buffchan - Buffered file-writing backend for INN
buffchan [-bru] [-c lines] [-C seconds] [-d directory] [-f num-fields]
[-l lines] [-L seconds] [-m map] [-p pid-file] [-s format]
buffchan reads lines from standard input and copies the initial fields
in each line to the files named by the remaining fields on the line.
buffchan is intended to be called by innd as an exploder feed.
The input is interpreted as a sequence 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 and
do not contain any whitespace. The default number of initial fields is
For each line of input, buffchan writes the initial fields, separated
by a space and followed by a newline, to each of the files named in the
filename fields. The output files are kept open and are only flushed
or closed based on the schedule given by the -c, -C, -l, and -L
As an exploder feed (see newsfeeds(5) for an explanation), buffchan
interprets lines beginning with an exclamation point as commands.
Besides "!begin" (which only marks the start of the feed), there are
three supported commands:
The flush command closes and reopens all open files. An optional
site can be specified, in which case buffchan flushes only that
file. This command is analogous to the "ctlinnd flush" command.
This command can be sent via innd using "ctlinnd send buffchan-site
Applications can tell that flush has completed by renaming the file
before issuing the command. When the original file name has
reappeared, the flush is complete. If fchmod(3) is available,
buffchan also changes the file to read-only while it’s actively
writing to it and changes it back to read/write once it has been
closed. It will change the mode back to read-only only if it
reopens the same file.
The drop command is similar to the flush command, except that no
files are reopened. If given an argument, only the specified site
is dropped; otherwise, all sites are dropped. (Note that a site
will be restarted if the input stream mentions the site again.)
When a "ctlinnd drop site" command is sent, innd will automatically
forward the command to buffchan if the site is listed as a funnel
feeding into the buffchan exploder. To drop all sites, use
"ctlinnd send buffchan-site drop".
The map file specified with the -m option, if given, will be
Once buffchan opens a file, it keeps it open (in the absence of a drop
command). The input must therefore never specify more files than the
maximum number of files a process may open.
-b Force the output to be buffered. (This is generally the default,
but it may depend on the operating system.) If -b is given, a
buffer size of BUFSIZ (a constant of the system standard I/O
library) is used.
If the -c flag is given, buffchan will close and reopen a file
after every lines lines are written to the file.
If the -C flag is given, buffchan will close and reopen a file if
it has been open for more than seconds seconds.
This flag may be used to specify a directory the program should
change to before starting. If this flag is used, the default for
the -s flag (see below) is changed to be a simple %s (in other
words, output files are considered to be relative to directory).
By default, each line is expected to contain one fixed field
followed by some number of filename fields. If this flag is given,
num-fields will be used as the number of initial fixed fields.
If the -l flag is given, buffchan will flush the output after every
lines lines are written to a file.
If the -L flag is given, buffchan will flush each output file every
Map files translate the names in the filename fields on each line
into filenames that should be used instead. It’s used primarily
when short names are used in newsfeeds, but the output files should
use the full domain names of remote peers.
In the map file, blank lines and lines starting with a number sign
("#") are ignored. All other lines should have two host names
separated by a colon. The first field is the name that may appear
in the input stream; the second field names the file to be used
when the name in the first field appears. For example:
# This is a comment
If the -p option is given, buffchan will write a line containing
its process ID (in text) to the specified file when it starts.
-r By default, buffchan sends its error messages to pathlog/errlog.
To suppress this redirection and send error messages to standard
error, use the -r flag.
-s The -s flag may be used to specify a format that maps a filename
from the filename fields at the end of each line to an actual
filename. This is a sprintf(3) format string that should contain a
single instance of %s, which will be replaced with the value of the
filename field (possibly after mapping with the map file from -m).
The default value is pathoutgoing/%s.
-u If the -u flag is used, the output will be unbuffered.
If buffchan is invoked with "-f 2" and given the following input:
news/software/b/132 <email@example.com> foo uunet
news/software/b/133 <firstname.lastname@example.org> uunet munnari
comp/sources/unix/2002 <email@example.com> foo uunet munnari
Then the file foo will have these lines:
the file munnari will have these lines:
and the file uunet will have these lines:
Written by Rich $alz <firstname.lastname@example.org> for InterNetNews. Converted
to POD by Russ Allbery <email@example.com>.
$Id: buffchan.pod 7851 2008-05-26 19:33:08Z iulius $
ctlinnd(8), filechan(8), inn.conf(5), innd(8), newsfeeds(5).