Open System Services System Calls Reference Manual (G06.28+, H06.05+)

open64(2) OSS System Calls Reference Manual
File Status Flags
The file status flags that specify special open processing are:
O_CREAT Create and open the file. If the file exists, this flag has no effect except as noted
under the O_EXCL flag. If the file does not exist, a regular file is created with
these characteristics:
• If access control lists (ACLs) are supported, ACL entries are added to |
the file ACL as described in "ACL Inheritance" in the
acl(5) reference |
page.
• The owner ID of the file is set to the effective user ID of the process.
• The group ID of the file is determined by the value of the S_ISGID flag
in the parent directory. If S_ISGID is set, the group ID of the file is set to
the group ID of the parent directory; otherwise, the group ID of the file is
set to the effective group ID of the calling process. If the file is a Guar-
dian file (that is, within /G), the group ID is set to that of the primary
group of the effective user ID.
• The file permission and attribute bits are set to the value of the mode
parameter, modified as listed:
— The file permission bits are set as described in "ACL Inheri- |
tance" in the acl(5) reference page.
— The set user ID attribute (S_ISUID bit) is cleared.
— The set group ID attribute (S_ISGID bit) is cleared.
If bits other than the file permission and appropriate file-type bits are set
in the mode parameter, errno is set to [EINVAL].
O_EXCL Open the file in exclusive access mode.
If the file exists and the O_EXCL and O_CREAT flags are set, the open fails. If
the file exists and the O_EXCL flag is set and the O_CREAT flag is not set, the
open succeeds.
O_NOCTTY Open the file but not as a controlling terminal. If the path parameter identifies a
terminal device, this flag ensures that the terminal device does not become the
controlling terminal for the process.
When opening a file that is not a terminal device, the O_NOCTTY flag is
ignored.
O_TRUNC Open the file and empty it. If the file does not exist or if the file is not a regular
file, this flag has no effect. If the file exists and is a regular file, and if the file is
successfully opened with either read/write access or write-only access:
• The length of the file is truncated to 0 (zero).
• The owner and group of the file are unchanged.
• The set user ID attribute of the file mode is cleared.
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