---
name: "pcap_init"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/pcap_init"
---

# pcap\_init(3)

initialize the library

## NAME

pcap\_init - initialize the library

## SYNOPSIS

```
#include <pcap/pcap.h>
```

```
char errbuf[PCAP_ERRBUF_SIZE];
```

**int pcap\_init(unsigned int opts, char \*errbuf);**

## DESCRIPTION

**pcap\_init**() is used to initialize the Packet Capture library. *opts* specifies options for the library; *errbuf* is a buffer large enough to hold at least **PCAP\_ERRBUF\_SIZE** chars.

Currently, the options that can be specified in *opts* are:

- **PCAP\_CHAR\_ENC\_LOCAL**

  Treat all strings supplied as arguments, and return all strings to the caller, as being in the local character encoding.

- **PCAP\_CHAR\_ENC\_UTF\_8**

  Treat all strings supplied as arguments, and return all strings to the caller, as being in UTF-8.

On UNIX-like systems, the local character encoding is assumed to be UTF-8, so no character encoding transformations are done.

On Windows, the local character encoding is the local ANSI code page.

If **pcap\_init**() is not called, strings are treated as being in the local ANSI code page on Windows, [**pcap\_lookupdev**(3)](/pcap_lookupdev/3.md) will succeed if there is a device on which to capture, and [**pcap\_create**(3)](/pcap_create/3.md) makes an attempt to check whether the string passed as an argument is a UTF-16LE string - note that this attempt is unsafe, as it may run past the end of the string - to handle **pcap\_lookupdev**() returning a UTF-16LE string. Programs that don't call **pcap\_init**() should, on Windows, call **pcap\_wsockinit**() to initialize Winsock; this is not necessary if **pcap\_init**() is called, as **pcap\_init**() will initialize Winsock itself on Windows.

## RETURN VALUE

**pcap\_init**() returns **0** on success and **PCAP\_ERROR** on failure. If **PCAP\_ERROR** is returned, *errbuf* is filled in with an appropriate error message.

## BACKWARD COMPATIBILITY

This function became available in libpcap release 1.9.0.  In previous releases, on Windows, all strings supplied as arguments, and all strings returned to the caller, are in the local character encoding.

## SEE ALSO

[**pcap**(3)](/pcap/3.md)