./_Man_Solaris_2.5_html/html2/open.2.html

Manual page for open(2)

open - open for reading or writing

SYNOPSIS

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

int open(const char *path, int oflag, /* mode_t mode */ ...);

MT-LEVEL

Async-Signal-Safe

DESCRIPTION

open() opens a file descriptor for the file with the path name pointed to by path, 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 terminal 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_DSYNC: Write I/O operations on the file descriptor complete as defined by synchronized I/O data integrity completion.
O_RSYNC: Read I/O operations on the file descriptor complete at the same level of integrity as specified by the O_DSYNC and O_SYNC flags. If both O_DSYNC and O_RSYNC are set in oflag, all I/O operations on the file descriptor complete as defined by synchronized I/O data integrity completion. If both O_SYNC and O_RSYNC are set in oflag, all I/O operations on the file descriptor complete as defined by synchronized I/O file integrity completion.
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. Write I/O operations on the file descriptor complete as defined by synchronized I/O file integrity completion.
O_NOCTTY: If set and the file is a terminal, the terminal will not be allocated as the calling process's controlling terminal.
O_CREAT: If 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 ID of the process, the group ID of the file is set to the effective group ID of the process, or if the S_ISGID bit is set in the directory in which the file is being created, the file's group ID is set to the group ID of its parent directory. 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_SYNC Write I/O operations on the file descriptor complete as defined by synchronized I/O file integrity completion (see fcntl.5 definition of O_SYNC .)
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_TRUNC: If the file exists, its length is truncated to 0 and the mode and owner are unchanged. O_TRUNC has no effect on FIFO special files or directories.

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 functions (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.7m has been pushed on the pipe, open() blocks until the server process has issued an I_RECVFD ioctl (see streamio.7i 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 functions (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.

RETURN VALUES

Upon successful completion, the file descriptor is returned. Otherwise, a value of -1 is returned and errno is set to indicate the error.

ERRORS

The named file is opened unless one or more of the following are true: