################################################################################
# #
# smartcd - make your shell come alive #
# #
################################################################################
WHAT IS SMARTCD?
smartcd is a library for bash and zsh which brings transformative power
to your fingertips.
The basic premise is that as you move around your computer using the shell,
actions can be automatically taken to provide you with the environment you
really want, not the one you're accustomed to putting up with.
Have you ever...
* Created a file for a project to alter your environment by setting
variables or creating aliases so that things work correctly, one which
you need to remember to load by hand
* Struggled to set up your shell's configuation to support conflicting
needs for different uses
* Wished that your prompt could be made to say something or be a different
color when you are in a sensitive directory
* Wanted a daemon process to run automatically when you go to work on a
project, and shut down when you finish
* Update your project from source control when you enter
* Attach to a particular screen(1) session when working on something
These are just a few examples of problems people are solving with smartcd.
OK, HOW DO I USE IT?
It's stupid easy. If you have already downloaded the archive or checked out
the source, you can:
make install
source ~/.smartcd/lib/core/smartcd
smartcd config
However, if you would rather skip all that and simply have it install iself,
try this:
curl -L http://smartcd.org/install | bash
Either method will prompt you to configure a small number of settings, and
then help you set up your shell to load it on login.
Once it is installed, you're ready to go. All actions are available through
the `smartcd` command.
Usage: smartcd ( edit | show | filename | template | setup | config ) [args]
If you run `smartcd edit enter`, it will launch your editor to allow you to
begin creating a script for the current directory which will run when you
enter. Its counterpart, `smartcd edit leave`, will create a script that runs
when you cd away from the current directory.
An auxiliary library is provided with smartcd called varstash. This provides
you with a powerful mechanism which saves the definitions of variables,
aliases, and shell functions to allow you to change or unset them temporarily.
Once you are finished, it will allow you to (or automatically) restore their
prior values.
For example,
autostash PATH=/path/to/my/project/bin:$PATH
autostash alias restart="apachectl restart"
restart
will save the value of your $PATH, and prepend a project-specific directory
to it. smartcd will automagically restore its old value when you leave the
directory.
The second line creates a temporary alias which is probably something only
meaningful to the directory you are in, allowing you to keep concise aliases
that won't get in your way, and allow you to re-use them between projects.
And these commands are immediately available, as shown by the third line,
which makes use of the newly defined alias to restart your server.
You could instead create the files non-interactively
echo 'autostash PATH=__PATH__/temporary/path:$PATH' | smartcd edit enter
which also highlights a convenient feature that replaces __PATH__ with the
directory name before the script is run.
If you like doing things by hand, you may prefer
mkdir -p ~/.smartcd/scripts/some/directory
echo 'autostash PATH=__PATH__/temporary/path:$PATH' >> ~/.smartcd/scripts/some/directory/bash_enter
HOW DOES IT WORK?
Scripts for smartcd are contained in a directory structure under your home,
in the .smartcd directory. As you change directory, it will look for files
which correspond to where you are leaving from and going to, and run them for
you.
The primary way of doing this is to create a "cd" function which calls
`smartcd cd`. This also works with push and popd. The simplest way to
create these wrappers is to call `smartcd setup cd`, `smartcd setup pushd`,
and `smartcd setup pushd`. When you `smartcd config`, this will be set up
for you.
If you prefer (or in addition), you can hook the prompt command.
This sets PROMPT_COMMAND in bash, or precmd in zsh. This is enabled using
`smartcd setup prompt-hook`. After calling smartcd, it will call any prior
command for those hooks. This feature allows users with the "autocd" option
set in their shell to also benefit from smartcd.
The structure of .smartcd will mirror the filesystem hierarchy you wish to
configure. For example:
Path Action Script
------------------------------------------------------------
/foo/bar enter ~/.smartcd/scripts/foo/bar/bash_enter
/foo/bar/baz leave ~/.smartcd/scripts/foo/bar/baz/bash_leave
You can edit and read these files with the smartcd command using the
"edit", "show", and "filename" actions.
user@host:/usr/local/bin$ smartcd filename enter
/home/user/.smartcd/scripts/usr/local/bin/bash_enter
user@host:/usr/local/bin$ smartcd show leave
/home/user/.smartcd/scripts/usr/local/bin/bash_leave does not exist
user@host:/usr/local/bin$ smartcd show enter
/home/user/.smartcd/scripts/usr/local/bin/bash_enter exists
-------------------------------------------------------------------------
echo "testing"
-------------------------------------------------------------------------
user@host:/usr/local/bin$ smartcd edit enter
--> edits ~/.smartcd/scripts/usr/local/bin/bash_enter
user@host:/usr/local/bin$ echo "some-command" | smartcd edit enter
One thing to note is that going from a directory to its child is not
considered "leaving", so the bash_leave will not be run until you go to
another directory that doesn't contain that same directory as part of
its path. The scripts are run as appropriate if they exist for each
level going back to the common element between the paths.
If you cd from /foo/bar/baz to /foo/quux/biff, the following actions would
take place:
1) bash_leave for /foo/bar/baz
2) bash_leave for /foo/bar
3) bash_enter for /foo/quux
4) bash_enter for /foo/quux/biff
These scripts are run in the interactive shell using eval, so any variables
or other environment effects will take place in the user's shell directly.
WHAT ARE SOME COMMON RECIPES?
Here are some examples of useful setups that have been created so far
PROMPT
If you want a visual cue that you need to be careful, it might make sense
to change your prompt. Here's one that will temporarily make your prompt
red while leaving its actual value alone.
autostash PS1='\[\e[1;31m\]'"$PS1"'\[\e[0m\]'
Note the double-quotes around $PS1. This is not superfluous, if your
current value has any space characters in it, it's important to use quoting
because otherwise it would be seen as a second argument to autostash
SCREEN
This one can be a bit tricky since screen commands from within screen tend
to confuse it. And of course, creating a new screen window will execute
your bash_enter scripts.
So what we'll do is set a variable in the attaching shell which is seen
from within screen to prevent it from doing so.
if [[ -z $MYSCREEN ]]; then
autostash MYSCREEN=1
screen -c __PATH__/.screenrc -RRD my-special-screen-session
fi
PERLBREW
perlbrew is a system for installing multiple builds and versions of the Perl
language, allowing you to easily switch between them. This is very valuable
for development, but probably not what you want for your whole system.
Here is a recipe I've used to allow perlbrew to do its thing from within
a project folder
autostash PATH PERLBREW_PERL PERLBREW_VERSION PERLBREW_PATH PERLBREW_ROOT PATH_WITHOUT_PERLBREW
source /path/to/perlbrew/install/etc/bashrc
perlbrew is available at http://search.cpan.org/~gugod/App-perlbrew/
STOP/START
If you want something to start running when you enter the directory, and
stop running when you leave, you can certainly use smartcd for this. Here's
an example of how someone is using smartcd to start and stop a Plack service
### enter script ###
# temporarily define the functions stop and start
autostash stop start pidfile="__PATH__/.pid"
start() {
if [[ ! -f "$pidfile" ]] || ! kill -0 $(cat "$pidfile") >/dev/null 2>&1; then
(
builtin cd __PATH__/html
plackup &> /dev/null &
local pid=$!
echo $pid > "$pidfile"
echo "Started Plack with pid $pid"
)
fi
}
stop() {
if [[ -f "$pidfile" ]] && kill -0 $(cat "$pidfile") >/dev/null 2>&1; then
kill $(cat "$pidfile")
rm "$pidfile"
fi
}
# There are several things to make a note of here
#
# 1) The sub-shell created in the start() function is not actually necessary
# if `start` is _only_ run from within smartcd, since the extra `cd` command
# will not prevent you from ending up in the right directory. However, since
# this function can be called manually, it's safer to do this in a subshell.
#
# 2) I used `builtin cd` instead of just `cd` in start() to avoid smartcd being
# called during another call, possibly causing surprising results. However,
# if you actually want smartcd to be run in that situation, it's ok to do so.
#
# 3) Use __PATH__ liberally to ensure that files and actions are taken in the
# correct place, even after you've changed to a subdirectory of where the script
# was defined.
# Create an alias that calls both functions
autostash alias restart="stop; sleep 2; start"
# And automatically start-up on enter
start
### leave script ###
# Shut down when leaving. Yes, this function is still available here, and
# it will be removed by autounstash after this leave is complete
stop
and of course, if you want to be sure that this daemon is shut down properly
if you simply log out or close your shell, you will want the exit hook as well
# in your .smartcd_config, see `smartcd config`
smartcd setup exit-hook
WHAT ELSE CAN IT DO?
TEMPLATES
In addition to configuring scripts individually, smartcd supports a template
system, which can be set up to re-use common configuration among many
directories. This is controlled with the "smartcd template" action.
To create a new template based on the current directory, run:
smartcd template create some_template_name
This will create a new template named "some_template_name", and prepopulate
it from the bash_enter and bash_leave files corresponding to the working
directory, replacing any instance of your working directory with __PATH__.
You can then edit the contents with `smartcd template edit some_template_name`.
The `create` step is optional, and if you `edit` a template that is not yet
created you will start with an empty one.
Now that your template is ready, you'll want to use it somewhere. For this,
there are two options:
1) Run it "in-place", and all changes to the template will be dynamically
picked up by the enter and exit scripts which execute it
echo 'smartcd template run some_template_name' | smartcd edit enter
The `run` action will determine if you are in an "enter" or "leave" script,
and execute the correct portion of the template. This does not need to be
the only line in your script, and in fact you can even run more than one
template from the same script.
2) Copy the current contents of the template to the scripts for a directory,
as a one-time operation. This will not automatically propagate changes to
the places it is in use, and can be used as a way to quickly bootstrap
scripts but allow them to exist independently.
smartcd template install some_template_name
The other template editor actions are "show", "list", and "delete".
EXIT HOOK
By default, your enter scripts will be run when a shell is started. However,
the opposite is not the case. If you'd like your leave scripts to run when
the shell exits, smartcd is able to utilize the shell's EXIT trap hook to do
so, or in zsh, the zshexit hook. This is enabled by running
smartcd setup exit-hook
BACKUP
If you would like to back up your scripts and templates, or copy them to
another computer, you can use the provided export/import feature.
# Export your scripts
smartcd export > my_smartcd_backup
# Several methods to import them
smartcd import my_smartcd_backup
cat my_smartcd_backup | smartcd import
For more complete documentation, see the documentation in lib/core/smartcd.
OTHER LIBRARIES
VARSTASH
As already discussed, the included library lib/core/varstash provides several
functions for saving values to a temporary location so that you can edit
them, and then later restore the original value.
In addition to autostash, you could manually stash and unstash using
functions with those names if there is some need to do so
echo 'stash FOO=bar' | smartcd edit enter
echo 'unstash FOO' | smartcd edit leave
You may also trigger autostash's restore mechanism by calling
autounstash
by hand. It's safe to do so multiple times and it won't harm smartcd
if you do this.
If you run stash, unstash, or autostash interactively, they will instruct
you on how to create files for smartcd to run those commands for you. If
you do not wish to see this advice, set VARSTASH_QUIET=1. The library can
automatically follow its own advice and configure these files if you set
VARSTASH_AUTOCONFIG=1. It can do so, but also give you an opportunity to
make additional edits to the relevant file, if you set VARSTASH_AUTOEDIT=1.
Alias stashing was briefly mentioned, and it is supported to do in-line
stashing and declaration of an alias with autostash
autostash alias mycmd="do something crazy"
However, stashing functions looks like this:
autostash my_func
my_func() {
some_new_definition
}
It's useful to autostash something even before it's set, because that
triggers the mechanism which will unset them upon leaving. Since functions
cannot be declared inline with autostash, this is how you should do it.
ARRAYS
Bash added array support in version 2.0, but it doesn't have a very good
set of supporting built-ins. In particular, I find myself missing the Perl
functions push, pop, shift, unshift, reverse.
To provide these capabilities, another library, lib/core/arrays, is
included. The provided functions are:
apush - Add an element to the end of your array
apop - Remove the last element from the array and print it
ashift - Remove the first element from the array and print it
aunshift - Add an element to the beginning of the array
areverse - Reverse the order of elements in the array
afirst - Like ashift, but doesn't remove anything.
alast - Like apop, but doesn't remove anything.
anth - Retreive the n-th element of an array.
alen - Print the current number of elements in the array
acopy - Copy an array into a new variable
See documentation included in lib/core/arrays for more detail.
LICENSE
This code is Copyright (c) 2009,2012 Dave Olszewski <cxreg@pobox.com>
You may distribute under the terms of either the GNU General Public
License v2 or the Artistic License.
SEE ALSO
As with most ideas worth doing, there are other implementations of some
of the things provided by smartcd. Here are a few of them, and how they
differ from this library.
ondir - http://swapoff.org/ondir.html
* Written in C, and is executed by a "cd" function
* Requires manual and explicit variable setting and unsetting
direnv - https://github.com/zimbatm/direnv/
* Requires ruby
* Works only with PROMPT_COMMAND or precmd
* Does not walk directory hierarchy
* Does not support functions or aliases
* Is entirely "snapshot" based
* Runs files directly out of local directory, similar to "legacy mode"
EnvWatcher - https://github.com/MrMasterplan/EnvWatcher
* Requires python
* Only supports bash
* Is triggered manually, not automatically
* Does not walk directory hierarchy
* Is entirely "snapshot" based
* Does not allow other actions besides environment variable switching