unix-signals

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1 Introduction

This library provides a means of sending and receiving Unix signals to Racket programs.

Be warned that attempting to receive certain signals used by the Racket runtime is dangerous, as the code here will conflict with the code in Racket itself.

2 What to require

All the functionality below can be accessed with a single require:

This library represents signal names as symbols all in upper-case; for example, 'SIGUSR1 and 'SIGKILL.

2.1 Waiting for a signal

To receive Unix signals using this library, call capture-signal! once for each signal of interest, and then use next-signal-evt or read-signal. Use ignore-signal! and release-signal! to ignore a signal (SIG_IGN) or to install the default signal-handler (SIG_DFL), respectively.

(require unix-signals)

(capture-signal! 'SIGUSR1)

(capture-signal! 'SIGUSR2)

(printf "Try 'kill -USR1 ~a' and 'kill -USR2 ~a'\n" (getpid) (getpid))

(let loop ()

(define signum (read-signal))

(printf "Received signal ~v (name ~v)\n" signum (lookup-signal-name signum))

(loop))

Calls to capture-signal! and friends have global effect within the Racket process. Likewise, use of next-signal-evt and read-signal have global side-effects on the state of the Racket process.

2.2 Sending a signal

This library provides getpid from racket/os for convenience.

2.3 Mapping between signal names and signal numbers