gen/FreeBSD/siginterrupt.3

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  28 .\"     @(#)siginterrupt.3      8.1 (Berkeley) 6/4/93
  29 .\" $FreeBSD: src/lib/libc/gen/siginterrupt.3,v 1.15 2007/01/09 00:27:55 imp Exp $
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  31 .Dd June 4, 1993
  32 .Dt SIGINTERRUPT 3
  33 .Os
  34 .Sh NAME
  35 .Nm siginterrupt
  36 .Nd allow signals to interrupt system calls
  37 .Sh LIBRARY
  38 .Lb libc
  39 .Sh SYNOPSIS
  40 .In signal.h
  41 .Ft int
  42 .Fn siginterrupt "int sig" "int flag"
  43 .Sh DESCRIPTION
  44 The
  45 .Fn siginterrupt
  46 function
  47 is used to change the system call restart
  48 behavior when a system call is interrupted by the specified signal.
  49 If the flag is false (0), then system calls will be restarted if
  50 they are interrupted by the specified signal
  51 and no data has been transferred yet.
  52 System call restart has been the default behavior since
  53 .Bx 4.2 ,
  54 and is the default behaviour for
  55 .Xr signal 3
  56 on
  57 .Fx .
  58 .Pp
  59 If the flag is true (1),
  60 then restarting of system calls is disabled.
  61 If a system call is interrupted by the specified signal
  62 and no data has been transferred,
  63 the system call will return \-1 with the global variable
  64 .Va errno
  65 set to
  66 .Er EINTR .
  67 Interrupted system calls that have started transferring
  68 data will return the amount of data actually transferred.
  69 System call interrupt is the signal behavior found on
  70 .Bx 4.1
  71 and
  72 .At V
  73 systems.
  74 .Pp
  75 Note that the new
  76 .Bx 4.2
  77 signal handling semantics are not
  78 altered in any other way.
  79 Most notably, signal handlers always remain installed until
  80 explicitly changed by a subsequent
  81 .Xr sigaction 2
  82 call, and the signal mask operates as documented in
  83 .Xr sigaction 2 .
  84 Programs may switch between restartable and interruptible
  85 system call operation as often as desired in the execution of a program.
  86 .Pp
  87 Issuing a
  88 .Fn siginterrupt 3
  89 call during the execution of a signal handler will cause
  90 the new action to take place on the next signal to be caught.
  91 .Sh NOTES
  92 This library routine uses an extension of the
  93 .Xr sigaction 2
  94 system call that is not available in
  95 .Bx 4.2 ;
  96 hence, it should not be used if backward compatibility is needed.
  97 .Sh RETURN VALUES
  98 .Rv -std siginterrupt
  99 .Sh ERRORS
 100 The
 101 .Fn siginterrupt
 102 call fails if:
 103 .Bl -tag -width Er
 104 .It Bq Er EINVAL
 105 The
 106 .Fa sig
 107 argument
 108 is not a valid signal number.
 109 .El
 110 .Sh SEE ALSO
 111 .Xr sigaction 2 ,
 112 .Xr sigblock 2 ,
 113 .Xr sigpause 2 ,
 114 .Xr sigsetmask 2 ,
 115 .Xr signal 3
 116 .Sh HISTORY
 117 The
 118 .Fn siginterrupt
 119 function appeared in
 120 .Bx 4.3 .