4.3BSD-UWisc/man/cat3/siginterrupt.3

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SIGINTERRUPT(3)     UNIX Programmer's Manual      SIGINTERRUPT(3)



NAME
     siginterrupt - allow signals to interrupt system calls

SYNOPSIS
     siginterrupt(sig, flag);
     int sig, flag;

DESCRIPTION
     _S_i_g_i_n_t_e_r_r_u_p_t is used to change the system call restart
     behavior when a system call is interrupted by the specified
     signal.  If the flag is false (0), then system calls will be
     restarted if they are interrupted by the specified signal
     and no data has been transferred yet.  System call restart
     is the default behavior on 4.2 BSD.

     If the flag is true (1), then restarting of system calls is
     disabled.  If a system call is interrupted by the specified
     signal and no data has been transferred, the system call
     will return -1 with errno set to EINTR.  Interrupted system
     calls that have started transferring data will return the
     amount of data actually transferred.  System call interrupt
     is the signal behavior found on 4.1 BSD and AT&T System V
     UNIX systems.

     Note that the new 4.2 BSD signal handling semantics are not
     altered in any other way.  Most notably, signal handlers
     always remain installed until explicitly changed by a subse-
     quent _s_i_g_v_e_c(2) call, and the signal mask operates as docu-
     mented in _s_i_g_v_e_c(2).  Programs may switch between restart-
     able and interruptible system call operation as often as
     desired in the execution of a program.

     Issuing a _s_i_g_i_n_t_e_r_r_u_p_t(3) call during the execution of a
     signal handler will cause the new action to take place on
     the next signal to be caught.

NOTES
     This library routine uses an extension of the _s_i_g_v_e_c(2) sys-
     tem call that is not available in 4.2BSD, hence it should
     not be used if backward compatibility is needed.

RETURN VALUE
     A 0 value indicates that the call succeeded.  A -1 value
     indicates that an invalid signal number has been supplied.

SEE ALSO
     sigvec(2), sigblock(2), sigpause(2), sigsetmask(2).








Printed 12/27/86          May 15, 1985                          1