fastrm - Quickly remove a list of files


SYNOPSIS

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


DESCRIPTION

       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.

       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



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).


       -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 STATUS

       fastrm 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.


EXAMPLES

       fastrm 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
       readdir(2) to order the calls to unlink(2).

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

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


HISTORY

       fastrm 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 ALSO

       expirerm(8)


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