diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 51 |
1 files changed, 51 insertions, 0 deletions
@@ -25289,6 +25289,57 @@ holds the write end. If the function fails, it throws an exception of type .codn file-error . +.coNP Function @ poll +.synb +.mets (poll < poll-list <> [ timeout ]) +.syne +.desc +The +.code poll +function suspends execution while monitoring one or more file descriptors +for specified events. It is a wrapper for the same-named POSIX function. + +The +.meta poll-list +argument is a list of +.code cons +pairs. The +.code car +of each pair is either an integer file descriptor, or else a stream +object which has a file descriptor (the +.code fileno +function can be applied to that stream to retrieve a descriptor). +The +.code cdr +of each pair is an integer bit mask specifying the events, whose +occurrence the file descriptor is to be monitored for. The variables +.codn poll-in , +.codn poll-out , +.code poll-err +and several others are available which hold bitmask values corresponding +to the constants +.codn POLLIN , +.codn POLLOUT , +.code POLLERR +used with the C language +.code poll +function. + +The +.meta timeout +argument, if absent, defaults to the value -1, which specifies an indefinite +wait. A nonnegative value specifies a wait with a timeout, measured in +milliseconds. + +The function returns a list of pairs representing the descriptors or streams +which were successfully polled. If the function times out, it returns an +empty list. If an error occurs, an exception is thrown. + +The returned list is similar in structure to the input list. However, it holds +only entries which polled positive. The +.code cdr +of every pair now holds a bitmask of the events which were to have occurred. + .SS* Unix Itimers Itimers ("interval timers") can be used in combination with signal handling to execute asynchronous actions. Itimers deliver delayed, one-time signals, |