eventfdman

EXAMPLE

The following program creates an eventfd file descriptor and then forks tocreate a child process. While the parent briefly sleeps, the child writeseach of the integers supplied in the program&＃39;s command-line arguments to theeventfd file descriptor. When the parent has finished sleeping, it reads fromthe eventfd file descriptor.

The following shell session shows a sample run of the program:

 $ ./a.out 1 2 4 7 14 

 Child writing 1 to efd 

 Child writing 2 to efd 

 Child writing 4 to efd 

 Child writing 7 to efd 

 Child writing 14 to efd 

 Child completed write loop 

 Parent about to readParent read 28 (0x1c) from efd

Program source

#include  

#include  

#include

#include  

#include  

 #define handle_error(msg) \ 

 do { perror(msg); exit(EXIT_FAILURE); } while (0) 

 intmain(int argc, char *argv[]) 

 {int efd, j; 

 uint64_t u; 

 ssize_t s; 

 if (argc <2) 

{ 

 fprintf(stderr, "Usage: %s ...\n", argv[0]); 

 exit(EXIT_FAILURE); 

 } 

 efd &＃61; eventfd(0, 0);

 if (efd &＃61;&＃61; -1)handle_error("eventfd"); 

 switch (fork()) 

{ 

 case 0: 

 for (j &＃61; 1; j

{ 

 printf("Child writing %s to efd\n", argv[j]);

 u &＃61; strtoull(argv[j], NULL, 0); 

 s &＃61; write(efd, &u, sizeof(uint64_t)); 

 if (s !&＃61; sizeof(uint64_t)) 

 handle_error("write"); 

 } 

 printf("Child completed write loop\n"); 

 exit(EXIT_SUCCESS); 

 default:

 sleep(2); 

 printf("Parent about to read\n"); 

 s &＃61; read(efd, &u, sizeof(uint64_t));

 if (s !&＃61; sizeof(uint64_t)) 

 handle_error("read"); 

 printf("Parent read %llu (0x%llx) from efd\n",(unsigned long long) u, (unsigned long long) u); 

 exit(EXIT_SUCCESS); 

 case -1: 

 handle_error("fork"); 

 }

 }