---
name: "tcgetsid"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/tcgetsid"
---

# tcgetsid(3)

get session ID

## NAME

tcgetsid - get session ID

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#define _XOPEN_SOURCE 500        /* See feature_test_macros(7) */
#include <termios.h>
```

**pid\_t tcgetsid(int** *fd***);**

## DESCRIPTION

The function **tcgetsid**() returns the session ID of the current session that has the terminal associated to *fd* as controlling terminal. This terminal must be the controlling terminal of the calling process.

## RETURN VALUE

When *fd* refers to the controlling terminal of our session, the function **tcgetsid**() will return the session ID of this session. Otherwise, -1 is returned, and *errno* is set to indicate the error.

## ERRORS

- **EBADF**

  *fd* is not a valid file descriptor.

- **ENOTTY**

  The calling process does not have a controlling terminal, or it has one but it is not described by *fd*.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **tcgetsid**() | Thread safety | MT-Safe |

## STANDARDS

POSIX.1-2008.

## HISTORY

glibc 2.1. POSIX.1-2001.

This function is implemented via the **TIOCGSID** [**ioctl**(2)](/ioctl/2.md), present since Linux 2.1.71.

## SEE ALSO

[**getsid**(2)](/getsid/2.md)