---
name: "backfire"
section: "4"
platform: "linux"
package: "rt-tests"
version: "1.0-1+b1"
release: "Debian 9 (Stretch)"
platforms: ["linux"]
url: "https://new.carta.tech/backfire"
---

# backfire(4)

send a signal from driver to user

## NAME

backfire - send a signal from driver to user

## DESCRIPTION

The **backfire** driver reads a numerical string that is sent to the
 **/dev/backfire** device and sends the corresponding signal to the calling
 user program. Reading from **/dev/backfire** returns the time of the day
 when the most recent sent request was serviced or 0, if a sent request was
 not yet received. The time of the day is displayed in seconds since
 1970-01-01 00:00:00 UTC followed by the fraction of the second in
 microseconds separated by a comma.

## PURPOSE

The **backfire** driver is normally used in combination with the program
 **sendme** to benchmark the performance of the kernel's signal sending
 capabilities.

## EXAMPLES

head -1 /dev/backfire
 0,0
 trap "echo Got signal 7" 7
 echo 7 \>/dev/backfire
 Got signal 7
 head -1 /dev/backfire
 1234567890,123456

## AUTHORS

Carsten Emde \<C.Emde@osadl.org\>

## SEE ALSO

[sendme(8)](/sendme/8.md)