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| author | Jacob McDonnell <jacob@jacobmcdonnell.com> | 2026-04-25 19:55:15 -0400 |
|---|---|---|
| committer | Jacob McDonnell <jacob@jacobmcdonnell.com> | 2026-04-25 19:55:15 -0400 |
| commit | 253e67c8b3a72b3a4757fdbc5845297628db0a4a (patch) | |
| tree | adf53b66087aa30dfbf8bf391a1dadb044c3bf4d /static/netbsd/man2/rfilter.2 | |
| parent | a9157ce950dfe2fc30795d43b9d79b9d1bffc48b (diff) | |
docs: Added All NetBSD Manuals
Diffstat (limited to 'static/netbsd/man2/rfilter.2')
| -rw-r--r-- | static/netbsd/man2/rfilter.2 | 117 |
1 files changed, 117 insertions, 0 deletions
diff --git a/static/netbsd/man2/rfilter.2 b/static/netbsd/man2/rfilter.2 new file mode 100644 index 00000000..5a30d2dd --- /dev/null +++ b/static/netbsd/man2/rfilter.2 @@ -0,0 +1,117 @@ +$NetBSD: rfilter.2,v 1.4 2020/03/22 23:24:08 gutteridge Exp $ + +Advanced rfilter usage: the strip key, and cmd:// notation + + +1. The strip key + +All examples so far have had a match field of foo/, and have +subsequently stripped out foo/ from the path before calling the +designated program. This example shows how to not strip, if +desired. + +Remember that the third parameter in a configuration specifies +the leading pathname component to strip (the ``strip key'' in my +nomenclature). This must match the leading characters in the +path, otherwise no stripping is done. To see the difference +between stripping and no stripping, use the following +configuration (or rfilter.2.conf): + + echo/ rfilter echo/ echo %s + echo_nostrip/ rfilter no_strip echo %s + +Mount, and try a few things: + + % mkdir portal + + % mount_portal /usr/share/examples/mount_portal/rfilter.2.conf `pwd`/portal + + % cat portal/echo/"Hello there." + Hello there. + + % cat portal/echo_nostrip/"Hello there." + echo_nostrip/Hello there. + +Notice that in the second case, the full path name (after +removing the mountpoint) was substituted for %s, and not just the +portion beyond the match key. + + +2. cmd://, and how it can cause problems + +With the proliferation of the web, URLs like +http://host/path/path and ftp://host/path/path, +gopher://host/path, etc. have become common. We can provide web +access through the file system by parsing such names, and +treating them appropriately. Use rfilter.2.conf, in particular, +the following lines: + + ftp:// rfilter nostrip ftp -Vo - %s + http:// rfilter nostrip ftp -Vo - %s + +Now, access the web! + + % mount_portal /usr/share/examples/mount_portal/rfilter.2.conf `pwd`/portal + + % cksum portal/http://www.NetBSD.org/ + 362001418 6920 portal/http://www.NetBSD.org/ + + % more portal/http://www.NetBSD.org/ + <html> + <head> + <!-- Copyright (c) 1996, 1997, 1998, 1999 + The NetBSD Foundation, Inc. ALL RIGHTS RESERVED. --> + ... + +Similarly, we can access ftp sites via ftp:// + + % cat portal/ftp://ftp.NetBSD.org/pub/NetBSD/.message + GIVEN THE NATURE OF THE SOFTWARE MADE AVAILABLE UNDER THIS PROGRAM + IT IS HEREBY NOTED THAT ALL SOFTWARE, WITH THE EXCEPTION ... + + +The difficulty with the URL format becomes clear if we try to tar +a file from ftp://...: + + % tar tzf portal/ftp://ftp.NetBSD.org/pub/NetBSD-current/tar_files/doc.tar.gz + portal/ftp: Unknown host + tar (child): can't open archive portal/ftp://ftp.NetBSD.org/pub/NetBSD-current/tar_files/doc.tar.gz : Input/output error + +The problem is, when tar sees a file of the form A:B, it assumes +A is a hostname. In this case, A is "portal/ftp", which is +obviously not a hostname. + +If we want to avoid this problem, there are at least two +solutions: + 1. cat portal/ftp://ftp.NetBSD.org/pub/NetBSD-current/tar_files/doc.tar.gz | tar tzf - + + 2. Use ftp%// in the configuration file: + + ftp%// rfilter ftp%// ftp -Vo - ftp://%s + + % tar tzf portal/ftp%//ftp.NetBSD.org/pub/NetBSD-current/tar_files/doc.tar.gz + +Note that in this case, we strip out ftp%//, and prepend ftp:// +to the path argument to ftp. + +tar is not the only application which treats a colon specially -- +some others include dump, restore, and rcp/scp. For this reason, +it is recommended to use %, rather than :, for URL-like cmd%// +portal configurations. + + +3. Guru usage + +We conclude this file with an outlandish example showing the full +utility of the rfilter portal. Assume we want a single command +that can extract files from a bzip2'd tar archive that is on +an ftp site. Currently, tar does not understand bzip2 format, so +it requires at least 3 commands: + 1. fetch from ftp site + 2. bunzip2 the file + 3. extract. + +With appropriate portal configurations, the following single command +would also work. + +tar xf portal/bzcat%//`pwd`/portal/ftp%//FTP.SITE.NET/path/path/tar.bz2 |