---
name: "gnutls_session_set_verify_output_function"
section: "3"
platform: "linux"
package: "gnutls"
version: "3.8.13-3"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/gnutls_session_set_verify_output_function"
---

# gnutls\_session\_set\_verify\_output\_function(3)

API function

## NAME

gnutls\_session\_set\_verify\_output\_function - API function

## SYNOPSIS

**#include \<gnutls/x509.h\>**

**void gnutls\_session\_set\_verify\_output\_function(gnutls\_session\_t** *session***, gnutls\_verify\_output\_function \*** *func***);**

## ARGUMENTS

- gnutls\_session\_t session

  is a **gnutls\_x509\_trust\_list\_t** type.

- gnutls\_verify\_output\_function \* func

  is the callback function

## DESCRIPTION

This function sets a callback to be called when the peer's certificate chain has to be verified and full path to the trusted root has to be printed.

The callback's function prototype is defined in \`x509.h': int (\*callback)( gnutls\_x509\_crt\_t cert, gnutls\_x509\_crt\_t issuer, gnutls\_x509\_crl\_t crl, unsigned int verification\_output);

If the callback function is provided then gnutls will call it, in the certificate verification procedure. To verify the certificate chain and print its path uptp the trusted root, functions such as **gnutls\_certificate\_verify\_peers()**, **gnutls\_x509\_trust\_list\_verify\_crt()**, and **gnutls\_x509\_trust\_list\_verify\_crt2()** can be used. The callback is set in **\_gnutls\_verify\_crt\_status()** and **\_gnutls\_pkcs11\_verify\_crt\_status()**.

## SINCE

3\.7.0

## REPORTING BUGS

Report bugs to \<bugs@gnutls.org\>.\
 Home page: https://www.gnutls.org

## COPYRIGHT

Copyright © 2001-2023 Free Software Foundation, Inc., and others.\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **gnutls** is maintained as a Texinfo manual. If the /usr/share/doc/gnutls/ directory does not contain the HTML form visit

- https://www.gnutls.org/manual/