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53f2a2eba9
Binary-only compiler and library, plus documentation and include files for compiling new programs.
331 lines
9.0 KiB
Plaintext
Executable File
331 lines
9.0 KiB
Plaintext
Executable File
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OPEN(2V) SYSTEM CALLS OPEN(2V)
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NAME
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open - open or create a file for reading or writing
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SYNOPSIS
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#include <sys/file.h>
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int open(path, flags [ , mode ] )
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char *path;
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int flags, mode;
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DESCRIPTION
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path points to the pathname of a file. open opens the named
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file for reading and/or writing, as specified by the flags
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argument, and returns a descriptor for that file. The flags
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argument may indicate the file is to be created if it does
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not already exist (by specifying the O_CREAT flag), in which
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case the file is created with mode mode as described in
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chmod(2) and modified by the process' umask value (see
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umask(2)). If the path is a null string, the kernel maps
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this null pathname to ., the current directory. flags
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values are constructed by ORing flags from the following
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list (only one of the first three flags below may be used):
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O_RDONLY Open for reading only.
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O_WRONLY Open for writing only.
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O_RDWR Open for reading and writing.
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O_NDELAY When opening a FIFO with O_RDONLY or O_WRONLY set:
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If O_NDELAY is set:
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An open for reading-only will return without
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delay. An open for writing-only will return
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an error if no process currently has the file
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open for reading.
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If O_NDELAY is clear:
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An open for reading-only will block until a
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process opens the file for writing. An open
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for writing-only will block until a process
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opens the file for reading.
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When opening a file associated with a communication
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line:
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If O_NDELAY is set:
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The open will return without waiting for car-
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rier. The first time the process attempts to
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Sun Release 3.2 Last change: 16 July 1986 1
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OPEN(2V) SYSTEM CALLS OPEN(2V)
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perform I/O on the open file it will block
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(not currently implemented).
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If O_NDELAY is clear:
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The open will block until carrier is present.
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O_APPEND If set, the file pointer will be set to the end of
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the file prior to each write.
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O_CREAT If the file exists, this flag has no effect. Oth-
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erwise, the owner ID of the file is set to the
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effective user ID of the process, the group ID of
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the file is set to the group ID of the directory in
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which the file is created, and the low-order 12
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bits of the file mode are set to the value of mode
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modified as follows (see creat(2)):
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All bits set in the file mode creation mask of
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the process are cleared. See umask(2).
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The ``save text image after execution'' bit of
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the mode is cleared. See chmod(2).
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O_TRUNC If the file exists, its length is truncated to 0
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and the mode and owner are unchanged.
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O_EXCL If O_EXCL and O_CREAT are set, open will fail if
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the file exists. This can be used to implement a
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simple exclusive access locking mechanism. If
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O_EXCL is set and the last component of the path-
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name is a symbolic link, the open will fail even if
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the symbolic link points to a non-existent name.
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The file pointer used to mark the current position within
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the file is set to the beginning of the file.
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The new descriptor is set to remain open across execve sys-
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tem calls; see close(2) and fcntl(2).
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There is a system enforced limit on the number of open file
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descriptors per process, whose value is returned by the
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getdtablesize(2) call.
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SYSTEM V DESCRIPTION
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If the O_NDELAY flag is set on an open, that flag is set for
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that file descriptor (see fcntl) and may affect subsequent
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reads and writes. See read(2V) and write(2V).
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RETURN VALUE
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The value -1 is returned if an error occurs, and external
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variable errno is set to indicate the cause of the error.
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Sun Release 3.2 Last change: 16 July 1986 2
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OPEN(2V) SYSTEM CALLS OPEN(2V)
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Otherwise a non-negative numbered file descriptor for the
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new open file is returned.
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ERRORS
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Open fails if:
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ENOTDIR A component of the path prefix of path is not
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a directory.
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EINVAL path contains a character with the high-order
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bit set.
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ENAMETOOLONG The length of a component of path exceeds 255
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characters, or the length of path exceeds
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1023 characters.
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ENOENT O_CREAT is not set and the named file does
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not exist.
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ENOENT A component of the path prefix of path does
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not exist.
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ELOOP Too many symbolic links were encountered in
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translating path.
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EACCES Search permission is denied for a component
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of the path prefix of path.
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EACCES The required permissions (for reading and/or
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writing) are denied for the file named by
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path.
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EACCES The file referred to by path does not exist,
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O_CREAT is specified, and the directory in
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which it is to be created does not permit
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writing.
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EISDIR The named file is a directory, and the argu-
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ments specify it is to be opened for writing.
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ENXIO O_NDELAY is set, the named file is a FIFO,
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O_WRONLY is set, and no process has the file
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open for reading.
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EMFILE The system limit for open file descriptors
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per process has already been reached.
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ENFILE The system file table is full.
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ENOSPC The file does not exist, O_CREAT is speci-
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fied, and the directory in which the entry
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for the new file is being placed cannot be
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Sun Release 3.2 Last change: 16 July 1986 3
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OPEN(2V) SYSTEM CALLS OPEN(2V)
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extended because there is no space left on
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the file system containing the directory.
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ENOSPC The file does not exist, O_CREAT is speci-
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fied, and there are no free inodes on the
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file system on which the file is being
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created.
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EDQUOT The file does not exist, O_CREAT is speci-
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fied, and the directory in which the entry
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for the new file is being placed cannot be
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extended because the user's quota of disk
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blocks on the file system containing the
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directory has been exhausted.
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EDQUOT The file does not exist, O_CREAT is speci-
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fied, and the user's quota of inodes on the
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file system on which the file is being
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created has been exhausted.
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EROFS The named file does not exist, O_CREAT is
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specified, and the file system on which it is
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to be created is a read-only file system.
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EROFS The named file resides on a read-only file
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system, and the file is to be opened for
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writing.
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ENXIO The file is a character special or block spe-
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cial file, and the associated device does not
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exist.
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EINTR A signal was caught during the open system
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call.
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ETXTBSY The file is a pure procedure (shared text)
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file that is being executed and the open call
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requests write access.
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EIO An I/O error occurred while reading from or
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writing to the file system.
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EFAULT path points outside the process's allocated
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address space.
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EEXIST O_EXCL and O_CREAT were both specified and
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the file exists.
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EOPNOTSUPP An attempt was made to open a socket (not
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currently implemented).
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Sun Release 3.2 Last change: 16 July 1986 4
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OPEN(2V) SYSTEM CALLS OPEN(2V)
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SEE ALSO
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chmod(2), close(2), dup(2), fcntl(2), lseek(2), read(2V),
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write(2V), umask(2)
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Sun Release 3.2 Last change: 16 July 1986 5
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