bash-completion/README

$Id: README,v 1.16 2002/12/05 05:26:28 ianmacd Exp $


INSTALLATION
------------

If you are installing the source file manually as opposed to using a packaging
system such as dpkg or rpm, put it somewhere on your system and source it from
either /etc/bashrc or ~/.bashrc.

Here's one possible way of doing that from /etc/bashrc:

bash=${BASH_VERSION%.*}; bmajor=${bash%.*}; bminor=${bash#*.}
if [ "$PS1" ] && [ $bmajor -eq 2 ] && [ $bminor '>' 04 ] \
   && [ -f /etc/bash_completion ]; then # interactive shell
        # Source completion code
        . /etc/bash_completion
fi
unset bash bmajor bminor

This code checks that the version of bash that is parsing the code is later
than 2.04 and, if so, sources the bash completion code.

While this code may, at first, seem overly complex, the advantage of using it
is that it will also parse correctly when interpreted by bash 1.x. If you have
bash 1.x and bash 2.x users on your system, you must avoid using constructs
that were not valid under 1.x syntax.

If you are putting the bash completion source file somewhere other than
/etc/bash_completion, you should ensure that $BASH_COMPLETION is set to point
to it before you source it. Your ~/.bashrc file is a good place to do this.


TROUBLESHOOTING
---------------

If you get errors about 'complete' or 'compgen' not accepting the -g flag,
you are probably running bash 2.05 and should either apply the group completion
patch, download a prepatched bash binary of 2.05, or upgrade to 2.05a or later.

If you find that some commands, such as 'cd /usr<Tab>', end with a trailing
space instead of appending a /, you are probably running the base version of
bash 2.05, which suffers from a bug that causes the '-o filenames' option to
the complete built-in to be ignored. You can fix this by applying the following
the following official patch from the bash maintainer:

	ftp://ftp.cwru.edu/pub/bash/bash-2.05-patches/bash205-006

If you get errors about 'complete' not accepting the -o flag, you are probably
running bash 2.04. In this case, you should upgrade to bash 2.05a or later.
However, I have endeavoured to make the code detect this version of bash and
work around this issue, so please inform me if you still encounter this error.

Copies of the patches and prepatched versions of bash are available from:

			http://www.caliban.org/bash/

If you find that a given function is producing errors under certain
circumstances when you attempt completion, try running 'set -v' or 'set -x'
prior to attempting the completion again. This will produce useful debugging
output that will aid me in fixing the problem if you are unable to do so
yourself. Turn off the trace output by running either 'set +v' or 'set +x'.


KNOWN PROBLEMS
--------------

I.

There seems to be some issue with using the bash built-in cd within Makefiles.
When invoked as /bin/sh within Makefiles, bash seems to have a problem changing
directory via the cd command. A work-around for this is to define
SHELL=/bin/bash within your Makefile. This is believed to be a bug in bash.

II.

The have() function is used to conserve memory by only installing completion
functions for those programs that are actually present on your system. The
current method of determining whether or not a given binary is present is
whether or not it is in your $PATH.

This approach has the disadvantage that sudo completion will not be able to
perform sub-completion on, say, service, if /sbin is not in your path, which,
as an unprivileged user, it typically isn't.

The work-around for this is to put all directories of binaries for which you
require completion into your $PATH variable prior to sourcing bash_completion.

III.

Many of the completion functions assume GNU versions of the various text
utilities that they call (e.g. grep, sed and awk). Your mileage may vary.


FAQ
---

Q. How can I insert my own local completions without having to reinsert them
   every time you issue a new release?

A. Put them in ~/.bash_completion, which is parsed at the end of the main
   completion script.

Q. I author/maintain package X and would like to maintain my own completion
   code for this package. Where should I put it to be sure that interactive
   bash shells will find it and source it?

   Put it in the directory pointed to by $BASH_COMPLETION_DIR, which is defined
   at the beginning of the main completion script. Any scripts placed in this
   directory will be sourced by interactive bash shells.

Q. I use CVS in combination with passwordless ssh access to my remote
   repository. How can I have the cvs command complete on remotely checked-out
   files where relevant?

A. Define $COMP_CVS_REMOTE. Setting this to anything will result in the
   behaviour you would like.

Q. When I'm running a ./configure script and completion returns a list of
   long options to me, some of these take a parameter,
   e.g. --this-option=DESCRIPTION.

   Running ./configure --help lists these descriptions, but everything after
   the '=' is stripped when returning completions, so I don't know what kind
   of data is expected as a given option's parameter.

   Is there a way of getting ./configure completion to return the entire
   option string, so that I can see what kind of data is required and then
   simply delete the descriptive text and add my own data?

A. Define $COMP_CONFIGURE_HINTS. Setting this to anything will result in the
   behaviour you would like.

Q. When doing tar completion on a file within a tar file like this:

   tar tzvf foo.tar.gz <Tab>

   the pathnames contained in the tar file are not displayed correctly. The
   slashes are removed and everything looks like it's in a single directory.
   Why is this?

A. It's a choice I had to make. bash's programmable completion is limited in
   how it handles the list of possible completions it returns.

   Because the paths returned from within the tar file are likely not existing
   paths on the file system, '-o dirnames' must be passed to the complete
   built-in to make it treat them as such. However, then bash will append a
   space when completing on directories during pathname completion to the tar
   files themselves.

   It's more important to have proper completion of paths to tar files than
   it is to have completion for their contents, so this sacrifice was made
   and '-o filenames' is used with complete instead.

   If you would rather have correct path completion for tar file contents,
   define $COMP_TAR_INTERNAL_PATHS *before* sourcing bash_completion.

Q. When completing on a symlink to a directory, bash does not append the
   trailing / and I have to hit <Tab> again. I don't like this.

A. This has nothing to do with bash_completion. It's the default for
   completing symlinks to directories in bash 2.05a, and was added because
   sometimes you want to operate on the symlink itself, rather than what it
   points to.

   In bash 2.05b and later, you can get the pre-2.05a behaviour back by
   putting 'set mark-symlinked-directories on' in your /etc/inputrc or
   ~/.inputrc file.

Q. This code is rubbish/not bad/pretty good/the best thing since sliced bread.
   How can I show my appreciation?

A. If you're a registered Freshmeat user, take a moment to rate the project at:

	http://freshmeat.net/rate/19041/

   Of course, writing to me and letting me know how you feel also works.
   Patches and new completion routines are most welcome, too.

Q. How can I stay abreast of new releases?

A. If you're a registered Freshmeat user, you can subscribe to new release
   announcements at:

	http://freshmeat.net/subscribe/19041/


CONTRIBUTING
------------

Contributions to the bash completion project are more than
welcome. Fixes, clean-ups and improvements of existing code are much
appreciated, as are completion functions for new commands.

If you wish to contribute code, please bare the following coding
guidelines in mind:

- Do not use Perl, Ruby, Python etc. to do text processing unless the
  command for which you are writing the completion code implies the
  presence of one of those languages.

  For example, if you were writing completion code for perldoc(1), the
  use of Perl to achieve your goal would be acceptable. irb(1)
  completion would make the use of Ruby acceptable.

  Even so, please consider alternatives to these large and slow to
  start interpreters. Use lightweight programs such as grep(1), awk(1)
  and sed(1).

- Use the full power of bash 2.x. Programmable completion has only
  been available since bash 2.04, so you may as well use all the
  features of that version of bash to optimise your code. However, be
  careful when using features added since 2.04, since not everyone
  will be able to use them.

  For example, here strings (<<<) were not added until 2.05b, so don't
  use them for the time being. On the other hand, extended globs often
  enable you to avoid the use of external programs, which are
  expensive to fork and execute, so do use those:

  ?(pattern-list) - match zero or one occurences of patterns
  *(pattern-list) - match zero or more occurences of patterns
  +(pattern-list) - match one or more occurences of patterns
  @(pattern-list) - match exactly one of the given patterns
  !(pattern-list) - match anything except one of the given patterns

- Following on from the last point, try to save external processes
  whenever you can. Completion functions need to be fast, so
  sacrificing some code legibility for speed is acceptable.

  For example, judicious use of sed(1) can save you from having to
  call grep(1) and pipe the output to cut, which saves a fork(2) and
  exec(3).

  Sometimes you don't even need sed(1) or other external programs at
  all, though. Use of constructs such as ${parameter#word},
  ${parameter%word} and ${parameter/pattern/string} can provide you a
  lot of power without having to leave the shell.

  For example, if $foo contains the path to an executable, ${foo##*/}
  will give you the basename of the program, without having to call
  basename(1). Similarly, ${foo%/*} will give you the dirname, without
  having to call dirname(1).

  As another example,

    bar=$( echo $foo | sed -e 's/bar/baz/g' )

  can be replaced by:

    bar=${foo//bar/baz}

  These forms of parameter substitutions can also be used on arrays,
  which makes them very powerful.

- Do not write to the file-system under any circumstances. This can
  create race conditions, is inefficient, violates the principle of
  least surprise and lacks robustness.

- Send your patches as unified diffs. You can make this with 'diff -u'.

- Send small, incremental diffs that affect a single function. Don't
  cram massive, unrelated patches into a single diff.

- If your code was written for a particular platform, try to make it
  portable to other platforms, so that everyone may enjoy it. If your
  code works only with the version of a binary on a particular
  platform, ensure that it will not be loaded on other platforms that
  have a command with the same name.

  In particular, do not use GNU extensions to commands like sed and
  awk if you have the choice. If you really must use them, however, do
  feel free to do so.

- Read the existing source code for examples of how to solve
  particular problems. Read the bash man page for details of all the
  programming tools available to you within the shell.

- Please test your code thoroughly before sending it to me. I don't
  have access to all the commands for which I am sent completion
  functions, so I am unable to test them personally. If your code is
  accepted into the distribution, a lot of people will try it out, so
  try to do a thorough job of eradicating all the bugs before you send
  it to me.
  
-- 
Ian Macdonald <ian@caliban.org>