CHASE(1)							Chase user's manual							  CHASE(1)

NAME

       chase - chase symbolic links

SYNOPSIS

       chase  [  --verbose  |  --from-file  | -f | --null | -0 | --loop-warn-threshold COUNT | -w COUNT | --loop-fail-threshold COUNT | -l COUNT |
       --disable-loop-detection | -D ] [file...]

       chase -v | --version

       chase -h | --help

DESCRIPTION

       Chase is a small utility that tracks down the name of the actual file that is truly accessed, when one hits a symbolic link.  It chases the
       link, so to speak.

       In normal operation, you give chase a name of an existing file.	The program will then show you (or, more accurately, print to the standard
       output stream) the name of the real file that the original file referred to.  It does not matter if you give the program the name of a reg-
       ular file; chase will just give you the same name back.	You can give the utility the option --verbose, in order to have it be more verbose
       in its operation.  You can also give the program a list of files from which it will read the file  names  to  be  chased  (see  the  option
       --from-file).

       I'll  give  you a good example of a case where chase is useful.	In a Debian GNU/Linux system, software installation is handled by the pro-
       gram dpkg(8).  There is a way to query dpkg(8), which package a file belongs to.  Unfortunately, this does not not grok all symlinks.  This
       is a problem, since the Debian system uses symbolic links extensively for handling several flavours of a program (say, XEmacs and GNU Emacs
       and the versions 19 and 20 of both).  Now with chase, one can determine the real file easily and then using this result as an  argument	to
       dpkg(8).  Observe:

       ajk@ugh:~$ dpkg -S `which xemacs20`
       dpkg: /usr/bin/xemacs20 not found.
       ajk@ugh:~$ dpkg -S `which xemacs20 | xargs chase`
       xemacs20-nomule: /usr/bin/xemacs-20.4-nomule
       ajk@ugh:~$

       When given multiple file names as arguments, chase will chase every one of them in order.

OPTIONS

       The following options are recognized by chase:

       --verbose
	      Chat about what is being done.

       -f, --from-file
	      Treat  the  file names on the command line as sources for names to be chased.  If this option is present, chase will read in each of
	      the files given on the command line (both a sole dash "-" and the absence of file names will be taken as meaning the standard  input
	      stream).	 Each line in the files is taken as a verbatim file name that will be chased like it had been given on the command line of
	      a run without this option.  There is no means for quoting the newline character; therefore only file names that do not contain  new-
	      lines  can  be specified via the files.  This restriction is lifted by the -0 option, though.  However, literal spaces are preserved
	      and are not interpreted as special.

       -0, --null
	      This option implies the option -f, which reads file names from a file.  The -0 option modifies the behavior -f so  that  instead	of
	      treating	lines in the file as file names, the file names are expected to be separated by null characters.  This allows for specify-
	      ing file names with newlines in them with -f.

       -w WCOUNT, --loop-warn-threshold=WCOUNT

       -l LCOUNT, --loop-fail-threshold=LCOUNT
	      Set the threshold for warning about a possible symlink loop (WCOUNT) and for failing because of one  (LCOUNT).   There  are  default
	      values, which you can find out by invoking chase with the argument --help.  Using zero as WCOUNT or LCOUNT disables the check.

       -D, --disable-loop-detection
	      Normally	chase keeps a record of all symlinks it has visited when chasing the current file.  It uses this record to reliably detect
	      symlink loops.  However, checking the record slows the process a little (more for long chains of symlinks) and the record requires a
	      small  amount of memory (more for long chains of symlinks), so it may be desirable in some cases to inhibit this check.  This option
	      disables this loop detection and the associated recording of visited symlinks.  When this option is in effect (assuming no  bugs	in
	      the related code) chase runs in constant space and linear time relative to the length of the symlink chains encountered.

       -h, --help
	      Output a usage summary and exit successfully.

       -v, --version
	      Show version information and exit successfully.

DIAGNOSTICS

       The exit status is 0 if and only if all files given in the command lines exist and none of them are dangling symlinks.

       The following messages are emitted by chase when it suspects or detects a symlink loop:

       quite many symlink hops, hope we're not looping...
	      This means that the chain of symlinks is longer than a given threshold.  This may mean that the chain is infinite (and thus contains
	      a loop somewhere).  The threshold can be specified by using the --loop-warn-threshold command line option.

       too many symlink hops, giving up...
	      This means that the chain of symlinks is longer than a given threshold.  This usually means that the chain  is  infinite	(and  thus
	      contains a loop somewhere).  The threshold can be specified by using the --loop-fail-threshold command line option.  If you see this
	      message, it means that chase has given up on that file.

       symlink loop detected, giving up...
	      The symlink chain is looping and therefore there is no result for the chase.  Chase has given up on that file.

       Additionally, Chase emits several error messages under problematic conditions.  They all come from the system libraries, so the program has
       no  control  over the actual wording of the messages.  They all follow the format "program name: file name: error message", where file name
       is the name of the offending file or directory.

BUGS

       Chase may have bugs. If you find them, please report them to <rotty@debian.org> or preferably via the Debian bugtracking system.

AUTHOR

       Chase has been written by Antti-Juhani Kaijanaho <gaia@iki.fi> and is currently maintained by Andreas Rottmann <rotty@debian.org>.

SEE ALSO

       find(1), ln(1), namei(1), readlink(1), readlink(2), symlinks(1)

Chase 0.5							    2000-01-02								  CHASE(1)