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Annotation of 43BSDTahoe/man/man3f/signal.3, revision 1.1.1.1

1.1       root        1: .\" Copyright (c) 1983 Regents of the University of California.
                      2: .\" All rights reserved.  The Berkeley software License Agreement
                      3: .\" specifies the terms and conditions for redistribution.
                      4: .\"
                      5: .\"    @(#)signal.3f   6.1 (Berkeley) 5/15/85
                      6: .\"
                      7: .TH SIGNAL 3F "May 15, 1985"
                      8: .UC 5
                      9: .SH NAME
                     10: signal \- change the action for a signal
                     11: .SH SYNOPSIS
                     12: .B integer function signal(signum, proc, flag)
                     13: .br
                     14: .B integer signum, flag
                     15: .br
                     16: .B external proc
                     17: .SH DESCRIPTION
                     18: When a process incurs a signal (see
                     19: .IR signal (3C))
                     20: the default action
                     21: is usually to clean up and abort.
                     22: The user may choose to write an alternative signal handling routine.
                     23: A call to
                     24: .I signal
                     25: is the way this alternate action is specified to the system.
                     26: .PP
                     27: .I Signum
                     28: is the signal number (see
                     29: .IR signal (3C)).
                     30: If
                     31: .I flag
                     32: is negative, then
                     33: .I proc
                     34: must be the name of the user signal handling routine.
                     35: If
                     36: .I flag
                     37: is zero or positive, then
                     38: .I proc
                     39: is ignored and the value of
                     40: .I flag
                     41: is passed to the system as the signal action definition.
                     42: In particular, this is how previously saved signal actions can be restored.
                     43: Two possible values for
                     44: .I flag
                     45: have specific meanings:
                     46: 0 means "use the default action" (See NOTES below),
                     47: 1 means "ignore this signal".
                     48: .PP
                     49: A positive returned value is the previous action definition.
                     50: A value greater than 1 is the address of a routine that
                     51: was to have been called on occurrence of the given signal.
                     52: The returned value can be used in subsequent calls to
                     53: .I signal
                     54: in order to restore a previous action definition.
                     55: A negative returned value is the negation of a system error code.
                     56: (See
                     57: .IR perror (3F))
                     58: .SH FILES
                     59: .ie \nM /usr/ucb/lib/libU77.a
                     60: .el /usr/lib/libU77.a
                     61: .SH "SEE ALSO"
                     62: signal(3C), kill(3F), kill(1)
                     63: .SH NOTES
                     64: .B f77
                     65: arranges to trap certain signals when a process is started.
                     66: The only way to restore the default
                     67: .B f77
                     68: action is to save the returned
                     69: value from the first call to
                     70: .I signal.
                     71: .PP
                     72: If the user signal handler is called, it will be passed the signal number
                     73: as an integer argument.

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