10.13 sigpending function

The function sigpending is blocked and the process that is currently called by the function hangs the signal set, which is returned by the parameter set.

1. #include<signal.h>
2. int sigpending(sigset_t*set);
3. Returns:0if OK,-1 on error.

Example

2. #include"apue.h"
4. staticvoid sig_quit(int);
8. int main(void)
10. {
12. sigset_t newmask,oldmask,pendmask;
16. if(signal(SIGQUIT, sig_quit)== SIG_ERR)
18. err_sys("can‘t catch SIGQUIT");
22. /*
24. * Block SIGQUIT and save current signal mask
26. *
28. */
30. sigemptyset(&newmask);
32. sigaddset(&newmask, SIGQUIT);
34. if(sigprocmask(SIG_BLOCK,&newmask,&oldmask)<0)
36. err_sys("SIG_BLOCK error");
40. sleep(5);/*SIGOUT here will remain pending*/
44. if(sigpending(&pendmask)<0)
46. err_sys("sigpending error");
48. if(sigismember(&pendmask, SIGQUIT))
50. printf("\nSIGQUIT pending\n");
54. /*
56. * Restore signal mask whick unblocks SIGQUIT.
58. */
60. if(sigprocmask(SIG_SETMASK,&oldmask, NULL)<0)
62. err_sys("SIG_SETMASK error");
66. printf("SIGQUIT unblocked\n");
70. sleep(5);/*SIGQUIT here will terminate with core file */
72. exit(0);
74. }
78. staticvoid sig_quit(int signo)
80. {
82. printf("caught SIGQUIT\n");
84. if(signal(SIGQUIT, SIG_DFL)== SIG_ERR)
86. err_sys("can‘t reset SIGQUIT");
88. }

Execution effects such as:

2. [email protected]:~/UnixProgram/Chapter10$./10_15.exe
4. ^\^\^\
6. SIGQUIT pending
8. caught SIGQUIT
10. SIGQUIT unblocked
12. ^\Quit
14. [email protected]:~/UnixProgram/Chapter10$./10_15.exe
16. SIGQUIT unblocked
18. [email protected]:~/UnixProgram/Chapter10$

From for notes (Wiz)

10.13 sigpending function