xref: /freebsd/lib/libc/gen/siginterrupt.3 (revision dc36d6f9bb1753f3808552f3afd30eda9a7b206a)
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28.Dd June 4, 1993
29.Dt SIGINTERRUPT 3
30.Os
31.Sh NAME
32.Nm siginterrupt
33.Nd allow signals to interrupt system calls
34.Sh LIBRARY
35.Lb libc
36.Sh SYNOPSIS
37.In signal.h
38.Ft int
39.Fn siginterrupt "int sig" "int flag"
40.Sh DESCRIPTION
41The
42.Fn siginterrupt
43function
44is used to change the system call restart
45behavior when a system call is interrupted by the specified signal.
46If the flag is false (0), then system calls will be restarted if
47they are interrupted by the specified signal
48and no data has been transferred yet.
49System call restart has been the default behavior since
50.Bx 4.2 ,
51and is the default behaviour for
52.Xr signal 3
53on
54.Fx .
55.Pp
56If the flag is true (1),
57then restarting of system calls is disabled.
58If a system call is interrupted by the specified signal
59and no data has been transferred,
60the system call will return \-1 with the global variable
61.Va errno
62set to
63.Er EINTR .
64Interrupted system calls that have started transferring
65data will return the amount of data actually transferred.
66System call interrupt is the signal behavior found on
67.Bx 4.1
68and
69.At V
70systems.
71.Pp
72Note that the new
73.Bx 4.2
74signal handling semantics are not
75altered in any other way.
76Most notably, signal handlers always remain installed until
77explicitly changed by a subsequent
78.Xr sigaction 2
79call, and the signal mask operates as documented in
80.Xr sigaction 2 .
81Programs may switch between restartable and interruptible
82system call operation as often as desired in the execution of a program.
83.Pp
84Issuing a
85.Fn siginterrupt 3
86call during the execution of a signal handler will cause
87the new action to take place on the next signal to be caught.
88.Sh NOTES
89This library routine uses an extension of the
90.Xr sigaction 2
91system call that is not available in
92.Bx 4.2 ,
93hence it should not be used if backward compatibility is needed.
94.Sh RETURN VALUES
95.Rv -std siginterrupt
96.Sh ERRORS
97The
98.Fn siginterrupt
99call fails if:
100.Bl -tag -width Er
101.It Bq Er EINVAL
102The
103.Fa sig
104argument
105is not a valid signal number.
106.El
107.Sh SEE ALSO
108.Xr sigaction 2 ,
109.Xr sigprocmask 2 ,
110.Xr sigsuspend 2 ,
111.Xr signal 3
112.Sh HISTORY
113The
114.Fn siginterrupt
115function appeared in
116.Bx 4.3 .
117