gen/siginterrupt.3

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  32 .\"     @(#)siginterrupt.3      8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/lib/libc/gen/siginterrupt.3,v 1.14 2002/12/19 09:40:21 ru Exp $
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  35 .Dd June 4, 1993
  36 .Dt SIGINTERRUPT 3
  37 .Os
  38 .Sh NAME
  39 .Nm siginterrupt
  40 .Nd allow signals to interrupt system calls
  41 .Sh LIBRARY
  42 .Lb libc
  43 .Sh SYNOPSIS
  44 .In signal.h
  45 .Ft int
  46 .Fn siginterrupt "int sig" "int flag"
  47 .Sh DESCRIPTION
  48 The
  49 .Fn siginterrupt
  50 function
  51 is used to change the system call restart
  52 behavior when a system call is interrupted by the specified signal.
  53 If the flag is false (0), then system calls will be restarted if
  54 they are interrupted by the specified signal
  55 and no data has been transferred yet.
  56 System call restart has been the default behavior since
  57 .Bx 4.2 ,
  58 and is the default behaviour for
  59 .Xr signal 3
  60 on
  61 .Fx .
  62 .Pp
  63 If the flag is true (1),
  64 then restarting of system calls is disabled.
  65 If a system call is interrupted by the specified signal
  66 and no data has been transferred,
  67 the system call will return \-1 with the global variable
  68 .Va errno
  69 set to
  70 .Er EINTR .
  71 Interrupted system calls that have started transferring
  72 data will return the amount of data actually transferred.
  73 System call interrupt is the signal behavior found on
  74 .Bx 4.1
  75 and
  76 .At V
  77 systems.
  78 .Pp
  79 Note that the new
  80 .Bx 4.2
  81 signal handling semantics are not
  82 altered in any other way.
  83 Most notably, signal handlers always remain installed until
  84 explicitly changed by a subsequent
  85 .Xr sigaction 2
  86 call, and the signal mask operates as documented in
  87 .Xr sigaction 2 .
  88 Programs may switch between restartable and interruptible
  89 system call operation as often as desired in the execution of a program.
  90 .Pp
  91 Issuing a
  92 .Fn siginterrupt 3
  93 call during the execution of a signal handler will cause
  94 the new action to take place on the next signal to be caught.
  95 .Sh NOTES
  96 This library routine uses an extension of the
  97 .Xr sigaction 2
  98 system call that is not available in
  99 .Bx 4.2 ;
 100 hence, it should not be used if backward compatibility is needed.
 101 .Sh RETURN VALUES
 102 .Rv -std siginterrupt
 103 .Sh ERRORS
 104 The
 105 .Fn siginterrupt
 106 call fails if:
 107 .Bl -tag -width Er
 108 .It Bq Er EINVAL
 109 The
 110 .Fa sig
 111 argument
 112 is not a valid signal number.
 113 .El
 114 .Sh SEE ALSO
 115 .Xr sigaction 2 ,
 116 .Xr sigblock 2 ,
 117 .Xr sigpause 2 ,
 118 .Xr sigsetmask 2 ,
 119 .Xr signal 3
 120 .Sh HISTORY
 121 The
 122 .Fn siginterrupt
 123 function appeared in
 124 .Bx 4.3 .