table of contents
explain_poll(3) | Library Functions Manual | explain_poll(3) |
NAME¶
explain_poll - explain poll(2) errorsSYNOPSIS¶
#include <libexplain/poll.h>DESCRIPTION¶
These functions may be used to obtain explanations for errors returned by the poll(2) system call.explain_poll¶
const char *explain_poll(struct pollfd *fds, int nfds, int timeout); The explain_poll function is used to obtain an explanation of an error returned by the poll(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be decoded.- fds
- The original fds, exactly as passed to the poll(2) system call.
- nfds
- The original nfds, exactly as passed to the poll(2) system call.
- timeout
- The original timeout, exactly as passed to the poll(2) system call.
- Returns:
- The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.
int result = poll(fds, nfds, timeout);
{
fprintf(stderr, "%s\n", explain_poll(fds, nfds, timeout));
exit(EXIT_FAILURE); }
explain_errno_poll¶
const char *explain_errno_poll(int errnum, struct pollfd *fds, int nfds, int timeout); The explain_errno_poll function is used to obtain an explanation of an error returned by the poll(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.- errnum
- The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
- fds
- The original fds, exactly as passed to the poll(2) system call.
- nfds
- The original nfds, exactly as passed to the poll(2) system call.
- timeout
- The original timeout, exactly as passed to the poll(2) system call.
- Returns:
- The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.
int result = poll(fds, nfds, timeout);
{ int err = errno;
fprintf(stderr, "%s\n", explain_errno_poll(err, fds, nfds, timeout));
exit(EXIT_FAILURE); }
explain_message_poll¶
void explain_message_poll(char *message, int message_size, struct pollfd *fds, int nfds, int timeout); The explain_message_poll function is used to obtain an explanation of an error returned by the poll(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail. The errno global variable will be used to obtain the error value to be decoded.- message
- The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
- message_size
- The size in bytes of the location in which to store the returned message.
- fds
- The original fds, exactly as passed to the poll(2) system call.
- nfds
- The original nfds, exactly as passed to the poll(2) system call.
- timeout
- The original timeout, exactly as passed to the poll(2) system call.
int result = poll(fds, nfds, timeout);
{ char message[3000];explain_message_poll(message, sizeof(message), fds, nfds, timeout);
fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); }
explain_message_errno_poll¶
void explain_message_errno_poll(char *message, int message_size, int errnum, struct pollfd *fds, int nfds, int timeout); The explain_message_errno_poll function is used to obtain an explanation of an error returned by the poll(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.- message
- The location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe.
- message_size
- The size in bytes of the location in which to store the returned message.
- errnum
- The error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno.
- fds
- The original fds, exactly as passed to the poll(2) system call.
- nfds
- The original nfds, exactly as passed to the poll(2) system call.
- timeout
- The original timeout, exactly as passed to the poll(2) system call.
int result = poll(fds, nfds, timeout);
{ int err = errno; char message[3000];explain_message_errno_poll(message, sizeof(message), err, fds, nfds, timeout);
fprintf(stderr, "%s\n", message); exit(EXIT_FAILURE); }
SEE ALSO¶
- poll(2)
- wait for some event on a file descriptor
- explain_poll_or_die(3)
- wait for some event on a file descriptor and report errors