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Manual Reference Pages  - system_signal (3m_system)

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NAME

system_signal(3f) - [M_system:SIGNALS] install a signal handler (LICENSE:PD)

CONTENTS

Synopsis
Description
Examples
Author
License

SYNOPSIS

subroutine system_signal(sig,handler)

     integer,intent(in) :: sig
     interface
       subroutine handler(signum)
       integer :: signum
       end subroutine handler
     end interface
     optional :: handler

DESCRIPTION

Calling system_signal(NUMBER, HANDLER) causes user-defined subroutine HANDLER to be executed when the signal NUMBER is caught. The same subroutine HANDLER maybe installed to handle different signals. HANDLER takes only one integer argument which is assigned the signal number that is caught. See sample program below for illustration.

Calling system_signal(NUMBER) installs a do-nothing handler. This is not equivalent to ignoring the signal NUMBER though, because the signal can still interrupt any sleep or idle-wait.

Note that the signals SIGKILL and SIGSTOP cannot be handled this way.

[Compare signal(2) and the GNU extension signal in gfortran.]

EXAMPLES

Sample program:

    program demo_system_signal
    use M_system, only : system_signal
    implicit none
    logical :: loop=.true.
    integer, parameter :: SIGINT=2,SIGQUIT=3
    call system_signal(SIGINT,exitloop)
    call system_signal(SIGQUIT,quit)
    write(*,*)’Starting infinite loop. Press Ctrl+C to exit.’
    do while(loop)
    enddo
    write(*,*)’Reporting from outside the infinite loop.’
    write(*,*)’Starting another loop. Do Ctrl+\ anytime to quit.’
    loop=.true.
    call system_signal(2)
    write(*,*)&
     & ’Just installed do-nothing handler for SIGINT. Try Ctrl+C to test.’
    do while(loop)
    enddo
    write(*,*)’You should never see this line when running this demo.’

    contains

    subroutine exitloop(signum)
      integer :: signum
      write(*,*)’Caught SIGINT. Exiting infinite loop.’
      loop=.false.
    end subroutine exitloop

    subroutine quit(signum)
      integer :: signum
      STOP ’Caught SIGQUIT. Stopping demo.’
    end subroutine quit
    end program demo_system_signal

AUTHOR

Somajit Dey

LICENSE

Public Domain

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Nemo Release 3.1

system_signal (3m_system)

March 07, 2025

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