This file documents things you should know to write a new debhelper program. Any program with a name that begins with dh_ should conform to these guidelines (with the historical exception of dh_make). 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/ (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 all options listed in the "SHARED DEBHELPER OPTIONS" section of debhelper(7), including 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. The config file format should be as simple as possible, generally just a list of files to 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. In general, files named debian/*.debhelper are internal to debhelper, and their existence or use should not be relied on by external programs such as the build process of a package. These files will be deleted by dh_clean. Debhelper programs should default to doing exactly what policy says to do. There are always exceptions. Just ask me. Introducing Dh_Lib: ------------------ Dh_Lib is the library used by all debhelper programs to parse their arguments and set some useful variables. It's not mandatory that your program use Dh_Lib.pm, 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. Use Dh_Lib like this: use Debian::Debhelper::Dh_Lib init(); The init() function causes Dh_lib to parse the command line and do some other initialization tasks. 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.pm handles argument processing. Just call init(). You can add support for additional options to your command by passing an options hash to init(). The hash is then passed on the Getopt::Long to parse the command line options. For example, to add a --foo option, which sets $dh{FOO}: init(options => { foo => \$dh{FOO} }); After argument processing, some global variables are used to hold the results; programs can use them later. These variables are elements of the %dh hash. switch variable description -v VERBOSE should the program verbosely output what it is doing? --no-act NO_ACT should the program not actually do anything? -i,-a,-p,-N DOPACKAGES a space delimited list of the binary packages to act on (in Dh_Lib.pm, this is an array) -i DOINDEP set if we're acting on binary independent packages -a DOARCH set if we're acting on binary dependent packages -n NOSCRIPTS if set, do not make any modifications to the package's postinst, postrm, etc scripts. -o ONLYSCRIPTS if set, only make modifications to the package's scripts, but don't look for or install associated files. -X EXCLUDE exclude a something from processing (you decide what this means for your program) (This is an array) -X EXCLUDE_FIND same as EXCLUDE, except all items are put into a string in a way that they will make find find them. (Use ! in front to negate that, of course) Note that this should only be used inside complex_doit(), not in doit(). -d D_FLAG you decide what this means to your program -k K_FLAG used to turn on keeping of something -P TMPDIR package build directory (implies only one package is being acted on) -u U_PARAMS will be set to a string, that is typically parameters your program passes on to some other program. (This is an array) -V V_FLAG will be set to a string, you decide what it means to your program -V V_FLAG_SET will be 1 if -V was specified, even if no parameters were passed along with the -V -A 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 --priority PRIORITY will be set to a number --mainpackage MAINPACKAGE controls which package is treated as the main package to act on --name NAME a name to use for installed files, instead of the package name --error-handler ERROR_HANDLER a function to call on error Any additional command line parameters that do not start with "-" will be ignored, and you can access them later just as you normally would. Global variables: ---------------- The following keys are also set in the %dh hash when you call init(): MAINPACKAGE the name of the first binary package listed in debian/control 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.pm also contains a number of functions you may find useful. doit(@command) Pass this function an array that is a shell command. It will run the command (unless $dh{NO_ACT} is set), and if $dh{VERBOSE} is set, it will also output the command to stdout. You should use this function for almost all commands your program performs that manipulate files in the package build directories. complex_doit($command) Pass this function a string that is a shell command, it will run it similarly to how doit() does. You can pass more complicated commands to this (ie, commands involving piping redirection), however, you have to worry about things like escaping shell metacharacters. verbose_print($message) Pass this command a string, and it will echo it if $dh{VERBOSE} is set. error($errormsg) Pass this command a string, it will output it to standard error and exit. warning($message) Pass this command a string, and it will output it to standard error as a warning message. tmpdir($dir) 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/package". compat($num) Pass this command a number, and if the current compatibility level is less than or equal to that number, it will return true. Looks at DH_COMPAT to get the compatibility level. pkgfile($package, $basename) 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 $dh{MAINPACKAGE}. If the file does not exist, nothing is returned. pkgext($package) 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 $dh{MAINPACKAGE}, it returns nothing (there is no prefix), for the other packages, it returns "package.". isnative($package) Pass this command the name of a package, it returns 1 if the package is a native debian package. As a side effect, $dh{VERSION} is set to the version number of the package. autoscript($package, $scriptname, $snippetname, $sedcommands) Pass parameters: - binary package to be affected - script to add to - filename of snippet - sed commands to run on the snippet. Ie, s/#PACKAGE#/$PACKAGE/ (optional) This command automatically adds shell script snippets to a debian maintainer script (like the postinst or prerm). Note that in v6 mode and up, the snippets are added in reverse order for the removal scripts. dirname($pathname) Return directory part of pathname. basename($pathname) Return base of pathname, addsubstvar($package, $substvar, $deppackage, $verinfo, $remove) This function adds a dependency on some package to the specified substvar in a package's substvar's file. It needs all these parameters: - binary package that gets the item - name of the substvar to add the item to - the package that will be depended on - version info for the package (optional) (ie: ">= 1.1") - if this last parameter is passed, the thing that would be added is removed instead. This can be useful to ensure that a debhelper command is idempotent. (However, we generally don't bother, and rely on the user calling dh_prep.) Note that without this parameter, if you call the function twice with the same values it will only add one item to the substvars file. delsubstvar($package, $substvar) This function removes the entire line for the substvar from the package's shlibs file. excludefile($filename) This function returns true if -X has been used to ask for the file to be excluded. is_udeb($package) Returns true if the package is marked as a udeb in the control file. udeb_filename($package) Returns the filename of the udeb package. getpackages($type) Returns a list of packages in the control file. Pass "arch" or "indep" to specify arch-dependent or -independent. If nothing is specified, returns all packages (including packages that are not built for this architecture). Pass "both" to get the union of "arch" and "indep" packages. As a side effect, populates %package_arches and %package_types with the types of all packages (not only those returned). inhibit_log() Prevent logging the program's successful finish to debian/*debhelper.log load_log($package, $hashref) Loads the log file for the given package and returns a list of logged commands. (Passing a hashref also causes it to populate the hash.) write_log($cmd, $package ...) Writes the log files for the specified package(s), adding the cmd to the end. Sequence Addons: --------------- The dh(1) command has a --with parameter that ca be used to load a sequence addon module named Debian::Debhelper::Sequence::. These modules can add/remove commands to the dh command sequences, by calling some functions from Dh_Lib: insert_before($existing_command, $new_command) Insert $new_command in sequences before $existing_command insert_after($existing_command, $new_command) Insert $new_command in sequences after $existing_command remove_command($existing_command) Remove $existing_command from the list of commands to run in all sequences. add_command($new_command, $sequence) Add $new_command to the beginning of the specified sequence. If the sequence does not exist, it will be created. add_command_options($command, $opt1, $opt2, ...) Append $opt1, $opt2 etc. to the list of additional options which dh passes when running the specified $command. These options are not relayed to debhelper commands called via $command override. remove_command_options($command) Clear all additional $command options previously added with add_command_options(). remove_command_options($command, $opt1, $opt2, ...) Remove $opt1, $opt2 etc. from the list of additional options which dh passes when running the specified $command. Buildsystem Classes: ------------------- The dh_auto_* commands are frontends that use debhelper buildsystem classes. These classes have names like Debian::Debhelper::Buildsystem::foo, and are derived from Debian::Debhelper::Buildsystem, or other, related classes. A buildsystem class needs to inherit or define these methods: DESCRIPTION, check_auto_buildable, configure, build, test, install, clean. See the comments inside Debian::Debhelper::Buildsystem for details. Note that this interface is still subject to change. Note that third-party buildsystems will not automatically be used by default, but can be forced to be used via the --buildsystem parameter. -- Joey Hess