block special file, and the device associated with this special file does not exist. ENXIO O_NDELAY or O_NONBLOCK is set, the named file is a FIFO, O_WRONLY is set, and no process has the file open for reading. ENXIO A STREAMS module or driver open routine failed. EOPNOTSUPP An attempt was made to open a socket (not currently supported). EPERM path points to a device special file, the device is in the setup state, and the calling process does not have the P_DEV privilege. ETIMEDOUT The object of the open is located on a remote system which is not available [see intro(2)]. EROFS The named file resides on a read-only file system and either O_WRONLY, O_RDWR, O_CREAT, or O_TRUNC is set in oflag (if the file does not exist). SEE ALSO chmod(2), close(2), creat(2), dup(2), exec(2), fcntl(2), getdtablesize(2), getmsg(2), getrlimit(2), intro(2), lseek(2), putmsg(2), read(2), stat(2), stat(5), umask(2), write(2) DIAGNOSTICS Upon successful completion, the file descriptor is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.