Ubuntu Manpage: buffchan - Buffered file-writing backend for INN

Provided by: inn2_2.7.2~20240212-1build3_amd64

NAME

       buffchan - Buffered file-writing backend for INN

SYNOPSIS

       buffchan [-bru] [-c lines] [-C seconds] [-d directory] [-f num-fields] [-l lines] [-L seconds] [-m map]
       [-p pid-file] [-s format]

DESCRIPTION

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 one.

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 options.

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:

!flush [site]
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 'flush 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.

!drop [site]
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".

!readmap
The map file specified with the -m option, if given, will be reloaded.

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.

OPTIONS

-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.

-c lines
If the -c flag is given, buffchan will close and reopen a file after every lines lines are written to
the file.

-C seconds
If the -C flag is given, buffchan will close and reopen a file if it has been open for more than
seconds seconds.

-d directory
By default, buffchan writes its output into the pathoutgoing directory. 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).

-f num-fields
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.

-l lines
If the -l flag is given, buffchan will flush the output after every lines lines are written to a
file.

-L seconds
If the -L flag is given, buffchan will flush each output file every seconds seconds.

-m map
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, the following map file may be used to map the short names used in the example below to
the full domain names:

# This is a comment
uunet:news.uu.net
foo:foo.com
munnari:munnari.oz.au

-p pid-file
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.

EXAMPLES

       If buffchan is invoked with "-f 2" and given the following input:

           news.software.nntp <1643@munnari.oz.au> foo uunet
           news.software.nntp <102060@litchi.foo.com> uunet munnari
           comp.sources.unix <999@news.foo.com> foo uunet munnari

       then the file foo in pathoutgoing will have these lines:

           news.software.nntp <1643@munnari.oz.au>
           comp.sources.unix <999@news.foo.com>

       the file munnari in pathoutgoing will have these lines:

           news.software.nntp <102060@litchi.foo.com>
           comp.sources.unix <999@news.foo.com>

       and the file uunet in pathoutgoing will have these lines:

           news.software.nntp <1643@munnari.oz.au>
           news.software.nntp <102060@litchi.foo.com>
           comp.sources.unix <999@news.foo.com>

       Using buffchan this way can be done in newsfeeds with for instance:

           foo:*,@misc.*:Ap,Tm:buffchan!
           munnari:*,@rec.*:Ap,Tm:buffchan!
           uunet:*:Ap,Tm:buffchan!
           buffchan!:*:Tx,WGm*:<pathbin>/buffchan -f 2

       It  will  generate  the  examples  above.   See  the "W" flag in newsfeeds(5) for how to parameterize the
       output.

HISTORY