Open System Services System Calls Reference Manual (G06.25+, H06.03+)

open(2) OSS System Calls Reference Manual
• If the O_NONBLOCK flag is set, the open() function returns without waiting for the
device to be ready or available. Subsequent behavior of the device is device-specific.
When opening a directory, the open fails, and errno is set to [EISDIR], if either of these condi-
tions is true:
• The directory is /E or /G (the Guardian file system) or a directory within /G.
• The directory is not /E or /G and is not within /E or /G, and the file access flag is either
O_WRONLY or O_RDWR.
File Type Flags
The file type flags that can be logically ORed into the value specified in the mode parameter are:
S_IFREG Regular file in the OSS file system or in /G, the Guardian file system.
S_ISVTX Sticky bit; used only for directories (cannot be used for files in /G, the Guardian
file system).
S_NONSTOP Regular file in the OSS file system protected by disk process checkpointing.
(Files in /G cannot have this flag set.)
When set, this flag indicates that return from a write operation does not occur
until both the primary and backup disk processes have the data (thereby protect-
ing the data against a single point of failure).
OSS file-system data caching is disabled for write operations on files for which
this flag is set. Performance is slower than when caching is used, but data
integrity protection increases. Performance is faster than when the O_SYNC
flag in the oflag parameter is used, but data integrity protection is less than that
provided by O_SYNC use.
Opening Guardian Files
If the file is a Guardian file (that is, if it is in the /G file system):
• The file can be opened only if it is:
— A format 1 file on a physical disk volume and one of the following:
— An odd, unstructured Enscribe file. In this case, it is opened as a regular
file with a primary and secondary extent size that is a multiple of 2. If
the extent size is odd, the open fails.
If the unstructured buffer size was not 4096, a successful open makes the
buffer size 4096 (as if the Guardian procedure SETMODE was called for
mode 93 with a parameter value of 4096).
— An EDIT file (file code 101). In this case, it is opened as a regular file
for read-only access.
— A TTY simulation process.
An attempt to open:
— A format 2 file
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