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

System Functions (n - p) open(2)
You cannot use the open() function on any other type of Guardian object. An attempt to
open:
— AFormat2file that is larger than approximately 2 gigabytes fails with
errno set |
to [EOVERFLOW].
— A structured file fails with errno set, usually to [EINVAL].
— A file administered through the Storage Management Foundation (SMF) fails
with errno set to [ENOTSUP].
— Any file or device of any other type not described here fails with errno set, usu-
ally to [EINVAL].
An attempt to open a volume, a subvolume, or a process other than a TTY simulation
process (/G/vol, /G/vol/subvol,or/G/process, respectively) fails with errno set to [EIS-
DIR].
• An attempt to open a subvolume with a reserved name beginning with ZYQ (for exam-
ple, /G/vol2/zyq00004) fails with errno set to [EACCES].
• An attempt to open a file within a subvolume with a reserved name beginning with ZYQ
(for example, /G/vol2/zyq00004/z000002x) fails with errno set to [EACCES].
• If the file is not an EDIT file (that is, the file code is not 101), it is opened in shared
exclusion mode.
• If the file is an EDIT file and read-only access is specified, the file is opened in protected
exclusion mode in the Guardian environment.
• If the file is an EDIT file and write access is specified, the call fails with errno set to
[EINVAL].
• The sysconf() function reports the maximum number of opens as the upper limit of
opens per process. The actual limit depends on other factors, such as the size of the pro-
cess file segment (PFS) and the number of existing opens on directories or on files in the
Guardian environment.
• If the open requires file creation, the Guardian file created will be Format 1, odd, unstruc-
tured, and file code 180.
• If the open requires file creation, the file is given access permissions compatible with the
standard security permissions for the Guardian creator access ID (CAID) of the calling
process.
During open() processing, all access permissions are checked. This includes Guardian environ-
ment checks by Guardian standard security mechanisms (and by the Safeguard product) for
Guardian disk file and process access.
Use From the Guardian Environment
A call to the open() function in the Guardian environment requires an OSS pathname and returns
an OSS file-system file descriptor, regardless of the file system containing the file.
The open() function belongs to a set of functions that have these effects when the first of them is
called from the Guardian environment:
• Two Guardian file-system file numbers (not necessarily the next two available) are allo-
cated for the root directory and the current working directory. You cannot close these file
numbers by calling the Guardian FILE_CLOSE_ procedure.
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