---
name: "gelf_update_auxv"
section: "3"
platform: "linux"
package: "libelf"
version: "0.197-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gelf_update_auxv"
---

# gelf\_update\_auxv(3)

Update information in the auxiliary vector at the given index

## NAME

gelf\_update\_auxv - Update information in the auxiliary vector at the given index

## SYNOPSIS

```
#include <gelf.h>
int gelf_update_auxv (Elf_Data *data, int ndx, GElf_auxv_t *src);
```

## DESCRIPTION

Copy a class-independent auxiliary vector entry from *src* into the **NT\_AUXV** note associated with *data* at index *ndx*. See [**getauxval**(3)](/getauxval/3.md) for more information regarding the auxiliary vector.

## PARAMETERS

- *data*

  Pointer to an **Elf\_Data** associated with an **NT\_AUXV** ELF note. *data-\>d\_type* should be **ELF\_T\_AUXV**. **NT\_AUXV** notes are normally found in core files.  The auxiliary vector can also be read directly from /proc/PID/auxv of a live process, in which case this function does not write back to *data* itself.

- *ndx*

  Zero-based index of the auxiliary vector entry to be updated within *data*.

- *src*

  Pointer to a caller-provided auxiliary vector entry.  For **ELFCLASS32** binaries, **a\_type** and **a\_val** must fit within unsigned 32-bit values. *src* must not be NULL.

## RETURN VALUE

On success, this function returns a non-zero value, updates the auxiliary vector entry at index *ndx* in *data*, and marks the section or segment associated with *data* with **ELF\_F\_DIRTY**. On failure, zero is returned and elf\_errno is set.  If *data* is NULL, then zero is returned without setting elf\_errno.

## SEE ALSO

[**gelf\_getauxv**(3)](/gelf_getauxv/3.md), [**getauxval**(3)](/getauxval/3.md), [**libelf**(3)](/libelf/3.md), [**elf**(5)](/elf/5.md)

## ATTRIBUTES

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **gelf\_update\_auxv**() | Thread safety | MT-Safe |

## REPORTING BUGS

Report bugs to \<elfutils-devel@sourceware.org\> or https://sourceware.org/bugzilla/.

## HISTORY