FASTRM(1) InterNetNews Documentation FASTRM(1)NAMEfastrm - Quickly remove a list of files
SYNOPSISfastrm [-de] [-u|-uN] [-s|-sM] [-c|-cI] base-directory
DESCRIPTIONfastrm reads a list of either file names or storage API
tokens, one per line, from its standard input and removes
them. Storage API tokens are removed via the SMcancel()
interface.
If a file name is not an absolute path name, it is consid
ered to be relative to base-directory as given on the com
mand line. The base-directory parameter must be a simple
absolute pathname (it must not contain multiple consecu
tive slashes or references to the special directories "."
or "..").
fastrm is designed to be faster than the typical "| xargs
rm" pipeline when given a sorted list of file names as
input. For example, fastrm will usually chdir(2) into a
directory before removing files from it, meaning that if
its input is sorted, most names passed to unlink(2) will
be simple names. This can substantially reduce the oper
ating system overhead from directory lookups.
fastrm assumes that its input is valid and that it is safe
to call unlink(2) on every file name it is given. As a
safety measure, however, fastrm when running as root will
check with stat(2) that a file name doesn't specify a
directory before removing it. (In some operating systems,
root is allowed to unlink directories, even directories
which aren't empty, which can cause file system corrup
tion.)
The input to fastrm should always be sorted -- or even
better be in the order file names are output by find(1)--
if speed is an issue and the input isn't solely storage
API tokens. (It deals fine with unsorted input, but is
unlikely to be any faster in that case than a simple
"xargs rm" command.) Sorting may even slightly speed up
the removal of storage API tokens due to caching effects,
since sorting will tend to keep all of the tokens from a
particular storage method together.
Various additional optimizations for removing files can be
turned on and/or tuned with options (see below). Which
options will be most effective depends heavily on the
underlying structure of the file system, the way in which
directories are stored and searched, and similar often
underdocumented operating system implementation details.
The more sophisticated the underlying operating system and
file system, the more likely that it will already perform
the equivalent of these optimizations internally.
OPTIONS-d Don't remove any files. Instead, print a list of the
files that would be removed to standard output. Each
line contains either the current directory of fastrm
at the time it would do the unlink and the relative
path name it would pass to unlink(2) as two fields
separated by whitespace and a "/", the absolute path
name (as a single field) that would be passed to
unlink(2), or the string "Token" and the storage API
token that would be removed.
-e Treat an empty input file as an error. This is most
useful when fastrm is last in a pipeline after a pre
ceding sort(1) command, ensuring that fastrm will fail
if the sort fails.
-cI Controls when fastrm calls chdir(2). If the number of
files to be unlinked from a given directory is at
least I, then fastrm will change to that directory
before unlinking those files. Otherwise, it will use
either the absolute path names or a path name relative
to the current directory (whichever is likely more
efficient). The I parameter is optional; if just -c
is given, -c1 is assumed, which will cause fastrm to
always chdir before calling unlink(2). The default is
-c3. Use -c0 to prevent fastrm from ever using
chdir(2).
-sM When -s is given and the number of files to remove in
a directory is greater than M, rather than remove
files in the order given, fastrm will open the direc
tory and read it, unlinking files in the order that
they appear in the directory. On systems with a per-
process directory cache or that use a linear search to
find files in a directory, this should make directory
lookups faster. The M parameter is optional; if just
-s is given, -s5 is assumed.
When this option is in effect, fastrm won't attempt to
remove files that it doesn't see in the directory,
possibly significantly speeding it up if most of the
files to be removed have already been deleted. How
ever, using this option requires fastrm to do more
internal work and it also assumes that the order of
directory listings is stable in the presence of calls
to unlink(2) between calls to readdir(3). This may be
a dangerous assumption with some sophisticated file
systems (and in general this option is only useful
with file systems that use unindexed linear searches
to find files in directories or when most of the files
to be removed have already been deleted).
This optimization is off by default.
-uN Specifying this option promises that there are no sym
bolic links in the directory tree from which files are
being removed. This allows fastrm to make an addi
tional optimization to its calls to chdir(2), con
structing a relative path using "../.." and the like
to pass to chdir(2) rather than always using absolute
paths. Since this reduces the number of directory
lookups needed with deeply nested directory structures
(such as that typically created by traditional news
spool storage), it can be a significant optimization,
but it breaks horribly in the presence of symbolic
links to directories.
When -u is given, fastrm will use at most N levels of
".." segments to construct paths. N is optional; if
just -u is given, -u1 is assumed.
This optimization is off by default.
fastrm also accepts -a and -r options, which do nothing at
all except allow you to say "fastrm -usa", "fastrm -ussr",
or "fastrm -user". These happen to often be convenient
sets of options to use.
EXIT STATUSfastrm exits with a status of zero if there were no prob
lems, and an exit status of 1 if something went wrong.
Attempting to remove a file that does not exist is not
considered a problem.
EXAMPLESfastrm is typically invoked by INN via expirerm(8) using a
command like:
fastrm-e /usr/local/news/spool/articles < expire.list
To enable all optimizations and see the affect on the
order of removal caused by -s, use:
fastrm-d -s -e -u ~news/spool/articles < expire.list
If your file system has indexed directory lookups, but you
have a deeply nested directory structure, you may want to
use a set of flags like:
fastrm-e -u3 ~news/spool/articles < expire.list
to strongly prefer relative paths but not to use read_
dir(2) to order the calls to unlink(2).
You may want to edit expirerm(8) to change the flags
passed to fastrm.
NOTESfastrm defers opening the storage subsystem or attempting
to parse any INN configuration files until it encounters a
token in the list of files to remove. It's therefore pos
sible to use fastrm outside of INN as a general fast file
removal program.
HISTORYfastrm was originally written by kre@munnari.oz.au. This
manual page rewritten in POD by Russ Allbery <rra@stan
ford.edu> for InterNetNews.
$Id: fastrm.1,v 1.1.2.1 2001/02/03 07:38:44 rra Exp $
SEE ALSOexpirerm(8)2001-02-02 INN 2.3.2 FASTRM(1)
