Test unstowing an already unstowed package

[gnu-stow.git] / stow.8

.TH STOW 8 "28 March 1998"
.SH NAME
stow \- software package installation manager
.SH SYNOPSIS
.B stow
.RI [ options ]
.IR package ...
.SH DESCRIPTION
This manual page describes GNU Stow 1.3.3, a program for managing the
installation of software packages. This is not the definitive
documentation for stow; for that, see the info manual.
.PP
Stow is a tool for managing the installation of multiple software
packages in the same run-time directory tree. One historical difficulty
of this task has been the need to administer, upgrade, install, and
remove files in independent packages without confusing them with other
files sharing the same filesystem space. For instance, it is common to
install Perl and Emacs in
.IR /usr/local .
When one does so, one winds up
(as of Perl 4.036 and Emacs 19.22)
with the following files in
.IR /usr/local/man/man1 :
.IR a2p.1 ;
.IR ctags.1 ;
.IR emacs.1 ;
.IR etags.1 ;
.IR h2ph.1 ;
.IR perl.1 ;
and
.IR s2p.1 .
Now
suppose it's time to uninstall Perl. Which man pages get removed?
Obviously
.I perl.1
is one of them, but it should not be the
administrator's responsibility to memorize the ownership of individual
files by separate packages.
.PP
The approach used by Stow is to install each package into its own
tree, then use symbolic links to make it appear as though the files are
installed in the common tree. Administration can be performed in the
package's private tree in isolation from clutter from other packages.
Stow can then be used to update the symbolic links. The structure of
each private tree should reflect the desired structure in the common
tree; i.e. (in the typical case) there should be a
.I bin
directory
containing executables, a
.I man/man1
directory containing section 1 man
pages, and so on.
.PP
Stow was inspired by Carnegie Mellon's Depot program, but is
substantially simpler and safer. Whereas Depot required database files
to keep things in sync, Stow stores no extra state between runs, so
there's no danger (as there was in Depot) of mangling directories when
file hierarchies don't match the database. Also unlike Depot, Stow will
never delete any files, directories, or links that appear in a Stow
directory (e.g.,
.IR /usr/local/stow/emacs ),
so it's always possible to
rebuild the target tree (e.g.,
.IR /usr/local ).
.SH TERMINOLOGY
A ``package'' is a related collection of files and directories that
you wish to administer as a unit--e.g., Perl or Emacs--and that needs
to be installed in a particular directory structure--e.g., with
.IR bin ,
.IR lib ,
and
.I man
subdirectories.
.PP
A ``target directory'' is the root of a tree in which one or more
packages wish to
.B appear
to be installed. A common, but by no means
the only such location is
.IR /usr/local .
The examples in this manual page
will use
.I /usr/local
as the target directory.
.PP
A ``stow directory'' is the root of a tree containing separate
packages in private subtrees. When Stow runs, it uses the current
directory as the default stow directory. The examples in this manual
page will use
.I /usr/local/stow
as the stow directory, so that individual
packages will be, for example,
.I /usr/local/stow/perl
and
.IR /usr/local/stow/emacs .
.PP
An ``installation image'' is the layout of files and directories
required by a package, relative to the target directory. Thus, the
installation image for Perl includes: a
.I bin
directory containing
.I perl
and
.I a2p
(among others); an
.I info
directory containing Texinfo
documentation; a
.I lib/perl
directory containing Perl libraries; and a
.I man/man1
directory containing man pages.
.PP
A ``package directory'' is the root of a tree containing the
installation image for a particular package. Each package directory
must reside in a stow directory--e.g., the package directory
.I /usr/local/stow/perl
must reside in the stow directory
.IR /usr/local/stow .
The ``name'' of a package is the name of its
directory within the stow directory--e.g.,
.IR perl .
.PP
Thus, the Perl executable might reside in
.IR /usr/local/stow/perl/bin/perl ,
where
.I /usr/local
is the target
directory,
.I /usr/local/stow
is the stow directory,
.I /usr/local/stow/perl
is the package directory, and
.I bin/perl
within
is part of the installation image.
.PP
A ``symlink'' is a symbolic link. A symlink can be ``relative'' or
``absolute''. An absolute symlink names a full path; that is, one
starting from
.IR / .
A relative symlink names a relative path; that is,
one not starting from
.IR / .
The target of a relative symlink is
computed starting from the symlink's own directory. Stow only creates
relative symlinks.
.SH OPTIONS
The stow directory is assumed to be the value of the 'STOW_DIR' environment 
variable or if unset the current directory, and the
target directory is assumed to be the parent of the current directory
(so it is typical to execute
.I stow
from the directory
.IR /usr/local/stow ).
Each
.I package
given on the command line is the name of a package in the stow
directory (e.g.,
.IR perl ).
By default, they are installed into the
target directory (but they can be deleted instead using `-D').
.TP
.I -n
.TP
.I --no
Do not perform any operations that modify the filesystem; merely
show what would happen. Since no actual operations are performed,
.I stow -n
could report conflicts when none would actually take
place (see ``Conflicts'' in the info manual);
but it won't fail to report conflicts
that
.B would
take place.
.TP
.I -c
.TP
.I --conflicts
Do not exit immediately when a conflict is encountered. This
option implies `-n', and is used to search for all conflicts that
might arise from an actual Stow operation. As with `-n', however,
false conflicts might be reported (see ``Conflicts'' in the info manual).
.TP
.I "-d DIR"
.TP
.I --dir=DIR
Set the stow directory to DIR instead of the current directory.
This also has the effect of making the default target directory be
the parent of DIR.
.TP
.I "-t DIR"
.TP
.I --target=DIR
Set the target directory to DIR instead of the parent of the stow
directory.
.TP
.I -v
.TP
.I --verbose[=N]
Send verbose output to standard error describing what Stow is
doing. Verbosity levels are 0, 1, 2, and 3; 0 is the default.
Using `-v' or `--verbose' increases the verbosity by one; using
`--verbose=N' sets it to N.
.TP
.I -D
.TP
.I --delete
Delete packages from the target directory rather than installing
them.
.TP
.I -R
.TP
.I --restow
Restow packages (first unstow, then stow again). This is useful
for pruning obsolete symlinks from the target tree after updating
the software in a package.
.TP
.I -V
.TP
.I --version
Show Stow version number, and exit.
.TP
.I -h
.TP
.I --help
Show Stow command syntax, and exit.
.SH "INSTALLING PACKAGES"
The default action of Stow is to install a package. This means
creating symlinks in the target tree that point into the package tree.
Stow attempts to do this with as few symlinks as possible; in other
words, if Stow can create a single symlink that points to an entire
subtree within the package tree, it will choose to do that rather than
create a directory in the target tree and populate it with symlinks.
.PP
For example, suppose that no packages have yet been installed in
.IR /usr/local ;
it's completely empty (except for the
.I stow
subdirectory, of course). Now suppose the Perl package is installed.
Recall that it includes the following directories in its installation
image:
.IR bin ;
.IR info ;
.IR lib/perl ;
.IR man/man1 .
Rather than creating
the directory
.I /usr/local/bin
and populating it with symlinks to
.I ../stow/perl/bin/perl
and
.I ../stow/perl/bin/a2p
(and so on), Stow
will create a single symlink,
.IR /usr/local/bin ,
which points to
.IR stow/perl/bin .
In this way, it still works to refer to
.I /usr/local/bin/perl
and
.IR /usr/local/bin/a2p ,
and fewer symlinks have
been created. This is called ``tree folding'', since an entire subtree
is ``folded'' into a single symlink.
.PP
To complete this example, Stow will also create the symlink
.I /usr/local/info
pointing to
.IR stow/perl/info ;
the symlink
.I /usr/local/lib
pointing to
.IR stow/perl/lib ;
and the symlink
.I /usr/local/man
pointing to
.IR stow/perl/man .
.PP
Now suppose that instead of installing the Perl package into an empty
target tree, the target tree is not empty to begin with. Instead, it
contains several files and directories installed under a different
system-administration philosophy. In particular,
.I /usr/local/bin
already exists and is a directory, as are
.I /usr/local/lib
and
.IR /usr/local/man/man1 .
In this case, Stow will descend into
.I /usr/local/bin
and create symlinks to
.I ../stow/perl/bin/perl
and
.I ../stow/perl/bin/a2p
(etc.), and it will descend into
.I /usr/local/lib
and create the tree-folding symlink
.I perl
pointing to
.IR ../stow/perl/lib/perl ,
and so on. As a rule, Stow only descends as
far as necessary into the target tree when it can create a tree-folding
symlink.
.PP
The time often comes when a tree-folding symlink has to be undone
because another package uses one or more of the folded subdirectories in
its installation image. This operation is called ``splitting open'' a
folded tree. It involves removing the original symlink from the target
tree, creating a true directory in its place, and then populating the
new directory with symlinks to the newly-installed package
.B and
to the
old package that used the old symlink. For example, suppose that after
installing Perl into an empty
.IR /usr/local ,
we wish to install Emacs.
Emacs's installation image includes a
.I bin
directory containing the
.I emacs
and
.I etags
executables, among others. Stow must make these
files appear to be installed in
.IR /usr/local/bin ,
but presently
.I /usr/local/bin
is a symlink to
.IR stow/perl/bin .
Stow therefore takes
the following steps: the symlink
.I /usr/local/bin
is deleted; the
directory
.I /usr/local/bin
is created; links are made from
.I /usr/local/bin
to
.I ../stow/emacs/bin/emacs
and
.IR ../stow/emacs/bin/etags ;
and links are made from
.I /usr/local/bin
to
.I ../stow/perl/bin/perl
and
.IR ../stow/perl/bin/a2p .
.PP
When splitting open a folded tree, Stow makes sure that the symlink
it is about to remove points inside a valid package in the current stow
directory.
.BR "Stow will never delete anything that it doesn't own" .
Stow ``owns'' everything living in the target tree that points into a
package in the stow directory. Anything Stow owns, it can recompute if
lost. Note that by this definition, Stow doesn't ``own'' anything
.B in
the stow directory or in any of the packages.
.PP
If Stow needs to create a directory or a symlink in the target tree
and it cannot because that name is already in use and is not owned by
Stow, then a conflict has arisen. See ``Conflicts'' in the info manual.
.SH "DELETING PACKAGES"
When the `-D' option is given, the action of Stow is to delete a
package from the target tree. Note that Stow will not delete anything
it doesn't ``own''. Deleting a package does
.B not
mean removing it from
the stow directory or discarding the package tree.
.PP
To delete a package, Stow recursively scans the target tree,
skipping over the stow directory (since that is usually a subdirectory
of the target tree) and any other stow directories it encounters (see
``Multiple stow directories'' in the info manual). Any symlink it finds that points into
the package being deleted is removed. Any directory that contained
only symlinks to the package being deleted is removed. Any directory
that, after removing symlinks and empty subdirectories, contains only
symlinks to a single other package, is considered to be a previously
``folded'' tree that was ``split open.'' Stow will re-fold the tree by
removing the symlinks to the surviving package, removing the directory,
then linking the directory back to the surviving package.
.SH "SEE ALSO"
The info manual ``Stow 1.3.3:
Managing the installation of software packages''
by Bob Glickstein, Zanshin Software, Inc.
.SH BUGS
Please report bugs in Stow using the Debian bug tracking system.
.PP
Currently known bugs include:
.IP *
The empty-directory problem. If package FOO includes an empty
directory--say, FOO/BAR--then:
.IP
1.
if no other package has a BAR subdirectory, everything's fine.
.IP
2.
if another stowed package, QUUX, has a BAR subdirectory, then
when stowing, TARGETDIR/BAR will be ``split open'' and the
contents of QUUX/BAR will be individually stowed. So far, so
good. But when unstowing QUUX, TARGETDIR/BAR will be
removed, even though FOO/BAR needs it to remain. A
workaround for this problem is to create a file in FOO/BAR as
a placeholder. If you name that file
.IR .placeholder ,
it will
be easy to find and remove such files when this bug is fixed.
.IP *
When using multiple stow directories (see ``Multiple stow
directories'' in the info manual), Stow fails to ``split open'' tree-folding symlinks
(see ``Installing packages'' in the info manual) that point into a stow directory
which is not the one in use by the current Stow command. Before
failing, it should search the target of the link to see whether
any element of the path contains a
.I .stow
file. If it finds one,
it can ``learn'' about the cooperating stow directory to
short-circuit the
.I .stow
search the next time it encounters a
tree-folding symlink.
.SH AUTHOR
This man page was constructed by Charles Briscoe-Smith from
parts of Stow's info manual. That manual contained the following
notice, which, as it says, applied to this manual page, too. The text
of the section entitled ``GNU General Public License'' can be found in
the file
.I /usr/share/common-licenses/GPL
on any Debian GNU/Linux system. If you don't have access to a Debian
system, or the GPL is not there, write to the Free Software Foundation,
Inc., 59 Temple Place, Suite 330, Boston, MA, 02111-1307, USA.
.IP
Software and documentation Copyright (C) 1993, 1994, 1995, 1996 by
Bob Glickstein <bobg+stow@zanshin.com>.
.IP
Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.
.IP
Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the section entitled ``GNU General Public License'' is included with
the modified manual, and provided that the entire resulting derived
work is distributed under the terms of a permission notice identical to
this one.
.IP
Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that this permission notice may be stated in a
translation approved by the Free Software Foundation.