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

# gd\_carrays(3)

retrieve a list of CARRAY values from a Dirfile

## NAME

gd\_carrays, gd\_mcarrays — retrieve a list of CARRAY values from a Dirfile

## SYNOPSIS

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

**const gd\_carray\_t \*gd\_carrays(DIRFILE \****dirfile***, gd\_type\_t** *return\_type***);**

**const gd\_carray\_t \*gd\_mcarrays(DIRFILE \****dirfile***, const char** **\****parent***, gd\_type\_t** *return\_type***);**

## DESCRIPTION

The **gd\_carrays**() function queries a [dirfile(5)](/dirfile/5.md) database specified by *dirfile* and generates a read-only list of values of the all top-level **CARRAY** fields defined in the database, after type conversion to the data type specified by *return\_type*. For a list of valid symbols to use for *return\_type*, see the [**gd\_get\_carray**(3)](/gd_get_carray/3.md) manual page.

The **gd\_mcarrays**() function behaves similarly, but creates a list of values of **CARRAY** subfields under the parent field *parent*.

The  *dirfile* argument must point to a valid DIRFILE object previously created by a call to [**gd\_open**(3)](/gd_open/3.md).

A corresponding list of names for these fields may be obtained by calling [**gd\_field\_list\_by\_type**(3)](/gd_field_list_by_type/3.md) or [**gd\_mfield\_list\_by\_type**(3)](/gd_mfield_list_by_type/3.md).

## RETURN VALUE

Upon successful completion, **gd\_carrays**() and [**gd\_mcarrays**(3)](/gd_mcarrays/3.md) return a pointer to an array of **gd\_carray\_t** objects containing the values of all the CARRAYs defined in the dirfile database.  The **gd\_carray\_t** structure is defined as:

```
typedef struct {
  size_t       n;              /* array_len */
  void        *d;              /* CARRAY data */
} gd_carray_t;
```

where *n* specifies the length of the **CARRAY** data, and *d* is an array of the data values themselves. If *return\_type* was **GD\_NULL**, *d* will be NULL.  Otherwise, the caller should cast the **void** pointer to a type appropriate for the *return\_type* specified.  The list is terminated by an end-of-list marker consisting of a **gd\_carray\_t** item with *n* set to zero.

If no CARRAYs are defined in the database, a list containing only the end-of-list marker is returned.

The array returned will be de-allocated by a call to [**gd\_close**(3)](/gd_close/3.md) and should not be de-allocated by the caller.  The list returned should not be assumed to be in any particular order, except that it is guaranteed to be in the same order as the list of **CARRAY** fields returned by [**gd\_field\_list\_by\_type**(3)](/gd_field_list_by_type/3.md) or [**gd\_mfield\_list\_by\_type**(3)](/gd_mfield_list_by_type/3.md). The number of values in the array can be obtained from a call to [**gd\_nfields\_by\_type**(3)](/gd_nfields_by_type/3.md) or [**gd\_nmfields\_by\_type**(3)](/gd_nmfields_by_type/3.md).

The caller may not modify any values in the array, nor the array itself.  Doing so may cause database corruption.  The pointer returned is guaranteed to be valid only until the function is called again, or until the dirfile's metadata is modified (by adding, modifying or deleting an entry), or until the array is de-allocated by a call to [**gd\_close**(3)](/gd_close/3.md) or [**gd\_discard**(3)](/gd_discard/3.md).

On error, **gd\_carrays**() returns NULL and stores a negative-valued error code in the **DIRFILE** object which may be retrieved by a subsequent call to [**gd\_error**(3)](/gd_error/3.md). 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\_BAD\_TYPE** The *return\_type* specified was invalid.\
  .TP 8 **GD\_E\_INTERNAL\_ERROR** An internal error occurred in the library while trying to perform the task. This indicates a bug in the library.  Please report the incident to the GetData developers.

A descriptive error string for the error may be obtained by calling [**gd\_error\_string**(3)](/gd_error_string/3.md).

## HISTORY

The **gd\_carrays**() and **gd\_mcarrays**() functions appeared in GetData-0.7.0.

## SEE ALSO

[dirfile(5)](/dirfile/5.md), [**gd\_error**(3)](/gd_error/3.md), [**gd\_error\_string**(3)](/gd_error_string/3.md), [**gd\_field\_list\_by\_type**(3)](/gd_field_list_by_type/3.md), [**gd\_get\_carray**(3)](/gd_get_carray/3.md), [**gd\_mfield\_list\_by\_type**(3)](/gd_mfield_list_by_type/3.md), [**gd\_nfields\_by\_type**(3)](/gd_nfields_by_type/3.md) [**gd\_nmfields\_by\_type**(3)](/gd_nmfields_by_type/3.md) [**gd\_open**(3)](/gd_open/3.md)