summaryrefslogtreecommitdiff
path: root/PROGRAMMING
blob: 7dc0c638e944e85cfb42e7099fbd827bea12963f (plain)
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
This file documents things you should know to write a new debhelper program.

Standardization:
---------------

There are lots of debhelper commands. To make the learning curve shallower,
I want them all to behave in a standard manner:

All debhelper programs have names beginning with "dh_". This is so we don't
pollute the name space too much.

Debhelper programs should never output anything to standard output except
error messages, important warnings, and the actual commands they run that
modify files under debian/ and debian/tmp, etc (this last only if they are
passed -v, and if you output the commands, you should indent them with 1 tab). 
This is so we don't have a lot of noise output when all the debhelper commands
in a debian/rules are run, so the important stuff is clearly visible.

Debhelper programs should accept the options, -v, -i, -a, -p, --no-act, and
-P, and any long forms of these options, like --verbose . If necessary, the
options may be ignored.

If debhelper commands need config files, they should use
debian/package.filename as the name of the config file (replace filename
with whatever your command wants), and debian/filename should also be
checked for config information for the first binary package in
debian/control. Also, debhelper commands should accept the same sort of
information that appears in the config files, on their command lines, if
possible, and apply that information to the first package they act on.

Debhelper programs should never modify the debian/postinst, debian/prerm,
etc scripts, instead, they can add lines to debian/postinst.debhelper, etc. 
The autoscript() function (see below) is one easy way to do this.
dh_installdeb is an exception, it will run after the other commands and
merge these modifications into the actual postinst scripts.

There are always exceptions. Just ask me.

Introducing dh_lib:
------------------

All debhelper programs use the dh_lib library (actually it's a shell script)
to parse their arguments and set some useful variables. It's not mandatory
that your program use dh_lib, but it will make it a lot easier to keep it in
sync with the rest of debhelper if it does, so this is highly encouraged.

Typically, you invoke dh_lib like this:

PATH=debian:$PATH:/usr/lib/debhelper
. dh_lib

The path statement is there to make your program look first in debian/ for
dh_lib (so users can install a modified version there if necessary), then the
rest of the path, then the canonical location of dh_lib, /usr/lib/debhelper.

Argument processing:
-------------------

All debhelper programs should respond to certain arguments, such as -v, -i,
-a, and -p. To help you make this work right, dh_lib handles argument
processing.

As soon as dh_lib loads, it processes any arguments that have been passed to
your program. The following variables may be set during this stage; your
program can use them later:

switch		variable	description
-v		DH_VERBOSE	should the program verbosely output what it is
				doing?
--no-act	DH_NO_ACT	should the program not actually do anything?
-i,-a,-p	DH_DOPACKAGES	a space delimited list of the binary packages
				to act on
-i,-p		DH_DOINDEP	a space delimited list of the binary independent
				packages to act on
-a,-p		DH_DOARCH	a space delimited list of the binary dependent
				packages to act on
-n		DH_NOSCRIPTS	if set, do not make any modifications to the 
				package's postinst, postrm, etc scripts.
-X		DH_EXCLUDE	exclude a something from processing (you
				decide what this means for your program)
		DH_EXCLUDE_GREP	same as DH_EXCLUDE, except all items are
				separated by '|' characters, instead of spaces,
				handy for egrep -v
-x		DH_INCLUDE_CONFFILES
				include conffiles. It's -x for obscure
				historical reasons.
-d		DH_D_FLAG	you decide what this means to your program
-r		DH_R_FLAG	you decide what this means to your program
-k		DH_K_FLAG	you decide what this means to your program
-P		DH_TMPDIR	package build directory (implies only one
				package is being acted on)
-u		DH_U_PARAMS	will be set to a string, that is typically
				parameters your program passes on to some
				other program.
-m		DH_M_PARAMS	will be set to a string, you decide what it
				means to your program
-V		DH_V_FLAG	will be set to a string, you decide what it
				means to your program
-V		DH_V_FLAG_SET	will be 1 if -V was specified, even if no
				parameters were passed along with the -V
-A		DH_PARAMS_ALL	generally means that additional command line
				parameters passed to the program (other than
				those processed here), will apply to all 
				binary packages the program acts on, not just
				the first
--init-script	DH_INIT_SCRIPT	will be set to a string, which specifies an
				init script name (probably only
				dh_installinit will ever use this)

Any additional command line parameters that do not start with "-" will be 
ignored, and you can access them later just as you normally would ($1, $2,
etc).

If you need a new command line option, just ask me, and I will add it.

Global variables:
----------------

The following variables are also set, you can use any of them:

MAINPACKAGE	the name of the first binary package listed in
		debian/control
DH_FIRSTPACKAGE	the first package we were instructed to act on. This package
		typically gets special treatment, additional arguments
		specified on the command line may effect it.

Functions:
---------

Dh_lib also contains a number of functions you may find useful.

doit()
	Pass this function a string that is a shell command. It will run the
	command (unless DH_NO_ACT is set), and if DH_VERBOSE is set, it will
	also output the command to stdout. You should use this function for
	almost all commands your program performs that manipulate files in
	the package build directories.
complex_doit()
	This is the same as doit(), except you can pass more complicated
	commands to it (ie, commands involving piping redirection)
verbose_echo()
	Pass this command a string, and it will echo it if DH_VERBOSE is set.
error()
	Pass this command a string, it will output it to standard error and
	exit.
warning()
	Pass this command a string, and it will output it to standard error
	as a warning message.
tmpdir()
	Pass this command the name of a binary package, it will return the
	name of the tmp directory that will be used as this package's
	package build directory. Typically, this will be "debian/tmp" or
	"debian/package".
pkgfile()
	Pass this command the name of a binary package, and the base name of a
	file, and it will return the actual filename to use. This is used
	for allowing debhelper programs to have configuration files in the
	debian/ directory, so there can be one config file per binary
	package. The convention is that the files are named
	debian/package.filename, and debian/filename is also allowable for
	the MAINPACKAGE. If the file does not exist, nothing is returned.
pkgext()
	Pass this command the name of a binary package, and it will return
	the name to prefix to files in debian/ for this package. For the
	MAINPACKAGE, it returns nothing (there is no prefix), for the other
	packages, it returns "package.".
isnative()
	Pass this command the name of a package, it returns 1 if the package
	is a native debian package.
	As a side effect, VERSION is set to the version number of the
	package.
autoscript()
	Pass 3 parameters:
	 1: script to add to
	 2: filename of snippet
	 3: sed commands to run on the snippet. Ie, s/#PACKAGE#/$PACKAGE/
	    (optional)
	This command automatically adds shell script snippets to a debian
	maintainer script (like the postinst or prerm).

Notes:
-----

Dh_lib is still evolving.
There will probably be a perl version too, in the future.

-- Joey Hess <joeyh@master.debian.org>