sighold(3c) - osol9

1signal(3C)               Standard C Library Functions               signal(3C)
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NAME

6       signal,  sigset,  sighold,  sigrelse,  sigignore, sigpause - simplified
7       signal management for application processes
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SYNOPSIS

10       #include <signal.h>
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12       void (*signal(int sig, void (*disp)(int)))(int);
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15       void (*sigset(int sig, void (*disp)(int)))(int);
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18       int sighold(int sig);
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21       int sigrelse(int sig);
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24       int sigignore(int sig);
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27       int sigpause(int sig);
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DESCRIPTION

31       These functions provide simplified signal  management  for  application
32       processes.  See  signal.h(3HEAD)  for  an explanation of general signal
33       concepts.
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36       The signal() and sigset() functions modify signal dispositions. The sig
37       argument  specifies  the signal, which may be any signal except SIGKILL
38       and  SIGSTOP. The disp argument  specifies  the  signal's  disposition,
39       which  may  be SIG_DFL, SIG_IGN, or the address of a signal handler. If
40       signal() is used, disp is the address of a signal handler, and  sig  is
41       not   SIGILL,  SIGTRAP,  or  SIGPWR, the system first sets the signal's
42       disposition  to   SIG_DFL  before  executing  the  signal  handler.  If
43       sigset()  is used and disp is the address of a signal handler, the sys‐
44       tem adds sig to the calling process's signal  mask before executing the
45       signal  handler;  when  the signal handler returns, the system restores
46       the calling process's signal mask to its state prior to the delivery of
47       the  signal.  In  addition,  if  sigset()  is used and disp is equal to
48       SIG_HOLD, sig is added to the calling process's  signal  mask  and  the
49       signal's disposition remains unchanged.
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52       The sighold() function adds sig to the calling process's signal mask.
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55       The  sigrelse()  function removes sig from the calling process's signal
56       mask.
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59       The sigignore() function sets the disposition of sig to  SIG_IGN.
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62       The sigpause() function removes sig from the calling  process's  signal
63       mask  and suspends the calling process until a signal is received.
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RETURN VALUES

66       Upon successful completion, signal() returns the signal's previous dis‐
67       position. Otherwise, it returns  SIG_ERR and sets errno to indicate the
68       error.
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71       Upon successful completion, sigset() returns SIG_HOLD if the signal had
72       been blocked or the signal's previous disposition if it  had  not  been
73       blocked.  Otherwise, it returns  SIG_ERR and sets errno to indicate the
74       error.
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77       Upon successful completion,  sighold(),  sigrelse(),  sigignore(),  and
78       sigpause(),  return   0.  Otherwise,  they return  −1 and set  errno to
79       indicate the error.
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ERRORS

82       These functions fail if:
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84       EINTR     A signal was caught during the execution sigpause().
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87       EINVAL    The value of the sig argument is not a  valid  signal  or  is
88                 equal to  SIGKILL or  SIGSTOP.
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USAGE

92       The  sighold()  function  used  in  conjunction with sigrelse() or sig‐
93       pause() may be used to establish critical regions of code that  require
94       the delivery of a signal to be temporarily deferred.
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97       If signal() or sigset() is used to set  SIGCHLD's disposition to a sig‐
98       nal handler, SIGCHLD will not be sent when the calling process's  chil‐
99       dren are stopped or continued.
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102       If  any of the above functions are used to set SIGCHLD's disposition to
103       SIG_IGN, the calling process's child processes will not  create  zombie
104       processes  when  they  terminate  (see exit(2)). If the calling process
105       subsequently waits for its children, it blocks until all of  its  chil‐
106       dren  terminate;  it  then  returns  −1  with  errno set to ECHILD (see
107       wait(3C) and waitid(2)).
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110       The system guarantees that if more than one instance of the same signal
111       is  generated  to  a process, at least one signal will be received.  It
112       does not guarantee the reception of every generated signal.
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ATTRIBUTES

115       See attributes(5) for descriptions of the following attributes:
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120       ┌─────────────────────────────┬─────────────────────────────┐
121       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
122       ├─────────────────────────────┼─────────────────────────────┤
123       │Interface Stability          │Standard                     │
124       ├─────────────────────────────┼─────────────────────────────┤
125       │MT-Level                     │MT-Safe                      │
126       └─────────────────────────────┴─────────────────────────────┘
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