linux epoll学习
#include <sys/time.h> /* For portability */
#include <sys/select.h>
int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);
Returns number of ready file descriptors, 0 on timeout, or –1 on error
#include <sys/select.h>
void FD_ZERO(fd_set *fdset);
void FD_SET(int fd, fd_set *fdset);
void FD_CLR(int fd, fd_set *fdset);
int FD_ISSET(int fd, fd_set *fdset);
Returns true (1) if fd is in fdset, or false (0) otherwise
FD_ZERO() initializes the set pointed to by fdset to be empty.
FD_SET() adds the file descriptor fd to the set pointed to by fdset.
FD_CLR() removes the file descriptor fd from the set pointed to by fdset.
FD_ISSET() returns true if the file descriptor fd is a member of the set pointed to
by fdset.
struct timeval {
time_t tv_sec; /* Seconds */
suseconds_t tv_usec;/* Microseconds (long int) */
};
typedef struct
{
/*XPG4.2requiresthismembername.Otherwiseavoidthename
fromtheglobalnamespace.*/
#ifdef__USE_XOPEN
__fd_maskfds_bits[__FD_SETSIZE/__NFDBITS];
#define__FDS_BITS(set)((set)->fds_bits)
#else
__fd_mask__fds_bits[__FD_SETSIZE/__NFDBITS];
#define__FDS_BITS(set)((set)->__fds_bits)
#endif
}fd_set; /* linux下为 1024/8 = 128 Bytes */
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#include <sys/epoll.h>
int epoll_create(int size);
Returns file descriptor on success, or –1 on error
Starting with kernel 2.6.27, Linux supports a new system call, epoll_create1().
This system call performs the same task as epoll_create(), but drops the obsolete
size argument and adds a flags argument that can be used to modify the behavior
of the system call. One flag is currently supported: EPOLL_CLOEXEC, which causes
the kernel to enable the close-on-exec flag (FD_CLOEXEC) for the new file descriptor.
This flag is useful for the same reasons as the open() O_CLOEXEC flag described in
Section 4.3.1
#include <sys/epoll.h>
int epoll_ctl(int epfd, int op, int fd, struct epoll_event *ev);
Returns 0 on success, or –1 on error
The fd argument identifies which of the file descriptors in the interest list is to have
its settings modified. This argument can be a file descriptor for a 'pipe, FIFO,
socket, POSIX message queue, inotify instance, terminal, device, or even another epoll
descriptor' (i.e., we can build a kind of hierarchy of monitored descriptors). However,
fd can’t be a file descriptor for a regular file or a directory (the error EPERM results).
The op argument specifies the operation to be performed, and has one of the
following values:
EPOLL_CTL_ADD
EPOLL_CTL_MOD
EPOLL_CTL_DEL
共12字节:
struct epoll_event {
uint32_t events; /* epoll events (bit mask) */
epoll_data_t data; /* User data */
};
The data field of the epoll_event structure is typed as follows:
typedef union epoll_data {
void *ptr; //Pointer to user-defined data
int fd; //File descriptor */
uint32_t u32; //32-bit integer */
uint64_t u64; //64-bit integer */
} epoll_data_t;
#include <sys/epoll.h>
int epoll_wait(int epfd, struct epoll_event *evlist, int maxevents, int timeout);
Returns number of ready file descriptors, 0 on timeout, or –1 on error
Table 63-8: Bit-mask values for the epoll events field Bit
EPOLLIN Data other than high-priority data can be read
EPOLLPRI High-priority data can be read
EPOLLRDHUP Shutdown on peer socket (since Linux 2.6.17)
EPOLLOUT Normal data can be written
EPOLLET Employ edge-triggered event notification
EPOLLONESHOT Disable monitoring after event notification
EPOLLERR An error has occurred
EPOLLHUP A hangup has occurred
Input to Returned by
epoll_ctl()? epoll_wait()?
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// gcc epoll_input_fifo.c lib/error_functions.c lib/get_num.c -Ilib -o epoll_input_fifo.out
#include <sys/epoll.h>
#include <fcntl.h>
#include "tlpi_hdr.h"
#define MAX_BUF 1000
#define MAX_EVENTS 5
int main(int argc, char *argv[]){
int epfd, ready, fd, s, j, numOpenFds;
struct epoll_event ev;
struct epoll_event evlist[MAX_EVENTS];
char buf[MAX_BUF];
printf("EPOLLIN: 0x%x\n", EPOLLIN);
printf("EPOLLHUP: 0x%x\n", EPOLLHUP);
printf("EPOLLERR: 0x%x\n", EPOLLERR);
if (argc < 2 || strcmp(argv[1], "--help") == 0)
usageErr("%s file...\n", argv[0]);
epfd = epoll_create(argc-1);
if(epfd == -1)
errExit("epoll_create");
for(j = 1; j < argc; j++){
fd = open(argv[j], O_RDONLY);
if(fd == -1){
errExit("open");
}
printf("Opened '%s' on fd %d\n", argv[j], fd);
ev.events = EPOLLIN; // Only interested in input events
ev.data.fd = fd;
if(epoll_ctl(epfd, EPOLL_CTL_ADD, fd, &ev) == -1)
errExit("epoll_ctl");
}
numOpenFds = argc - 1;
while(numOpenFds > 0){
printf("About to epoll_wait()\n");
ready = epoll_wait(epfd, evlist, MAX_EVENTS, -1);
if(ready == -1){
if(errno == EINTR)
continue;
else
errExit("epoll_wait");
}
printf("Ready: %d\n", ready);
for(j=0;j<ready;j++){
printf(" fd=%d; events: %s%s%s\n", evlist[j].data.fd,
(evlist[j].events & EPOLLIN) ? "EPOLLIN " : "",
(evlist[j].events & EPOLLHUP) ? "EPOLLHUP " : "",
(evlist[j].events & EPOLLERR) ? "EPOLLERR " : "");
if(evlist[j].events & EPOLLIN){
s = read(evlist[j].data.fd, buf, MAX_BUF);
if(s == -1)
errExit("read");
printf(" read %d bytes: %.*s\n", s,s,buf);
} else if(evlist[j].events & (EPOLLHUP | EPOLLERR)) {
printf(" closing fd %d\n", evlist[j].data.fd);
if(close(evlist[j].data.fd)==-1)
errExit("close");
numOpenFds--;
}
}
}
printf("All file descriptors closed. bye\n");
exit(EXIT_SUCCESS);
}
from: 《The Linux Programming Interface》P1355
