xd - Online in the Cloud

PROGRAM:

NAME

xd - eXtra fast Directory changer

SYNOPSIS

xd [OPTIONS] arguments

DESCRIPTION

The program xd is used to perform eXtra fast Directory changes. Usually to change a
directory the user is required to enter a command like, e.g., cd /usr/local/bin, possibly
with the aid of shell completion. In many cases this is a tedious task: shell completion
shows all entries, including files, when we’re only interested in directories and the full
specification of our intented directory may eventually require many keyboard actions.

Xd was designed a long time ago (in the early 90s) to reduce the effort of changing a
directory. Often we’re well aware to which directory we want to change, and it’s easy to
produce the initial directory characters of that directory. E.g., if the intent is to cd
to /usr/local/bin, it’s rather easy to produce the letters ulb.

Xd capitalizes on this capability. By providing the initial directory characters of
directories xd will determine the proper expansion allowing you to change directories
fast. So, entering the command xd ulb will result in the expansion /usr/local/bin.

Often life is not that easy. Often there are multiple expansions from a given set of
initial characters. E.g., when entering xd ulb xd may find several alternatives. E.g.,

1: /usr/lib/base-config
2: /usr/lib/bonobo
3: /usr/lib/bonobo-activation
4: /usr/local/bin

If these are the alternatives, this is exactly what xd will show you. Then, by simply
pressing the 3 key (no Enter key required) xd will produce the required /usr/local/bin.

Commands to xd can be specified so as to fine-tune xd’s behavior:

o By default (as specified by the configuration file, see below) expansions may start
at the user’s home directory or at the system’s root directory.

o Initial character /: If the first character of the command is / all expansions will
be performed from the system’s root directory. E.g., xd /t will result in /tmp but
not in /home/user/tmp.

o Initial character .: If the first character of the command is . all expansions will
be performed from the user’s home directory. E.g., xd .t will result in
/home/user/tmp but not in /tmp

o Initial character 0: If the first character of the command is 0, all expansions
will start at the current working directory. In fact, this is a specialization of
the following, more general form:

o Initial character 1..9: If the first character of the command is a digit between 1
and 9 all expansions will start at that parent directory level of the current
working directory (up to the system’s root directory). E.g., if the current working
directory is /usr/share/doc then xd 2lb will offer the alterative /usr/local/bin:
two steps up, then look for directories starting with l and therein directories
starting with b.

o Separators (space, forward slash and underscore ( , / and _)): sometimes it is
clear that there are many alternatives and the intention is to reduce that number.
By using a separator subsequently nested directories must start with the characters
between the separators. E.g., xd u l bi will not produce the alternative
/usr/lib/base-config anymore, since base-config does not start with bi. In this
case only /usr/local/bin is produced. Separators may be mixed (xd u/l bi is
identical to xd u l bi). Since the / can also be used as a root-directory
specification, a conflict is implied by a command like xd /u l bi. This conflict is
solved by given the initial character a higher precedence than the separator. Using
the underscore (_) separator in this case is another way to solve the conflict
(which in practice hardly ever occurs).

If there’s only one solution, Xd will write that directory to its standard output stream.
If there are multiple solutions, a list of at most 62 alternatives (10 for the numbers
0..9, 26 for the letters a..z and 26 for the letters A..Z) will be written to the standard
error stream from which the user may select an alternative by simply pressing the key
associated with the selection of choice. If no selection is requested any other key may be
pressed (e.g., the space bar or the Enter key). If there is no solutioon xd will write the
text No Solutions to the standard error stream.

When xd is given at least one argument, all its output is sent to the standard error
stream, but for the selected directory name which is written to the standard output
stream. If no selection is made or if the selection process is aborted a single dot is
written to the standard output stream. Usually xd will be called by a shell alias,
providing the cd command with xd’s output (see below at the SHELL SCRIPTS section)
executing cd `xd $*`. The default dot produced by xd will then prevent a unintended change
of directory.

If xd is called without arguments then usage information is written to the standard error
stream.

Xd may be further configured using options and a configuration file, discussed in the
OPTIONS and CONFIGURATION FILE sections below.

GENERALIZED DIRECTORY SEARCH

Starting with version 3.10.0 xd also supports generalized directory search command
processing (GDS). When GDS is requested separators are no longer required, and xd will
find all possible alternatives resulting from all possible sequential combinations of the
initial search command. GDS is activated either by specifying the -g command line flag or
by entering generalized-search in xd’s configuration file. Alternatively, when the latter
is specified then the --traditional command line option will suppress GDS.

Under GDS each initial substring of the command to xd will be considered as the initial
characters of a directory. E.g., if the command xd tmps is entered using GDS then
directories matching the following search patterns will be found;

o /t*/m*/p*/s*/

o /t*/m*/ps*/

o /t*/mp*/s*/

o /t*/mps*/

o /tm*/p*/s*/

o /tm*/ps*/

o /tmp*/s*/

o /tmps*/ Only the first of these will be considered under the traditional processing
mode.

Multiple command line arguments, the slash and the underscore can still be used with GDS
in which case they force a directory change in the considered patterns. E.g., with the
command xd tm/ps the following patterns will be considered:

o /t*/m*/p*/s*/

o /t*/m*/ps*/

o /tm*/p*/s*/

o /tm*/ps*/ In this set all of the previous patterns showing the ...mp...
combination were dropped, as a directory change is forced between the m and p
characters.

RETURN VALUE

Xd returns 0 to the operating system unless an error occurs (e.g., when a non-existing
configuration file is specified), or xd’s version or usage info is shown or requested.

OPTIONS

If available, single letter options are listed between parentheses following their
associated long-option variants. Single letter options require arguments if their
associated long options require arguments as well.

o --add-root condition
If the search starts at the user’s home directory an additional search starting at
the system’s root directory may be performed as well, depending on the value
specified for the add-root option. Alternatives are never (no additional search is
performed); if-empty (an additional search is performed if the initial search did
not yield any directory); or always (an additional search is always performed).
There is also a configuration file directive add-root (see below).

o --all -a
If the configuration file (see below) contains ignore directives then these
directives are ignored when computing the alternatives from which the user may
select a directory to change to.

o --config-file=filename (-c)
The name of an xd configuration file. By default xd will look for the file .xdrc in
the user’s home directory. The existence of the default file is optional.

o --directories inclusion
Directories may be also be reached via symbolic links. The inclusion type all will
add these symbolic links to the list of alternatives. The inclusion type unique
will prevent the symbolic links from being added to the list of alternatives. There
is also a configuration file directive directives (see below).

o --generalized-search -g
When this option is specified xd will use GDS unless the directive traditional is
specified in the configuration file.

o --help (-h)
Basic usage information is written to the standard error stream.

o --history [filename]
A history of previously made choices is kept in the file filename. If --history is
specified, but the filename is left empty the history file $HOME/.xd.his is used.
This file should only be modified by xd itself. If you can’t resist editing it then
use the following example showing the format of the lines in the history file.

1292596154 1 /home/frank/svn/xd/

The first field is the time (in seconds since the epoch) the entry was written, the
second field is the number of times the entry has been selected and the third field
is the associated path.

o --history-lifetime spec
The lifetime of the entries in the history file. The specification consists of a
number followed by D, W, M or Y, representing, resp. days, weeks, months, or years.
A month is considered a period of 30 days, a year a period of 365 days. If the
specification is omitted a lifetime of 1M (one month) is used. Entries older than
history-lifetime are disregarded as history-items and are removed from the history
file.

o --history-maxsize nr
The maximum number of entries the history file may contain. By default there is no
limit. When history-maxsize is specified and more than the maximum number of
history items are found in the history file then the nr most popular choices are
kept. Usually the cut-off point will be somewhere within a popularity category. In
that case the most recently selected alternatives within that category are kept.

o --history-position [top|bottom]
When specified alternatives found in the history will be displayed either at the
top of the list or at the bottom of the list. If this option is omitted then the
elements in the history will be intermixed with new alternatives. The next option
history-separate is only used when this option is also specified. By merely
specifying history-position the history items are shown at the top of the list.

o --history-separate
When specified, a blank line is written between the items in the history and new
alternatives (not previously selected). This option is only interpreted when the
previous option is also specified.

o --icase -i
This option is used to specify case-insensitive pattern matching. E.g., specifying
xd /ub returns the directory /usr/bin, but not a directory like /UnSpecified/Books,
which is returned by xd /UB. However, xd -i /ub (using any letter casing for the
specification) returns both directories. The option icase could of course be
specified in the configuration file, which which case case-insensitive matching is
used by default. In the latter case specifying -i as a command line option reverts
the matching procedure to case-sensitive directory matching. In general, when an
even number of icase specifications is provided xd uses case-sensitive directory
matching, while an odd number of icase specifications results in case-insensitive
directory matching.

o --start-at origin
Defines the default start location of directory searches. Origin home results in
all default searches to start at the user’s home directory. Origin root results in
searches to begin at the disk’s root (/) directory. There is also a configuration
file directive start-at (see below).

o --traditional
When this option is specified xd will not use GDS but will use its traditional
mode. It overrules a generalized-search directive specified in the configuration
file as well as the -g option.

o --verbose (-V)
More extensive information about the actions taken by the xd program is written to
the standard error stream.

o --version (-v)
Xd’s version number is written to the standard error stream.

CONFGURATION FILE

The default configuration file is .xdrc in the user’s home directory. It may be overruled
by the program’s --config-file option.

Empty lines are ignored. Information at and beyond #-characters is interpreted as comment
and is ignored as well.

All directives in xd configuration files follow the pattern

directive value

but for some directives value is optional.

A line may at most contain one directive, but white space (including comment at the end of
the line) is OK. The same directive may be specified multiple times, in which case the
last directive will be used (with the exception of the ignore directive, see below). All
directives are interpreted case sensitively. Non-empty lines not beginning with a
recognized directive are silently ignored.

The following directives can be used in the configuration file. Default values are shown
between parentheses.

o add-root when (if-empty)
If the search starts at the user’s home directory an additional search starting at
the system’s root directory may be performed as well, depending on the value
specified for the add-root directive.
If when is specified as always then an additional search is always performed.
If it is specified as if-empty then an additional search is performed if the
initial search (starting at the user’s home directory) did not yield any directory.
If it is specified as never no additional search is performed.
This directive is overruled by the ---add-root command line option.

o directories which (all)
Directories may be also be reached via symbolic links. The specification all will
add these symbolic links to the list of alternatives. The specification unique will
prevent the symbolic links from being added to the list of alternatives.
This directive is overruled by the ---directories command line option.

o generalized-search
When this directive is specified xd will use GDS by default.

o history [filename]
A history of previously made choices is kept in the file filename. If history is
specified, but the filename is left empty the history file $HOME/.xd.his is used.
This file should only be modified by xd itself. If you can’t resist editing it then
use the following example showing the format of the lines in the history file.

1292596154 1 /home/frank/svn/xd/

The first field is the time (in seconds since the epoch) the entry was written, the
second field is the number of times the entry has been selected and the third field
is the associated path.

o history-lifetime spec
The lifetime of the entries in the history file. The specification consists of a
number followed by D, W, M or Y, representing, resp. days, weeks, months, or years.
A month is considered a period of 30 days, a year a period of 365 days. If the
specification is omitted a lifetime of 1M (one month) is used. Entries older than
history-lifetime are disregarded as history-items and are removed from the history
file.

o history-maxsize nr
The maximum number of entries the history file may contain. By default there is no
limit. When history-maxsize is specified and more than the maximum number of
history items are found in the history file then the nr latest choices are kept.
Each previously made selection counts as one. If a new alternative is selected it
always becomes an element in the history list.

o history-position [top|bottom]
When specified alternatives found in the history will be displayed either at the
top of the list or at the bottom of the list. If this option is omitted then the
elements in the history will be intermixed with new alternatives. The next
directive history-separate is only used when this directive is also specified. By
merely specifying history-position the history items are shown at the top of the
list.

o history-separate
When specified, a blank line is written between the items in the history and new
alternatives (not previously selected). This directive is only interpreted when the
previous directive is also specified.

o --icase -i
This specification is used to request case-insensitive pattern matching. If this
option is entered in the configuration file then specifying xd /ub returns the
directory /usr/bin as welll as a directory like (assuming it exists)
/UnSpecified/Books. When specified in the configuration file, the command-line
option -i reverts the matching procedure back to case-sensitive directory matching.
In general, when an even number of icase specifications is provided xd uses
case-sensitive directory matching, while an odd number of icase specifications
results in case-insensitive directory matching.

o ignore path
The configuration file may contain multiple ignore directives which are --different
from the way other directives are handled-- all interpreted. Each ignore directive
is followed by a path specification as shown in a list of alternatives produced by
xd or an initial substring of such a path terminating in a * character. When xd
encounters a path matching any of the ignore directives (with the * interpreted as
`any further directory name’ specification) it will not display that path in its
list of alternatives. This directive is overruled by the ---all command line
option.

o start-at value (home)
Defines the default start location of directory searches. Values are home and root.
When home is specified all searches start at the user’s home directory. When root
is specified searches start at the disk’s root (/) directory. If the directory is
omitted or if another value is specified then the default is used, which is home.
This directive is overruled by the ---start-at command line option.

o traditional
This directive may be used to request the use of xd’s traditional mode. It
overrules the -g command line option and the generalized-search directive. )

SHELL SCRIPTS

Assuming xd is installed in /usr/bin scripts can be defined around xd for various shell
programs. This allows the shell to change directories under control of xd.

To use xd with the bash(1)-shell, the following function can be used (which could be added
to, e.g., .bash_login):

xd() # function to do `cd` using `xd`
{
cd `/usr/bin/xd $*`
}

To use xd with the tcsh(1)-shell, the following alias can be added to, e.g., the ~/.alias
file:

alias xd ’cd `\xd \!*`’

Having defined the xd alias or script xd ... commands will result in the automatic or
selected change of the current working directory

EXAMPLES

xd ulb - all directories starting subsequently,
with u, l and b origin is default, or
specified in .xdrc as home or root

xd 0t - all directories starting with t below the cwd

xd 2t - all directories starting at the `grandparent’
(2 steps up) of the cwd

xd --start-at root t
- all directories at the root starting with t

xd .. - all directories starting with a dot in the cwd

Assuming the following directories exist:

/usr/lib/bonobo
/usr/lib/bonobo-activation
/usr/local/bin

then the following two ignore specifications in xd’s configuration file will result in
ignoring the bonobo directory alternatives:

First specification:

ignore /usr/lib/bonobo
ignore /usr/lib/bonobo-activation

Second specification:

ignore /usr/lib/bonobo*

Use xd online using onworks.net services