Buffered file-writing backend for internetnews
buffchan [ -b ] [ -c lines ] [ -C seconds ] [ -d directory ] [ -f fields ] [ -m map ] [ -p pidfile ] [ -l lines ] [ -L seconds ] [ -r ] [ -s file_format ] [ -u ]
Buffchan reads lines from standard input and copies certain fields in each line into files named by other fields within the line. Buffchan is intended to be called by innd(8) as an exploder feed.
Once buffchan opens a file it keeps it open. The input must therefore never specify more files than can the number of available descriptors can keep open. If the ``-b'' flag is used, the program will allocate a buffer and attach it to the file using setbuf(3).
If the ``-c'' flag is used with a number n, then buffchan will close, and re-open, a file after every n lines are written to a file.
Similarly, the ``-C'' flag may be used to specify that all files should be closed and re-opened every n seconds.
The ``-d'' flag may be used to specify a directory the program should change to before starting. If this flag is used, then the default for the ``-s'' flag is changed to be a simple ``%s.''
Buffchan input is interpreted as a set of lines. Each line contains a fixed number of initial fields, followed by a variable number of filename fields. All fields in a line are separated by whitespace. The default number of initial fields is one; the ``-f'' flag may be used to specify a different number of fields. See filechan(8) for an example.
If the ``-p'' flag is used, the program will write a line containing its process ID (in text) to the specified file.
If the ``-l'' flag is used with a number n, then buffchan will call fflush(3) after every n lines are written to a file.
If the ``-L'' flag is used with a number n, then all files will be flushed every n seconds.
By default, the program sets its standard error to /var/log/news/errlog. To suppress this redirection, use the ``-r'' flag.
After the initial fields, each remaining field names a file to write. The ``-s'' flag may be used to specify a format string that maps the field to a file name. This is a sprintf(3) format string which should have a single ``%s'' parameter which will be given the field. The default value is /var/spool/news/out.going/%s. See the description of this flag in filechan(8).
If the ``-u'' flag is used, the program will request unbuffered output.
Buffchan can be invoked as an exploder feed (see newsfeeds(5)). As such, if a line starts with an exclamation point it will be treated as a command. There are three commands, described below:
The ``flush'' command closes and re-opens all open files; ``flush xxx'' which flushes only the specified site. These are analogous to the ctlinnd(8) ``flush'' command, and can be achieved by doing a ``send "flush xxx"'' command. Applications can tell that the ``flush'' has completed by renaming the file before issuing the command; buffchan has completed the command when the original filename re-appears.
The ``drop'' command is similar to the ``flush'' command except that any files are not re-opened. If given an argument, then the specified site is dropped, otherwise all sites are dropped. (Note that the site will be restarted if the input stream mentions the site.) When a ctlinnd ``drop site'' command is sent, innd will automatically forward the command to buffchan if the site is a funnel that feeds into this exploder. To drop all sites, use the ctlinnd ``send buffchan-site drop'' command.
The map file (specified with the ``-m'' flag) is reloaded.
Written by Rich $alz <[email protected]> for InterNetNews. This is revision \$3, dated \$4.