fastrm - Quickly remove a list of files


   fastrm [-de] [-c|-cI] [-s|-sM] [-u|-uN] base-directory


   fastrm 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.  fastrm does not delete files
   safely or with an eye to security, but rather cuts every corner it can
   to delete files as fast as it can.  It should therefore never be run on
   publically writable directories, or in any other environment where a
   hostile party may control the directory structure in which it is

   If a file name is not an absolute path name, it is considered to be
   relative to base-directory as given on the command line.  The base-
   directory parameter must be a simple absolute pathname (it must not
   contain multiple consecutive 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 operating
   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

   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.


       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

   -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 preceding sort(1) command,
       ensuring that fastrm will fail if the sort fails.

       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 directory 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.  However, 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.

       Specifying this option promises that there are no symbolic links in
       the directory tree from which files are being removed.  This allows
       fastrm to make an additional optimization to its calls to chdir(2),
       constructing 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 -usr", or "fastrm -user".
   These happen to often be convenient sets of options to use.


   fastrm exits with a status of zero if there were no problems, and an
   exit status of 1 if something went wrong.  Attempting to remove a file
   that does not exist is not considered a problem.


   fastrm is typically invoked by INN via expirerm(8) using a command

       fastrm -e <patharticles in inn.conf> < expire.list

   To enable all optimizations and see the affect on the order of removal
   caused by -s, use:

       fastrm -d -s -e -u <patharticles> < 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

       fastrm -e -u3 <patharticles> < expire.list

   to strongly prefer relative paths but not to use readdir(2) to order
   the calls to unlink(2).

   You may want to edit expirerm(8) to change the flags passed to fastrm.


   fastrm cuts corners and does not worry about security, so it does not
   use chdir(2) safely and could be tricked into removing files other than
   those that were intended if run on a specially constructed file tree or
   a file tree that is being modified while it is running.  It should
   therefore never be used with world-writable directories or any other
   directory that might be controlled or modified by an attacker.


   fastrm 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 possible to use fastrm outside of INN
   as a general fast file removal program.


   fastrm was originally written by <>.  This manual page
   was rewritten in POD by Russ Allbery <> for

   $Id: fastrm.pod 9767 2014-12-07 21:13:43Z iulius $




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