---
name: "gd_open_limit"
section: "3"
platform: "linux"
package: "libgetdata-doc"
version: "0.11.0-15"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/gd_open_limit"
---

# gd\_open\_limit(3)

set a Dirfile's allowed number of open files

## NAME

gd\_open\_limit — set a Dirfile's allowed number of open files

## SYNOPSIS

**#include \<getdata.h\>**

**long gd\_open\_limit(DIRFILE \****dirfile***, long** *limit***);**

## DESCRIPTION

The **gd\_open\_limit**() function can be used to limit the number of **RAW** file descriptors which GetData simultaneously holds open in the open [dirfile(5)](/dirfile/5.md) database specified by *dirfile*. This function can also be used to report the current number of open files, or the current limit.  When limiting is active, to stay below the limit, GetData will automatically close the least recently accessed **RAW** fields (as if [**gd\_raw\_close**(3)](/gd_raw_close/3.md) were called), when needed.

The default value for the limit is zero, indicating that limiting is disabled. In this case, GetData will never automatically close open **RAW** fields.  To enable limiting call this function with a positive value for *limit*. If limited, the minimum limit is two; if this function is passed a *limit* of one, it will behave as if the value 2 were passed instead.

When setting a limit, this function will immediately close enough **RAW** fields to remain below the specified limit.

The argument *limit* may alternately be one of the following special values:\
  .TP 8 **GD\_OLIMIT\_NONE (=0)** Disable limiting, if it was previously active.\
  .TP 8 **GD\_OLIMIT\_CURRENT** Do nothing other than report the current limit.  This is equivalent to calling this function with *limit* equal to the current limit.\
  .TP 8 **GD\_OLIMIT\_COUNT** Instead of returning the current limit, return the current number filed descriptors for this dirfile.  The current limit is not changed.

## RETURN VALUE

If *limit* is **GD\_OLIMIT\_COUNT**, then the current number of file descriptors in use by this dirfile is returned, or zero if limiting is disabled (i.e. the limit is zero).

For other values of *limit*, if successful, this function returns the open field limit, after possibly modifying it.  This limit is never negative.  It will be zero if limiting is disabled.

If *limit* is one of the special values **GD\_OLIMIT\_COUNT**, **GD\_OLIMIT\_CURRENT**, or **GD\_OLIMIT\_NONE (=0),** then this function always succeeds.  Otherwise, on error, **gd\_open\_limit**() returns a negative-valued error code.  Possible error codes are:\
  .TP 8 **GD\_E\_ALLOC** The library was unable to allocate memory.\
  .TP 8 **GD\_E\_BAD\_DIRFILE** The supplied dirfile was invalid.\
  .TP 8 **GD\_E\_IO** An I/O error occurred while trying to write modified data to disk as a result in a reduction of the open field limit.

The error code is also stored in the **DIRFILE** object and may be retrieved after this function returns by calling [**gd\_error**(3)](/gd_error/3.md). A descriptive error string for the error may be obtained by calling [**gd\_error\_string**(3)](/gd_error_string/3.md).

## NOTES

The file descriptors tracked by this functionality are only those associated with **RAW** fields which are held open across function calls.  During the course of any library call, GetData may temporarily exceed a file descriptor limit set with this function without triggering an automatic close.  Some headroom is always a good idea.

Furthermore, this limit is specific to the specified *dirfile*. It is not a global limit for the whole GetData library.  If a process has multiple **DIRFILE**s open, each of them has its own limit (or is unlimited), even though they all draw from the same limited pool of file descriptors.

In some cases, usually when writing to a compressed **RAW** field, two file descriptors may be held open for a single field.

## HISTORY

The **gd\_open\_limit**() function appeared in GetData-0.11.0.

## SEE ALSO

[**gd\_error**(3)](/gd_error/3.md), [**gd\_error\_string**(3)](/gd_error_string/3.md), [**gd\_open**(3)](/gd_open/3.md), [**gd\_raw\_close**(3)](/gd_raw_close/3.md), **getrlimit**(3), [**ulimit**(3)](/ulimit/3.md), [dirfile(5)](/dirfile/5.md)