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

# tcflow(3)

suspect transmission or reception of data

## NAME

tcflow - suspect transmission or reception of data

## LIBRARY

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

## SYNOPSIS

```
#include <termios.h>
```

**int tcflow(int** *fd***, int** *action***);**

## DESCRIPTION

**tcflow**() suspends transmission or reception of data on the object referred to by *fd*, depending on the value of *action*:

- **TCOOFF**

  suspends output.

- **TCOON**

  restarts suspended output.

- **TCIOFF**

  transmits a STOP character, which stops the terminal device from transmitting data to the system.

- **TCION**

  transmits a START character, which starts the terminal device transmitting data to the system.

The default on open of a terminal file is that neither its input nor its output is suspended.

## RETURN VALUE

- **0**

  on success.

- **-1**

  on failure and set *errno* to indicate the error.

## ATTRIBUTES

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

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

## STANDARDS

POSIX.1-2008.

## HISTORY

POSIX.1-2001.

## SEE ALSO

[**tcsendbreak**(3)](/tcsendbreak/3.md), [**tcdrain**(3)](/tcdrain/3.md), [**tcflush**(3)](/tcflush/3.md), [**termios**(7)](/termios/7.md)