1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
|
<html>
<head>
<link href="../lg.css" rel="stylesheet" type="text/css" media="screen, projection" />
<title>Using DCOP from the command line LG #97</title>
<style type="text/css" media="screen, projection">
<!--
.articlecontent {
position:absolute;
top:143px;
}
-->
</style>
</head>
<body>
<img src="../gx/2003/newlogo-blank-200-gold2.jpg" id="logo" alt="Linux Gazette"/>
<p id="fun">...making Linux just a little more fun!</p>
<div class="content articlecontent">
<div id="previousnexttop">
<A HREF="oregan.html" ><-- prev</A> | <A HREF="pramode.html" >next --></A>
</div>
<h1>Using DCOP from the command line</h1>
<p id="by"><b>By <A HREF="../authors/oregan.html">Jimmy O'Regan</A></b></p>
<p>
<h2>Introduction</h2>
<p>DCOP is KDE's IPC/RPC mechanism. If you understood that sentence, please feel free to skip the next paragraph.</p>
<p>DCOP stands for Desktop COmmunications Protocol, IPC stands for Inter-Process Communication; RPC stands for Remote
Procedure Call. In essence, they are means by which two programs can communicate, whether on the same machine or across
a network. In this regard, DCOP is similar to Microsoft's OLE Automation: it provides a simple way for developers to
provide access to the functions available in an application.</p>
<p>KDE was originally attempting to build a CORBA-based component system (the GNOME project originally started as this
project, but became a desktop project in a disagreement over the license the Qt widget set was using), but it was decided
that CORBA was too complicated, and two simpler systems were introduced; KParts, for embedded components; and DCOP.</p>
<p>A DCOP enabled application registers at launch time with the DCOP daemon, and registers its functions. When queried,
the dcop daemon provides a list of running processes and the functions they provide. This enables a range of applications,
such as the DCOP browser, or the DCOP to XMLRPC daemon; but the one I'm going to look at is 'dcop', which allows shell
access to DCOP.</p>
<p>Unlike other systems, such as GNOME's Bonobo or Microsoft's Automation, DCOP does not provide an activation system;
only running processes are listed by DCOP. Activating the application is left up to the user.</p>
<p>This article is about using DCOP to control KDE applications from the command line; links are provided at the end of the
page to developer information for those who wish to delve deeper into this technology.</p>
<h2>Using DCOP from the command line</h2>
<p>The 'dcop' program provides command line access to the DCOP system. The syntax is:</p>
<pre>dcop [application] [object] [function] [arguments ...]</pre>
<p>To see which applications are available, enter 'dcop' with no arguments</p>
<pre>
$ dcop
khelpcenter
kwin
kicker
kword-4354
kded
knotify
kio_uiserver
kalarmd
kcookiejar
konsole-4300
korgac
klauncher
kdesktop
klipper
ksmserver
</pre>
<p>Let's have a look at klipper, the KDE clipboard service:</p>
<pre>
$ dcop klipper
qt
klipper
</pre>
<p>We can assume that klipper is the object we're looking for here; the default object (i.e., the one you want, to control
the application) is normally given the same name as the application, with or without "IFace" appended, or is marked as
"default":</p>
<pre>
$dcop klipper klipper
QCStringList interfaces()
QCStringList functions()
QString getClipboardContents()
void setClipboardContents(QString s)
void clearClipboardContents()
int newInstance()
void quitProcess()
</pre>
<p>Now, I think the most interesting functions here are setClipboardContents and getClipboardContents. In fact, I've been
using setClipboardContents in a konsole window to add the shell output above:</p>
<pre>dcop klipper klipper setClipboardContents "$(dcop klipper klipper)"</pre>
<p>Now, to be honest, this isn't the best example, as it's a lot quicker to use the mouse than to type that, but it can
become a lot more useful if set as an alias, e.g.</p>
<pre>alias klip="dcop klipper klipper setClipboardContents"</pre>
<p>I've always thought it would be useful to have post-it notes available from the shell - DCOP makes that possible.</p>
<pre>
$dcop knotes KNotesIface
QCStringList interfaces()
QCStringList functions()
int newNote(QString name,QString text)
int newNoteFromClipboard(QString name)
ASYNC showNote(int noteId)
ASYNC hideNote(int noteId)
ASYNC killNote(int noteId)
QMap<int,QString> notes()
ASYNC setName(int noteId,QString newName)
ASYNC setText(int noteId,QString newText)
QString text(int noteId)
ASYNC sync(QString app)
bool isNew(QString app,int noteId)
bool isModified(QString app,int noteId)
</pre>
<p>So let's add a note:</p>
<pre>dcop knotes KNotesIface newNote "A note" "Stuff I want to keep track of"</pre>
<p>Sure enough, a bright yellow note pops up. </p>
<p>Let's see what notes are available:</p>
<pre>
$dcop knotes KNotesIface notes
1->A note
</pre>
<p>After adding a few more nonsense notes, maybe I want to have them in a text file, so I wrote a silly script to go
with a silly idea:</p>
<pre>
#!/bin/bash
n=$(dcop knotes KNotesIface notes|awk -F- '{print $1}'|tail -1)
dcop knotes KNotesIface notes > $1
echo >> $1
for ((i=1;i<=$n;i++));do echo -n "$i: "; dcop knotes KNotesIface text $i;echo;done >> $1
</pre>
<h2>Summary</h2>
<p>DCOP is a powerful means to control KDE applications. As more and more developers recognise its usefulness, we get
closer to a nice blend of desktop eye candy and scriptability.</p>
<h2>Links</h2>
<ul>
<li><a href="http://developer.kde.org/documentation/library/kdeqt/dcop.html">Programming with DCOP</a>
<li><a href="http://developer.kde.org/documentation/books/kde-2.0-development/ch13.html">Chapter from KDE 2.0 Development</a>
</ul>
</p>
<!-- *** BEGIN author bio *** -->
<P>
<P>
<!-- *** BEGIN bio *** -->
<P>
<img ALIGN="LEFT" ALT="[BIO]" SRC="../gx/2002/note.png">
<em>
</em>
<br CLEAR="all">
<!-- *** END bio *** -->
<!-- *** END author bio *** -->
<div id="articlefooter">
<p>
Copyright © 2003, Jimmy O'Regan. Copying license
<a href="http://linuxgazette.net/copying.html">http://linuxgazette.net/copying.html</a>
</p>
<p>
Published in Issue 97 of Linux Gazette, December 2003
</p>
</div>
<div id="previousnextbottom">
<A HREF="oregan.html" ><-- prev</A> | <A HREF="pramode.html" >next --></A>
</div>
</div>
<div id="navigation">
<a href="../index.html">Home</a>
<a href="../faq/index.html">FAQ</a>
<a href="../lg_index.html">Site Map</a>
<a href="../mirrors.html">Mirrors</a>
<a href="../mirrors.html">Translations</a>
<a href="../search.html">Search</a>
<a href="../archives.html">Archives</a>
<a href="../authors/index.html">Authors</a>
<a href="../contact.html">Contact Us</a>
</div>
<div id="breadcrumbs">
<a href="../index.html">Home</a> >
<a href="index.html">December 2003 (#97)</a> >
Article
</div>
<img src="../gx/2003/sit3-shine.7-2.gif" id="tux" alt="Tux"/>
</body>
</html>
|
