---
name: "ctermid"
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/ctermid"
---

# ctermid(3)

get controlling terminal name

## NAME

ctermid - get controlling terminal name

## LIBRARY

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

## SYNOPSIS

```
#include <stdio.h>
```

**char \*ctermid(char \****s***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**ctermid**():

```
    _POSIX_C_SOURCE
```

## DESCRIPTION

**ctermid**() returns a string which is the pathname for the current controlling terminal for this process. If *s* is NULL, a static buffer is used, otherwise *s* points to a buffer used to hold the terminal pathname. The symbolic constant **L\_ctermid** is the maximum number of characters in the returned pathname.

## RETURN VALUE

The pointer to the pathname.

## ATTRIBUTES

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

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

## STANDARDS

POSIX.1-2008.

## HISTORY

POSIX.1-2001, Svr4.

## BUGS

The returned pathname may not uniquely identify the controlling terminal; it may, for example, be */dev/tty*.

It is not assured that the program can open the terminal.

## SEE ALSO

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