Files and File Structure

If you are looking for information regarding how to use Silo from a parallel application, please See the section on Multi-Block Objects Parallel I/O.

The Silo API is implemented on a number of different low-level drivers. These drivers control the low-level file format Silo generates. For example, Silo can generate PDB (Portable DataBase) and HDF5 formatted files. The specific choice of low-level file format is made at file creation time.

In addition, Silo files can themselves have directories (folders). That is, within a single Silo file, one can create directory hierarchies for storage of various objects. These directory hierarchies are analogous to the Unix file system. Directories serve to divide the name space of a Silo file so the user can organize content within a Silo file in a way that is natural to the application.

Note that the organization of objects into directories within a Silo file may have direct implications for how these collections of objects are presented to users by post-processing tools. For example, except for directories used to store multi-block objects (See Multi-Block Objects Parallel I/O), VisIt will use directories in a Silo file to create submenus within its Graphical User Interface (GUI). If VisIt opens a Silo file with two directories, “foo” and “bar”, and there are various meshes and variables in each of these directories, then many of VisIt’s GUI menus will contain submenus named “foo” and “bar” where the objects found in those directories will be placed in the GUI.

Silo also supports the concept of grabbing the low-level driver. For example, if Silo is using the HDF5 driver, an application can obtain the actual HDF5 file id and then use the native HDF5 API with that file id.

`DBRegisterFileOptionsSet()`

Summary: Register a set of options for advanced control of the low-level I/O driver

C Signature:

int DBRegisterFileOptionsSet(const DBoptlist *opts)

Fortran Signature:
```
int dbregfopts(int optlist_id)
```
Arguments:

Arg name

Description

opts

an options list object obtained from a DBMakeOptlist() call
Returned value:

-1 on failure. Otherwise, the integer index of a registered file options set is returned.

Description:

File options sets are used in concert with the DB_HDF5_OPTS() macro in DBCreate or DBOpen calls to provide advanced and fine-tuned control over the behavior of the underlying driver library and may be needed to affect memory usage and I/O performance as well as vary the behavior of the underlying I/O driver away from its default mode of operation.

A file options set is nothing more than an optlist object (see Optlists), populated with file driver related options. A registered file options set is such an optlist that has been registered with the Silo library via a call to this method, DBRegisterFileOptionsSet. A maximum of 32 registered file options sets are currently permitted. Use DBUnregisterFileOptionsSet to free up a slot in the list of registered file options sets.

Before a specific file options set may be used as part of a DBCreate or DBOpen call, the file options set must be registered with the Silo library. In addition, the associated optlist object should not be freed until after the last call to DBCreate or DBOpen in which it is needed.

Presently, the options sets are defined for the HDF5 driver only. The table below defines and describes the various options. A key option is the selection of the HDF5 Virtual File Driver or VFD. See DBCreate for a description of the available VFDs.

In the table of options below, some options are relevant to only a specific HDF5 VFD. Other options effect the behavior of the HDF5 library as a whole, regardless of which underlying VFD is used. This difference is notated in the scope column.

All of the options described here relate to options documented in the HDF5 library’s file access property lists.

Note that all option names listed in left-most column of the table below have had their prefix “DBOPT_H5_” removed to save space in the table. So, for example, the real name of the CORE_ALLOC_INC option is DBOPT_H5_CORE_ALLOC_INC.

`DBOPT_H5_`…	Type	Meaning	Default
`VFD`	`int`	Specifies which Virtual File Driver (VFD) the HDF5 library should use. Set the integer value for this option to one of the following values. `DB_H5VFD_DEFAULT`, (use HDF5 default driver) `DB_H5VFD_SEC2` (use HDF5 sec2 driver) `DB_H5VFD_STDIO`, (use HDF5 stdio driver) `DB_H5VFD_CORE`, (use HDF5 core driver) `DB_H5VFD_LOG`, (use HDF5 log river) `DB_H5VFD_SPLIT`, (use HDF5 split driver) `DB_H5VFD_DIRECT`, (use HDF5 direct i/o driver) `DB_H5VFD_FAMILY`, (use HDF5 family driver) `DB_H5VFD_MPIO`, (use HDF5 mpi-io driver) `DB_H5VFD_MPIP`, (use HDF5 mpi posix driver) `DB_H5VFD_SILO`, (use `SILO` BG/Q driver) `DB_H5VFD_FIC` (use `SILO` file in core driver). Many of the reamining options described in this table apply to only certain of the above VFDs.
`RAW_FILE_OPTS`	`int`	Applies only for the split VFD. Specifies a file options set to use for the raw data file. May be any value returned from a call to DBRegisterFileOptionsSet() or can be any one of the following pre-defined file options sets… `DB_FILE_OPTS_H5_DEFAULT_`… DEFAULT, SEC2, STDIO, CORE, LOG, SPLIT, DIRECT, FAMILY, MPIO, MPIP, `SILO`. See HDF5 reference manual for H5Pset_fapl_split
`RAW_EXTENSION`	`char*`	Applies only for the split VFD. Specifies the file extension/naming convention for raw data file. If the string contains a ‘%s’ printf-like conversion specifier, that will be replaced with the name of the file passed in the DBCreate/DBOpen call. If the string does not contain a ‘%s’ printf-like conversion specifier, it is treated as an ‘extension’ which is appended to the name of the file passed in DBCreate/DBopen call. See HDF5 reference manual for H5Pset_fapl_split	“-raw”
`META_FILE_OPTS`	`int`	Same as `DBOPT_H5_RAW_FILE_OPTS`, above, except for meta data file. See HDF5 reference manual for H5Pset_fapl_split.
`META_EXTENSION`		Same as `DBOPT_H5_RAW_EXTENSION` above, except for meta data file. See HDF5 reference manual for H5Pset_fapl_split.	“”
`CORE_ALLOC_INC`	`int`	Applies only for core VFD. Specifies allocation increment. See HDF5 reference manual for H5Pset_fapl_core.	(1<<20)
`CORE_NO_BACK_STORE`	`int`	Applies only for core VFD. Specifies whether or not to store the file on close. See HDF5 reference manual for H5Pset_fapl_core.	FALSE
`LOG_NAME`	`char*`	Applies only for the log VFD. This is primarily a debugging feature. Specifies name of the file to which loggin data shall be stored. See HDF5 reference manual for H5Pset_fapl_log.	“log.out”
`LOG_BUF_SIZE`	`int`	Applies only for the log VFD. This is primarily a debugging feature. Specifies size of the buffer to which byte-for-byte HDF5 data type information is written. See HDF5 refrence manual for H5Pset_fapl_log.	0
`META_BLOCK_SIZE`	`int`	Applies the the HDF5 library as a whole (e.g. globally). Specifies the size of memory allocations the library should use when allocating meta data. See HDF5 reference manual for H5Pset_meta_block_size.	0
`SMALL_RAW_SIZE`	`int`	Applies to the HDF5 library as a whole (e.g. globally). Specifies a threshold below which allocations for raw data are aggregated into larger blocks within HDF5. This can improve I/O performance by reducing number of small I/O requests. Note, however, that with a block-oriented VFD such as the Silo specific VFD, this parameter must be set to be consistent with block size of the VFD. See HDF5 reference manual for H5Pset_small_data_block_size.	0
`ALIGN_MIN`	`int`	Applies to the HDF5 library as a whole. Specified a size threshold above which all datasets are aligned in the file using the value specified in `ALIGN_VAL`. See HDF5 reference manual for H5Pset_alignment.	0
`ALIGN_VAL`	`int`	The alignment to be applied to datasets of size greater than `ALIGN_MIN`. See HDF5 reference manual for H5Pset_alignment.	0
`DIRECT_MEM_ALIGN`	`int`	Applies only to the direct VFD. Specifies the alignment option. See HDF5 reference manual for H5Pset_fapl_direct.	0
`DIRECT_BLOCK_SIZE`	`int`	Applies only to the direct VFD. Specifies the block size the underlying file system is using. See HDF5 reference manual for H5Pset_fapl_direct.
`DIRECT_BUF_SIZE`		Applies only to the direct VFD. Specifies a copy buffer size. See HDF5 reference manual for H5Pset_fapl_direct.
`MPIO_COMM`
`MPIO_INFO`
`MPIP_NO_GPFS_HINTS`
`SIEVE_BUF_SIZE`	`int`	HDF5 sieve buf size. Only relevant if using either compression and/or checksumming. See HDF5 reference manual for H5Pset_sieve_buf_size.
`CACHE_NELMTS`	`int`	HDF5 raw data chunk cache parameters. Only relevant if using either compression and/or checksumming. See HDF5 reference manual for H5Pset_cache.
`CACHE_NBYTES`		HDF5 raw data chunk cache parameters. Only relevant if using either compression and/or checksumming. See HDF5 reference manual for H5Pset_cache.
`CACHE_POLICY`		HDF5 raw data chunk cache parameters. Only relevant if using either compression and/or checksumming. See HDF5 reference manual for H5Pset_cache.
`FAM_SIZE`	`int`	Size option for family VFD. See HDF5 reference manual for H5Pset_fapl_family. The family `VFD` is useful for handling files that would otherwise be larger than 2Gigabytes on file systems that support a maximum file size of 2Gigabytes.
`FAM_FILE_OPTS`	`int`	VFD options for each file in family VFD. See HDF5 reference manual for H5Pset_fapl_family. The family VFD is useful for handling files that would otherwise be larger than 2Gigabytes on file systems that support a maximum file size of 2Gigabytes.
`USER_DRIVER_ID`	`int`	Specify some user-defined VFD. Permtis application to specify any user-defined VFD. See HDF5 reference manual for H5Pset_driver.
`USER_DRIVER_INFO`		Specify user-defined VFD information struct. Permtis application to specify any user-defined VFD. See HDF5 reference manual for H5Pset_driver.
`SILO_BLOCK_SIZE`	`int`	Block size option for Silo VFD. All I/O requests to/from disk will occur in blocks of this size.	(1<<16)
`SILO_BLOCK_COUNT`	`int`	Block count option for Silo VFD. This is the maximum number of blocks the Silo VFD will maintain in memory at any one time.	32
`SILO_LOG_STATS`	`int`	Flag to indicate if Silo VFD should gather I/O performance statistics. This is primarily for debugging and performance tuning of the Silo VFD.	0
`SILO_USE_DIRECT`	`int`	Flag to indicate if Silo VFD should attempt to use direct I/O. Tells the Silo VFD to use direct I/O where it can. Note, if it cannot, this option will be siliently ignored.	0
`FIC_BUF`	`void*`	The buffer of bytes to be used as the “file in core” to be opened in a `DBOpen()` call.	none
`FIC_SIZE`	`int`	Size of the buffer of bytes to be used as the “file in core” to be opened in a `DBOpen()` call.	none

`DBUnregisterFileOptionsSet()`

Summary: Unregister a registered file options set

C Signature:

int DBUnregisterFileOptionsSet(int opts_set_id)

Fortran Signature:
```
int dbunregfopts(int optlist_id)
```
Arguments:

Arg name

Description

opts_set_id

The identifer (obtained from a previous call to DBRegisterFileOptionsSet()) of a file options set to unregister.
Returned value:

Zero on success. -1 on failure.
Description:

Unregister a specific file options set identified by opts_set_id.

`DBUnregisterAllFileOptionsSets()`

Summary: Unregister all file options sets
C Signature:
```
int DBUnregisterAllFileOptionsSets()
```
Fortran Signature:
```
int dbunregafopts()
```
Arguments:

None
Returned value:

Zero on success, -1 on failure.
Description:

Unregister all file options sets.

`DBSetUnknownDriverPriorities()`

Summary: Set driver priorities for opening files with the DB_UNKNOWN driver.

C Signature:

static const int *DBSetUnknownDriverPriorities(int *driver_ids)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

driver_ids

A -1 terminated list of driver ids such as DB_HDF5, DB_PDB, DB_HDF5_CORE, or any driver id constructed with the DB_HDF5_OPTS() macro.
Returned value:

The previous unknown driver prioritizatin as a -1 terminated array of integer values. The caller should NOT free the returned value.
Description:

When opening files with DB_UNKNOWN driver, Silo iterates over drivers, trying each until it successfuly opens a file.

This call can be used to affect the order in which driver ids are attempted and can improve behavior and performance for opening files using DB_UNKNOWN driver.

If any of the driver ids specified in driver_ids is constructed using the DB_HDF5_OPTS() macro, then the associated file options set must be registered with the Silo library.

`DBGetUnknownDriverPriorities()`

Summary: Return the currently defined ordering of drivers the DB_UNKNOWN driver will attempt.

C Signature:

static const int *DBGetUnknownDriverPriorities(void)

Fortran Signature:
```
None
```
Description:

Returns a -1 terminated list of integer driver ids indicating the prioritzation of drivers used by the DB_UNKNOWN driver. The caller should NOT free the returned value.

`DBCreate()`

Summary: Create a Silo output file.

C Signature:

DBfile *DBCreate (char *pathname, int mode, int target,
    char *fileinfo, int filetype)

Fortran Signature:

integer function dbcreate(pathname, lpathname, mode, target,
   	fileinfo, lfileinfo, filetype, dbid)

returns the newly created database file handle in dbid.

Arguments:

Arg name	Description
`pathname`	Path name of file to create. This can be either an absolute or relative path.
`mode`	Creation `mode`. Pass `DB_CLOBBER` or `DB_NOCLOBBER`, optionally OR’d with `DB_PERF_OVER_COMPAT` or `DB_COMPAT_OVER_PERF` (see `DBSetCompatibilityMode`
`target`	Destination file format. In the distant past, this option was used to target binary numeric formats in the file to a specific host CPU architecture (such as Sun or Sgi or Cray). More recently, this argument has become less relevant and should most likely always be set to `DB_LOCAL`.
`fileinfo`	Character string containing descriptive information about the file’s contents. This information is usually printed by applications when this file is opened. If no such information is needed, pass `NULL` for this argument.
`filetype`	Destination file type. Applications typically use one of either `DB_PDB`, which will create PDB files, or `DB_HDF5`, which will create HDF5 files. Other options include `DB_PDBP`, `DB_HDF5_SEC2`, `DB_HDF5_STDIO`, `DB_HDF5_CORE`, `DB_HDF5_SPLIT` or `DB_FILE_OPTS(optlist_id)` where `optlist_id` is a registered file options set. For a description of the meaning of these options as well as many other advanced features and control of underlying I/O behavior, see DBRegisterFileOptionsSet.

Returned value:

DBCreate returns a DBfile pointer on success and NULL on failure. If the pathname argument contains a path components (e.g. foo/bar/baz/file.silo), note that DBCreate creates only the file part of the path. The containing directories (folders) must already exist and be writeable.
Description:

The DBCreate function creates a Silo file and initializes it for writing data.

Silo supports two underlying drivers for storing named arrays and objects of machine independent data. One is called the Portable DataBase Library (PDBLib or just PDB), and the other is Hierarchical Data Format, Version 5 (HDF5), http://www.hdfgroup.org/HDF5.

When Silo is configured with the --with-pdb-proper=<path-to-PACT-PDB> option, the Silo library supports both the PDB driver that is built-in to Silo (which is actually an ancient version of PACT’s PDB referred to internally as PDB Lite) identified with a filetype of DB_PDB and a second variant of the PDB driver using a PACT installation (specified when Silo was configured) with a filetype of DB_PDBP (Note the trailing P for PDB Proper). PDB Proper is known to give far superior performance than PDB Lite on BG/P and BG/L class systems and so is recommended when using PDB driver on such systems.

For the HDF5 library, there are many more available options for fine tuned control of the underlying I/O through the use of HDF5’s Virtual File Drivers (VFDs). For example, HDF5’s sec2 VFD uses Unix Manual Section 2 I/O routines (e.g. create/open/read/write/close) while the stdio VFD uses Standard I/O routines (e.g. fcreate/fopen/fread/fwrite/fclose).

Depending on the circumstances, the choice of VFD can have a profound impact on actual I/O performance. For example, on BlueGene systems the customized Silo block-based VFD (introduced to the Silo library in Version 4.8) has demonstrated excellent performance compared to the default HDF5 VFD; sec2. The remaining paragraphs describe each of the available Virtual File Drivers as well as parameters that govern their behavior.

DB_HDF5
From among the several VFDs that come pre-packaged with the HDF5 library, this driver type uses whatever the HDF5 library defines as the default VFD. On non-Windows platforms, this is the Section 2 (see below) VFD. On Windows platforms, it is a Windows specific VFD.

DB_HDF5_SEC2
Uses the I/O system interface defined in section 2 of the Unix manual. That is create, open, read, write, close. This is a VFD that comes pre-packaged with the HDF5 library. It does little to no optimization of I/O requests. For example, two I/O requests that abutt in file address space wind up being issued through the section 2 I/O routines as independent requests. This can be disasterous for high latency file systems such as might be available on BlueGene class systems.

DB_HDF5_STDIO
Uses the Standard I/O system interface defined in Section 3 of the Unix manual. That is fcreate, fopen, fread, fwrite, fclose. This is a VFD that comes pre-packaged with the HDF5 library. It does little to no optimization of I/O requests. However, since it uses the stdio routines, it does benefit from whatever default buffering the implementation of the stdio interface on the given platform provides. Because section 2 routines are unbuffered, the sec2 VFD typically performs better when there are fewer, larger I/O requests while the stdio VFD performs better when there are more, smaller requests. Unfortunately, the metric for what constitutes a “small” or “large” request is system dependent. So, it helps to experiment with the different VFDs for the HDF5 driver by running some typically sized use cases. Some results on the Luster file system for tiny I/O requests (100’s of bytes) showed that the stdio VFD can perform 100x or more better than the section 2. So, it pays to spend some time experimenting with this [Note: In future, it should be possible to manipulate the buffer used for a given Silo file opened via the stdio VFD as one would ordinarily do via such stdio calls as setvbuf(). However, due to limitations in the current implementation, that is not yet possible. When and if that becomes possible, to use something other than non-default stdio buffering, the Silo client will have to create and register an appropriate file options set.

DB_HDF5_CORE
Uses a memory buffer for the file with the option of either writing the resultant buffer to disk or not. Conceptually, this VFD behaves more or less like a ramdisk. This is a VFD that comes pre-packaged with the HDF5 library. I/O performance is optimal in the sense that only a single I/O request for the entire file is issued to the underlying file system. However, this optimality comes at the expense of memory. The entire file must be capable of residing in memory. In addition, releases of HDF5 library prior to 1.8.2 support the core VFD only when creating a new file and not when open an existing file. Two parameters govern behavior of the core VFD. The allocation increment specifies the amount of memory the core VFD allocates, each time it needs to increase the buffer size to accomodate the (possibly growing) file. The backing store indicates whether the buffer should be saved to disk (if it has been changed) upon close. By default, using DB_HDF5_CORE as the driver type results in an allocation incriment of 1 Megabyte and a backing store option of TRUE, meaning it will store the file to disk upon close. To specify parameters other than these default values, the Silo client will have to create and register an appropriate file options set, see DBRegisterFileOptionsSet.

DB_HDF5_SPLIT
Splits HDF5 I/O operations across two VFDs. One VFD is used for all raw data while the other VFD is used for everything else (e.g. meta data). For example, in Silo’s DBPutPointvar() call, the data the caller passes in the vars argument is raw data. Everything else including the object’s name, number of points, datatype, optlist options, etc. including all underlying HDF5 metadata gets treated as meta data. This is a VFD that comes pre-packaged with the HDF5 library. It results in two files being produced; one for the raw data and one for the meta data. The reason this can be a benefit is that tiny bits of metadata intermingling with large raw data operations can degrade performance overall. Separating the datastreams can have a profound impact on performance at the expense of two files being produced. Four parameters govern the behavior of the split VFD. These are the VFD and filename extension for the raw and meta data, respectively. By default, using DB_HDF5_SPLIT as the driver type results in Silo using sec2 and "-raw" as the VFD and filename extension for raw data and core (default params) and "" (empty string) as the VFD and extension for meta data. To specify parameters other than these default values, the Silo client will have to create and register an appropriate file options set, see DBRegisterFileOptionsSet.

DB_HDF5_FAMILY
Allows for the management of files larger than 2³² bytes on 32-bit systems. The virtual file is decomposed into real files of size small enough to be managed on 32-bit systems. This is a VFD that comes pre-packaged with the HDF5 library. Two parameters govern the behavior of the family VFD. The size of each file in a family of files and the VFD used for the individual files. By default, using DB_HDF5_FAMILY as the driver type results in Silo using a size of 1 Gigabyte (2³²) and the default VFD for the individual files. To specify parameters other than these default values, the Silo client will have to create and register an appropriate file options set, see DBRegisterFileOptionsSet.

DB_HDF5_LOG
While doing the I/O for HDF5 data, also collects detailed information regarding VFD calls issued by the HDF5 library. The logging VFD writes detailed information regarding VFD operations to a logfile. This is a VFD that comes pre-packaged with the HDF5 library. However, the logging VFD is a different code base than any other VFD that comes pre-packaged with HDF5. So, while the logging information it produces is representative of the VFD calls made by HDF5 library to the VFD interface, it is not representative of the actual I/O requests made by the sec2 or stdio or other VFDs. Behavior of the logging VFD is governed by 3 parameters; the name of the file to which log information is written, a set of flags which are or’d together to specify the types of operations and information logged and, optionally, a buffer (which must be at least as large as the actual file being written) which serves to map the kind of HDF5 data (there are about 8 different kinds) stores at each byte in the file. By default, using DB_HDF5_LOG as the driver type results in Silo using a logfile name of “silo_hdf5_log.out”, flags of H5FD_LOG_LOC_IO|H5FD_LOG_NUM_IO|H5FD_LOG_TIME_IO|H5FD_LOG_ALLOC and a NULL buffer for the mapping information. To specify parameters other than these default values, the Silo client will have to create and register an appropriate file options set, see DBRegisterFileOptionsSet.

Users interested in this VFD should consult HDF5’s reference manual for the meaning of the flags as well as how to interepret logging VFD output.

DB_HDF5_DIRECT
On systems that support the O_DIRECT flag in section 2 create/open calls, this VFD will use direct I/O. This VFD comes pre-packaged with the HDF5 library. Most systems (both the system interfaces implementations for section 2 I/O as well as underlying file systems) do a lot of work to buffer and cache data to improve I/O performance. In some cases, however, this extra work can actually get in the way of good performance, particularly when the I/O operations are streaming like and large. Three parameters govern the behavior of the direct VFD. The alignment specifies memory alignment requirement of raw data buffers. That generally means that posix_memalign should be used to allocate any buffers you use to hold raw data passed in calls to the Silo library. The block size indicates the underlying file system block size and the copy buffer size gives the HDF5 library some additional flexibility in dealing with unaligned requests. Few systems support the O_DIRECT flag and so this VFD is not often available in practice. However, when it is, using DB_HDF5_DIRECT as the driver type results in Silo using an alignment of 4 kilobytes (2¹²), an alignment equal to the block size and a copy buffer size equal to 256 times the blocksize.

DB_HDF5_SILO
This is a custom VFD designed specifically to address some of the performance shortcommings of VFDs that come pre-packaged with the HDF5 library. The silo VFD is a very, very simple, block-based VFD. It decomposes the file into blocks, keeps some number of blocks in memory at any one time and issues I/O requests only in whole blocks using section 2 I/O routines. In addition, it sets up some parameters that control HDF5 library’s allocation of meta data and raw data such that each block winds up consisting primirily of either raw or meta data but not both. It also disables meta data caching in HDF5 to reduce memory consumption of the HDF5 library to the bare minimum as there is no need for HDF5 to maintain cached metadata if it resides in blocks kept in memory in the VFD. This is a suitable VFD for most scientific computing applications that are dumping either post-processing or restart files as applications that do that tend to open the file, write a bunch of stuff from start to finish and close it or read a bunch of stuff from start to finish and close it. Two parameters govern the behavior of the silo VFD; the block size and the block count. The block size determines the size of individual blocks. All I/O requests will be issued in whole blocks. The block count determines the number of blocks the silo VFD is permitted to keep in memory at any one time. On BG/P class systems, good values are 1 Megabyte (2²⁰) block size and block count of 16 or 32. By default, the silo VFD uses a block size of 16 Kilobytes (2¹⁴) and a block count also of 16. To specify parameters other than these default values, the Silo client will have to create and register an appropriate file options set, see DBRegisterFileOptionsSet.

DB_HDF5_MPIO and DB_HDF5_MPIOP
These have been removed from Silo as of version 4.10.3.

In Fortran, an integer represent the file’s id is returned. That integer is then used as the database file id in all functions to read and write data from the file.

Note that regardless of what type of file is created, it can still be read on any machine.

See notes in the documentation on DBOpen regarding use of the DB_UNKNOWN driver type.

`DBOpen()`

Summary: Open an existing Silo file.

C Signature:

DBfile *DBOpen (char *name, int type, int mode)

Fortran Signature:

integer function dbopen(name, lname, type, mode,
   dbid)

returns database file handle in dbid.

Arguments:

Arg name	Description
`name`	Name of the file to open. Can be either an absolute or relative path.
`type`	The `type` of file to open. One of the predefined types, typically `DB_UNKNOWN`, `DB_PDB`, or `DB_HDF5`. However, there are other options as well as subtle but important issues in using them. So, read description, below for more details.
`mode`	The `mode` of the file to open. Pass `DB_READ` or `DB_APPEND`. Optionally, `DB_APPEND` can be OR’d with `DB_PERF_OVER_COMPAT` or `DB_COMPAT_OVER_PERF` (see `DBSetCompatibilityMode`. OR’ing of `DB_READ` with compatibility mode flags is not allowed.

Returned value:

DBOpen returns a DBfile pointer on success and a NULL on failure.
Description:

The DBOpen function opens an existing Silo file. If the file type passed here is DB_UNKNOWN, Silo will attempt to guess at the file type by iterating through the known types attempting to open the file with each driver until it succeeds. This iteration may incur a small performance penalty. In addition, use of DB_UNKNOWN can have other undesireable behavior described below. So, if at all possible, it is best to open using a specific type. See DBGetDriverTypeFromPath() for a function that uses cheap heuristics to determine the driver type given a candiate filename.

When writing general purpose code to read Silo files and you cannot know for certain ahead of time what the correct driver to use is, there are a few options.

First, you can iterate over the available driver ids, calling DBOpen() using each one until one of them succeds. But, that is exactly what the DB_UNKNOWN driver does so there is no need for a Silo client to have to write that code. In addition, if you have a specific preference of order of drivers, you can use DBSetUnknownDriverPriorities() to specify that ordering.

Undesireable behavior with DB_UNKNOWN can occur when the specified file can be successfully opened using multiple available drivers and/or file options sets and it succceds with one or one using options the caller neither expected or intended and/or which offers poorer performance. See DBSetUnknownDriverPriorities for a way to specify the order of drivers tried by the DB_UNKNOWN driver.

Indeed, in order to use a specific VFD (see DBCreate) in HDF5, it is necessary to pass the specific DB_HDF5_XXX argument in this call or to set the unknown driver priorities such that whatever specific HDF5 VFD(s) are desired are tried first before falling back to other, perhaps less desirable ones.

The mode parameter allows a user to append to an existing Silo file. If a file is opened with a mode of DB_APPEND, the file will support write operations as well as read operations.

`DBFlush()`

Summary:
C Signature:
```
int DBFlush(DBfile *dbile)
```
Fortran Signature:
```
None
```
Arguments:

Arg name

Description

dbfile

the file to be flushed
Returned value:

Zero on success; -1 on failure.
Description:

Flush any changes to a file to disk without having to actually close the file.

`DBClose()`

Summary: Close a Silo database.
C Signature:
```
int DBClose (DBfile *dbfile)
```
Fortran Signature:
```
integer function dbclose(dbid)
```
Arguments:

Arg name

Description

dbfile

Database file pointer.
Returned value:

DBClose returns zero on success and -1 on failure.
Description:

The DBClose function closes a Silo database.

Note: For files produced by the HDF5 driver, the occasional bug in the Silo library can lead to situations where DBClose() might fail to actually close the file. There is logic in Silo to try to detect this if it is happening and then issue a warning or error message. However, a caller may not be paying attention to Silo function return values or error messages.

`DBGetToc()`

Summary: Get the table of contents of a Silo database.
C Signature:
```
DBtoc *DBGetToc (DBfile *dbfile)
```
Fortran Signature:
```
None
```
Arguments:

Arg name

Description

dbfile

Database file pointer.
Returned value:

DBGetToc returns a pointer to a DBtoc structure on success and NULL on error.
Description:

The DBGetToc function returns a pointer to a DBtoc structure, which contains the names of the various Silo object contained in the Silo database. The returned pointer points into Silo private space and must not be modified or freed. Also, calls to DBSetDir will free the DBtoc structure, invalidating the pointer returned previously by DBGetToc.

File-level properties

There are a number of methods that control overall behavior either globally to the whole library or for a specific file. These are all documented in the Global Library Behavior section.

`DBFileName()`

Summary:
C Signature:
```
char const *DBFileName(DBfile *dbfile)
```
Fortran Signature:
```
None
```
Arguments:

Arg name

Description

dbfile

the Silo database file for which the name is to be queried.
Returned value:

Always succeeds. May return string containing “unknown”.

`DBFileVersion()`

Summary: Version of the Silo library used to create the specified file

C Signature:

char const *DBFileVersion(DBfile *dbfile)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

dbfile

Database file handle
Returned value:

A character string representation of the version number of the Silo library that was used to create the Silo file. The caller should not free the returned string.
Description:

Note, that this is distinct from (e.g. can be the same or different from) the version of the Silo library returned by the DBVersion() function.

DBFileVersion(), here, returns the version of the Silo library that was used when DBCreate() was called on the specified file. DBVersion() returns the version of the Silo library the executable is currently linked with.

Most often, these two will be the same. But, not always. Also note that although is possible that a single Silo file may have contents created within it from multiple versions of the Silo library, a call to this function will return only the version that was in use when DBCreate() was called; that is when the file was first created.

`DBFileVersionDigits()`

Summary: Return integer digits of file version number

C Signature:

int DBFileVersionDigits(const DBfile *dbfile,
    int *maj, int *min, int *pat, int *pre)

Fortran Signature:
```
None
```

Arguments:

Arg name	Description
`dbfile`	Silo database file handle
`maj`	Pointer to returned major version digit
`min`	Pointer to returned minor version digit
`pat`	Pointer to returned patch version digit
`pre`	Pointer to returned pre-release version digit (if any)

Returned value:

Zero on success. Negative value on failure.

`DBFileVersionGE()`

Summary: Greater than or equal comparison for version of the Silo library a given file was created with

C Signature:

int DBFileVersionGE(DBfile *dbfile, int Maj, int Min, int Pat)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

dbfile

Database file handle

Maj

Integer major version number

Min

Integer minor version number

Pat

Integer patch version number
Returned value:

One (1) if the version number of the library used to create the specified file is greater than or equal to the version number specified by Maj, Min, Pat arguments, zero (0) otherwise. A negative value is returned if a failure occurs.

`DBVersionGEFileVersion()`

Summary: Compare library version with file version

C Signature:

int DBVersionGEFileVersion(const DBfile *dbfile)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

dbfile

Silo database file handle obtained with a call to DBOpen
Returned value:

Non-zero if the library version is greater than or equal to the file version. Zero otherwise.

`DBSortObjectsByOffset()`

Summary: Sort list of object names by order of offset in the file

C Signature:

int DBSortObjectsByOffset(DBfile *, int nobjs,
    const char *const *const obj_names, int *ordering)

Fortran Signature:
```
None
```

Arguments:

Arg name	Description
`DBfile`	Database file pointer.
`nobjs`	Number of object names in obj_names.
`ordering`	Returned integer array of relative order of occurence in the file of each object. For example, if ordering[i]==k, that means the object whose name is obj_names[i] occurs kth when the objects are ordered according to offset at which they exist in the file.

Returned value:

0 on succes; -1 on failure. The only possible reason for failure is if the HDF5 driver is being used to read the file and Silo is not compiled with HDF5 version 1.8 or later.
Description:

The intention of this function is to permit applications reading Silo files to order their reads in such a way that objects are read in the order in which they occur in the file. This can have a postive impact on I/O performance, particularly using a block-oriented VFD such as the Silo VFD as it can reduce and/or eliminate unnecessary block pre-emption. The degree to which ordering reads effects performance is not yet known.

`DBMkDir()`

Summary: Create a new directory in a Silo file.

C Signature:

int DBMkDir (DBfile *dbfile, char const *dirname)

Fortran Signature:

integer function dbmkdir(dbid, dirname, ldirname, status)

Arguments:

Arg name

Description

dbfile

Database file pointer.

dirname

Name of the directory to create.
Returned value:

DBMkDir returns zero on success and -1 on failure.
Description:

The DBMkDir function creates a new directory in the Silo file as a child of the current directory (see DBSetDir). The directory name may be an absolute path name similar to "/dir/subdir", or may be a relative path name similar to "../../dir/subdir".

`DBMkDirP()`

Summary: Create a new directory, as well as any necessary intervening directories, in a Silo file.

C Signature:

int DBMkDirP(DBfile *dbfile, char const *dirname)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

dbfile

Database file pointer.

dirname

Name of the directory to create.
Returned value:

Returns zero on success and -1 on failure.
Description:

The DBMkDirP function creates a new directory in the Silo file including making any necessary intervening directories. This is the Silo equivalent of Unix’ mkdir -p. The directory name may be an absolute path name similar to "/dir/subdir", or may be a relative path name similar to "../../dir/subdir".

`DBSetDir()`

Summary: Set the current directory within the Silo database.

C Signature:

int DBSetDir (DBfile *dbfile, char const *pathname)

Fortran Signature:

integer function dbsetdir(dbid, pathname, lpathname)

Arguments:

Arg name

Description

dbfile

Database file pointer.

pathname

Path name of the directory. This can be either an absolute or relative path name.
Returned value:

DBSetDir returns zero on success and -1 on failure.
Description:

The DBSetDir function sets the current directory within the given Silo database. Also, calls to DBSetDir will free the DBtoc structure, invalidating the pointer returned previously by DBGetToc. DBGetToc must be called again in order to obtain a pointer to the new directory’s DBtoc structure.

`DBGetDir()`

Summary: Get the name of the current directory.

C Signature:

int DBGetDir (DBfile *dbfile, char *dirname)

Fortran Signature:
```
None
```

Arguments:

Arg name	Description
`dbfile`	Database file pointer.
`dirname`	Returned current directory name. The caller must allocate space for the returned name. The maximum space used is `256` characters, including the `NULL` terminator.

Returned value:

DBGetDir returns zero on success and -1 on failure.
Description:

The DBGetDir function returns the name of the current directory.

`DBCpDir()`

Summary: Copy a directory hierarchy from one Silo file to another.

C Signature:

int DBCpDir(DBfile *srcFile, const char *srcDir,
    DBfile *dstFile, const char *dstDir)

Fortran Signature:
```
None
```

Arguments:

Arg name	Description
`srcFile`	Source database file pointer.
`srcDir`	Name of the directory within the source database file to copy.
`dstFile`	Destination database file pointer.
`dstDir`	Name of the top-level directory in the destination file. If an absolute path is given, then all components of the path except the last must already exist. Otherwise, the new directory is created relative to the current working directory in the file.

Returned value:

DBCpDir returns 0 on success, -1 on failure
Description:

DBCpDir copies an entire directory hierarchy from one Silo file to another.

Note that this function is available only on the HDF5 driver and only if the Silo library has been compiled with HDF5 version 1.8 or later. This is because the implementation exploits functionality available only in versions of HDF5 1.8 and later.

`DBCpListedObjects()`

Summary: Copy lists of objects from one Silo database to another

C Signature:

int DBCpListedObjects(int nobjs,
    DBfile *srcDb, char const * const *srcObjList,
    DBfile *dstDb, char const * const *dstObjList)

Fortran Signature:
```
None
```

Arguments:

Arg name	Description
`nobjs`	The number of objects to be copied (e.g. number of strings in srcObjList)
`srcDb`	The Silo database to be used as the source of the copies
`srcObjList`	An array of nobj strings of the (path) names of objects to be copied. See description for interpretation of relative path names.
`dstDB`	The Silo database to be used as the destination of the copies.
`dstObjList`	[Optional] An optional array of nobj strings of the (path) names where the objects are to be copied in dstDb. If any entry in `dstObjList` is `NULL` or is a string of zero length, this indicates that object in the dstDb will have the same (path) name as the corresponding object (path) name given in `srcObjList`. If the entire `dstObjList` is `NULL`, then this is true for all objects. See description for interpretation of relative (path) names.

Returned value:

Returns 0 on success, -1 on failure
Description:

Note that this function is available only if both Silo databases are from the HDF5 driver and only if the Silo library has been compiled with HDF5 version 1.8 or later. This is because the implementation exploits functionality available only in versions of HDF5 1.8 and later.

Directories required in the destination database to satisfy the path names given in the

dstObjList are created as necessary. There is no need for the caller to pre-create any directories in the destination database.

Relative path names in the srcObjList are interpreted relative to the source database’s current working directory. Likewise, relative path names in the dstObjectList are interpreted relative to the destination databases’s current working directory. Of course, if objects are specified using absolute path names, then copies will occur regardless of source or destination databases’s current working directory.

If an object specified in the srcObjList is itself a directory, then the entire directory tree rooted at that name will be copied to the destination database.

If dstObjList is NULL, then it is assumed that all the objects to be copied will be copied to paths in the destination database that are intended to be the same as those in srcObjList. If dstObjList is non-NULL, but any given entry is either NULL or a string of zero length, than that object’s destination name will be assumed the same as its equivalent srcObjList entry. Note, when using NULLs relative paths in srcObjList will appear in destination databases relative to the destination database’s current working directory.

If dstObjList[i] ends in a ‘/’ character or identifies a directory that existed in the destination database either before DBCpListedObjects was called or that was created on behalf of a preceding object copy within the execution of DBCpListedObjects, then the source object will be copied to that directory with its original (source) name. This is equivalent to the behavior of the file system command cp foo /gorfo/bar/ or cp foo /gorfo/bar when bar exists as a directory.

Finally, users should be aware that if there are numeric architecture differences between the host where the source object data was produced and the host where this copy operation is being performed, then in all likelihood the destination copies of any floating point data may not match bit-for-bit with the source data. This is because data conversion may have been involved in the process of reading the data into memory and writing the copy back out.

For example, suppose we have two databases…
1. DBfile *dbfile (“dir.silo”) containing…
  - /ucd_dir/ucdmesh (ucd mesh object)
  - /tri_dir/trimesh (ucd mesh object) <– current working directory
  - /quad_dir/quadmesh (quad mesh object)
2. DBfile *dbfile2 (“dir2.silo”) containing…
  - /tmp <– current working directory
And the following source and destination lists…
- char *srcObjs[] = {"trimesh", "../ucd_dir/ucdmesh", "/quad_dir/quadmesh", "trimesh"};
- char *dstObjs[] = {"/tmp/foo/bar/gorfo", "../foogar", 0, "foo"};
Then, DBCpListedObjects(4, dbfile, srcObjs, dbfile2, dstObjs) does the following…
1. Copies trimesh in cwg of dbfile to /tmp/foo/bar/gorfo in dbfile2
2. Copies ../ucd_dir/ucdmesh of dbfile to /foogar in dbfile2
3. Copies /quad_dir/quadmesh to cwg (e.g. /tmp) /tmp/quadmesh in dbfile2
4. Copies trimesh in cwg of dbfile to cwg/foo (/tmp/foo/trimesh in dbfile2`

`DBCp()`

Summary: Generalized copy function emulating unix cp

C Signature:

int DBCp(char const *opts, DBfile *srcFile, DBfile *dstFile, ...)

Fortran Signature:
```
None
```

Arguments:

Arg name	Description
`opts`	A space-separated options string.
`srcFile`	The file holding the source objects to be copied.
`dstFile`	The file holding the destination object paths into which source objects will be copied.
`...`	A `varargs` list of remaining arguments terminated in `DB_EOA` (end of arguments).

Return value:

0 on success. -1 on failure.
Description:

This is the Silo equivalent of a unix cp command obeying all unix semantics and applicable flags and works on either above any driver. This means the method can be used for PDB files, HDF5 files or even a mixture of drivers. In particular, it can be used to copy a whole file from one low-level driver to another.
- Copy a single source object to a single destination object
  - DBCp("", srcFile, dstFile, srcPATH, dstPATH, DB_EOA);`
- Copy multiple source objects to single destination (dir) object
  - DBCp("", srcFile, dstFile, srcPATH1, srcPATH2, ..., dstDIR, DB_EOA);`
- Copy multiple source objects to multiple destination objects
  - DBCp("-2", DBfile *srcFile, DBfile *dstFile, char const *srcPATH1, char const *dstPATH1, char const *srcPATH2, char const *dstPATH2, char const *srcPATH3, char const *dstPATH3, ..., DB_EOA);
srcFile and dstFile may be the same Silo file. srcFile cannot be null. dstFile may be null in which case it is assumed same as srcFile. The argument list must be terminated by the DB_EOA sentinel. Just as for unix cp, the options and their meanings are…
- -R/-r: recurse on any directory objects.
- -L/-P: dereference links / never dereference links.
- -d: preserve links.
- -s/-l: don’t actually copy, just sym/hard link (only possible when srcFile==dstFile).
There are some additional options specific to Silo’s DBCp…
- -2: treat varargs list of args as src/dst path pairs and where any NULL dst is inferred to have same path as associated src except that relative paths are interpreted relative to dst file’s cwg.
- -1: like -2 except caller passes only src paths. All dst paths are inferred to be same as associated src path. The dst file’s cwg will then determine how any relative src paths are interpreted.
- -3 only 3 args follow the dstFile arg…
  - int N: number of objects in the following lists.
  - DBCAS_t srcPathNames: list of N source path names.
  - DBCAS_t dstPathNames: list of N destination path names.
  - In this case, a terminating DB_EOA is not necessary.
- -4: Like -3, except 3rd arg is treated as a single dst dir name.
  - int N: number of paths in srcPathNames.
  - DBCAS_t srcPathNames: list of N source path names.
  - char const *dstDIR: pre-existing destination dir path.
  - In this case, a terminating DB_EOA is not necessary.
- -5: Internal use only…like -4 except used only internally when DBCp recursively calls itself.
Other rules:
- If any src is a dir, then the operation is an error without -R/-r option.
- If cooresponding dst exists and is a dir, src is copied into (e.g. becomes a child of) dst.
- If cooresponding dst exists and is not a dir (e.g. is just a normal Silo object), then it is an error if src is not also the same kind of Silo object. The copy overwrites (destructively) dst. However, if the file space dst object occupies is smaller than that needed to copy src, behavior is indeterminate but may will result in the dst file (not just the dst object) being corrupted.
If none of the preceding numeric arguments are specified, then the varags list of args is treated as (default) where the last is a pre-existing destination directory and all the others are the paths of source objects to be copied into that directory.

Relative path names are interpreted relative to the current working directory of the associated (src or dst) file when DBCp is invoked.

In all the different ways this function can be invoked, there are really just two fundamentally different interpretations of the list(s) of names. Either each source path is paired also with a destination path or all source paths go into a single destination path which, just as for linux cp, must then also be a directory already present in the destination.

`DBGrabDriver()`

Summary: Obtain the low-level driver file handle
C Signature:
```
void *DBGrabDriver(DBfile *file)
```
Fortran Signature:
```
None
```
Arguments:

Arg name

Description

file

The Silo database file handle.
Returned value:

A void pointer to the low-level driver’s file handle on success. NULL(0) on failure.
Description:

This method is used to obtain the low-level driver’s file handle. For example, one can use it to obtain the HDF5 hid_t returned from the H5Fopen/H5Fcreate call. The caller is responsible for casting the returned pointer to a pointer to the correct type. Use DBGetDriverType() to obtain information on the type of driver currently in use.

When the low-level driver’s file handle is grabbed, all Silo-level operations on file are prevented until file is UNgrabbed. For example, after a call to DBGrabDriver, calls to functions like DBPutQuadmesh or DBGetCurve will fail until the driver is UNgrabbed using DBUngrabDriver().

Notes:

As far as the integrity of a Silo file goes, grabbing is inherently dangerous. If the client is not careful, one can easily wind up corrupting the file for the Silo library (though all may be ‘normal’ for the underlying driver library). Therefore, to minimize the likelihood of corrupting the Silo file while it is grabbed, it is recommended that all operations with the low-level driver grabbed be confined to a separate sub-directory in the silo file. That is, one should not mix writing of Silo objects and low-level driver objects in the same directory. To achieve this, before grabbing, create the desired directory and descend into it using Silo’s DBMkDir() and DBSetDir() functions. Then, grab the driver and do all the work with the low-level driver that is necessary. Finally, ungrab the driver and immediately ascend out of the directory using Silo’s DBSetDir(“..”).

For reasons described above, if problems occur on files that have been grabbed, users will likely be asked to re-produce the problem on a similar file that has not been grabbed to rule out possible corruption from grabbing.

`DBUngrabDriver()`

Summary: Ungrab the low-level file driver

C Signature:

int DBUngrabDriver(DBfile *file, const void *drvr_hndl)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

file

The Silo database file handle.

drvr_hndl

The low-level driver handle.
Returned value:

The driver type on success, DB_UNKNOWN on failure.
Description:

This function returns the Silo file to an ungrabbed state, permitting Silo calls to again proceed as normal.

`DBGetDriverType()`

Summary: Get the type of driver for the specified file

C Signature:

int DBGetDriverType(const DBfile *file)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

file

A Silo database file handle.
Returned value:

DB_UNKNOWN for failure. Otherwise, the specified driver type is returned
Description:

This function returns the type of driver used for the specified file. If you want to ask this question without actually opening the file, use DBGetDriverTypeFromPath.

`DBGetDriverTypeFromPath()`

Summary: Guess the driver type used by a file with the given pathname

C Signature:

int DBGetDriverTypeFromPath(char const *path)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

path

Path to a file on the file system
Returned value:

DB_UNKNOWN on failure to determine type. Otherwise, the driver type such as DB_PDB or DB_HDF5.
Description:

This function examines the first few bytes of the file for tell-tale signs of whether it is a PDB file or an HDF5 file.

If it is a PDB file, it cannot distinguish between a file generated by DB_PDB driver and DB_PDBP (PDB Proper) driver. It will always return DB_PDB for a PDB file.

If the file is an HDF5, the function is currently not implemented to distiniguish between various HDF5 VFDs the file may have been generated with. It will always return DB_HDF5 for an HDF5 file.

Note, this function will determine only whether the underlying file is a PDB or HDF5 file. It will not however, indicate whether the file is a PDB or HDF5 file that was indeed generated by Silo and is readable by Silo. See DBInqFile for a function that will indicate whether the file is indeed a Silo file. Note, however, that DBInqFile is a more expensive operation.

`DBInqFile()`

Summary: Inquire if filename is a Silo file.
C Signature:
```
int DBInqFile (char const *filename)
```

Fortran Signature:

integer function dbinqfile(filename, lfilename, is_file)

Arguments:

Arg name

Description

filename

Name of file.
Returned value:

DBInqFile returns 0 if filename is not a Silo file, a positive number if filename is a Silo file, and a negative number if an error occurred.
Description:

The DBInqFile function is mainly used for its return value, as seen above.

Prior to version 4.7.1 of the Silo library, this function could return false positives when the filename referred to a PDB file that was not created by Silo. The reason for this is that all this function really did was check whether or not DBOpen would succeed on the file.

Starting in version 4.7.1 of the Silo library, this function will attempt to count the number of Silo objects (not including directories) in the first non-empty directory it finds. If it cannot find any Silo objects in the file, it will return zero (0) indicating the file is not a Silo file.

Because very early versions of the Silo library did not store anything to a Silo file to distinguish it from a PDB file, it is conceivable that this function will return false negatives for very old, empty Silo files. But, that case should be rare.

Similar problems do not exist for HDF5 files because Silo’s HDF5 driver has always stored information in the HDF5 file which helps to distinguish it as a Silo file.

`DBInqFileHasObjects()`

Summary: Determine if an open file has any Silo objects

C Signature:

int DBInqFileHasObjects(DBfile *dbfile)

Fortran Signature:
```
None
```
Arguments:

Arg name

Description

dbfile

The Silo database file handle
Description:

Examine an open file for existence of any Silo objects.

`_silolibinfo`

Summary: A character array written by Silo to root directory indicating the Silo library version number used to generate the file

C Signature:

    int n;
    char vers[1024];
    sprintf(vers, "silo-4.6");
    n = strlen(vers);
    DBWrite(dbfile, "_silolibinfo", vers, &n, 1, DB_CHAR);

Description:

This is a simple array variable written at the root directory in a Silo file that contains the Silo library version string. It cannot be disabled.

`_hdf5libinfo`

Summary: character array written by Silo to root directory indicating the HDF5 library version number used to generate the file

C Signature:

    int n;
    char vers[1024];
    sprintf(vers, "hdf5-1.6.6");
    n = strlen(vers);
    DBWrite(dbfile, "_hdf5libinfo", vers, &n, 1, DB_CHAR);

Description:

This is a simple array variable written at the root directory in a Silo file that contains the HDF5 library version string. It cannot be disabled. Of course, it exists, only in files created with the HDF5 driver.

`_was_grabbed`

Summary: single integer written by Silo to root directory whenever a Silo file has been grabbed.

C Signature:

    int n=1;
    DBWrite(dbfile, "_was_grabbed", &n, &n, 1, DB_INT);

Description:

This is a simple array variable written at the root directory in a Silo whenever a Silo file has been grabbed by the DBGrabDriver() function. It cannot be disabled.

Files and File Structure

DBRegisterFileOptionsSet()

DBUnregisterFileOptionsSet()

DBUnregisterAllFileOptionsSets()

DBSetUnknownDriverPriorities()

DBGetUnknownDriverPriorities()

DBCreate()

DBOpen()

DBFlush()

DBClose()

DBGetToc()

File-level properties

DBFileName()

DBFileVersion()

DBFileVersionDigits()

DBFileVersionGE()

DBVersionGEFileVersion()

DBSortObjectsByOffset()

DBMkDir()

DBMkDirP()

DBSetDir()

DBGetDir()

DBCpDir()

DBCpListedObjects()

DBCp()

DBGrabDriver()

DBUngrabDriver()

DBGetDriverType()

DBGetDriverTypeFromPath()

DBInqFile()

DBInqFileHasObjects()

_silolibinfo

_hdf5libinfo

_was_grabbed

`DBRegisterFileOptionsSet()`

`DBUnregisterFileOptionsSet()`

`DBUnregisterAllFileOptionsSets()`

`DBSetUnknownDriverPriorities()`

`DBGetUnknownDriverPriorities()`

`DBCreate()`

`DBOpen()`

`DBFlush()`

`DBClose()`

`DBGetToc()`

`DBFileName()`

`DBFileVersion()`

`DBFileVersionDigits()`

`DBFileVersionGE()`

`DBVersionGEFileVersion()`

`DBSortObjectsByOffset()`

`DBMkDir()`

`DBMkDirP()`

`DBSetDir()`

`DBGetDir()`

`DBCpDir()`

`DBCpListedObjects()`

`DBCp()`

`DBGrabDriver()`

`DBUngrabDriver()`

`DBGetDriverType()`

`DBGetDriverTypeFromPath()`

`DBInqFile()`

`DBInqFileHasObjects()`

`_silolibinfo`

`_hdf5libinfo`

`_was_grabbed`