Advanced Scripting in Barabash

Setting environemt variables

It is possible to set build parameters (called also environment variables) in four ways. They are set in following order:

Parameters in command line

Build parameters can be set in command line which executes Barabash script.

Example:

./build.py CC=/usr/bin/icc

Global variables

Build parameters can also be set as globals in Barabash script.

Example:

CC = "/usr/bin/icc"
objects = MapOp("objects", src, "%.o:%.c", "{CC} -c {in} -o {out}")

barabash.core.set_env() function

Beside setting build parameters as globals it is also possible to set then in a script using barabash.core.set_env() function.

Example:

set_env("CC", "/usr/bin/icc")
objects = MapOp("objects", src, "%.o:%.c", "{CC} -c {in} -o {out}")

Parameters from environment

The last form of setting build parameters is inheriting them from process environment. This way has the lowest precedence.

Example:

export CC=/usr/bin/icc
./build.py

or:

CC=/usr/bin/icc ./build.py

Variables in Bash actions

Bash actions are able to use environment variables. There are two types of environment variables:

  • predefined variables
  • user defined variables

The can be accessed in Bash action string using curly brackets:

"{CC} -c {in} -o {out}"

Predefined variables

There are two built-in variables:
  • in
  • out

in and out are available in all operations beside barabash.core.Command.

in is an input to operation. In case of barabash.core.MapOp operation in is a file while in barabash.core.ReduceOp operation it is a list of files.

out is a full path to output file of an operation.

User defined variables

There can be defined additional variables by user. It can be made in several ways what was already described in previous chapter.

Variables’ methods

It is possible to modify a variable’s values in Bash action using several methods. The following methods are available:

  • all from os.path module, e.g. dirname which returns the directory component of a pathname
  • dropext, returns filename without extension (e.g. w/o .jpg)
  • dropext2, drops file extensions twice (e.g. .aa.bb)

These methods can be applied to all variables. In the case when a values of a variable is a list then the method is executed for each element on the list.

Example:

ReduceOp("js.tar.gz", src_js, "tar -C {srcdir} -zcvf {out} {in.basename}")

Another example:

"""
{CC} -shared -Wl,-soname,{out.dropext} -o {out} {in}
ln -f -s {out} {out.dropext}
ln -f -s {out} {out.dropext2}
"""

Custom Operations

Custom behavior of operation can be implement by extending one of basic operation classes:
The following methods of these classes can be overriden to get additional behavior:
  • __init__(self, ...)
  • action(self, env)
  • indirect_deps(self, env)

__init__(self, ...)

Example:

class BuildStaticLib(core.ReduceOp):
    def __init__(self, name, sources):
        objs = Compile(name + "_compile", sources)
        super(BuildStaticLib, self).__init__(name, objs, """{AR} cru {out} {in}
                                                            {RANLIB} {out}""")

In __init__(self, ...) there can be added some additional instructions. In the example there is injected additional operation (Compile) so actually the whole operation barabash.ops.BuildStaticLib comprises two operations: compiling and linking static library. In __init__(self, ...) the initialzer of super class should be always run. In this case it is an initializer of barabash.core.ReduceOp with appropriate arguments.

action(self, env)

Beside declaring action as function or Bash script it is also possible to directly override action in Operation subclass. A helper method barabash.core.Operation.run_script() is available for executing Bash script provided as string.

indirect_deps(self, env)

Another method which can be overriden is barabash.core.Operation.indirect_deps(). It allows providing additional indirect dependencies, e.g. .h header files that are included by .c source files.

Modules

Barabash support more complex projects by providing modules. This allows defining build sub-script for each nested component in the project.

Sample nested project:

prog
 |--- bb-prog.py
 |--- main.c
 |--- liba
 |     |--- main.c
 |     |--- bb-liba.py
 |--- libb
       |--- bb-libb.py
       |--- b.c
       |--- b.h

main.c is a top level source of a prog program and bb-prog.py is top level Barabash script. liba is a static library which is linked into prog. libb is a dynamic library that prog is linking with.

bb-prog.py:

from barabash import include, BuildProgram, run

liba = include("liba/bb-liba.py")
libb = include("libb/bb-libb.py")

CFLAGS = "-DAAA=1"

BuildProgram("prog", "main.c", static_libs=liba.liba, shared_libs=libb.libb, external_libs=["m"])

run()

barabash.core.include() function is used to include modules. Then, included modules can be referenced in operations as dependencies and inputs.

liba/bb-liba.py:

from barabash import BuildStaticLib

liba = BuildStaticLib("liba.a", "main.c")

libb/bb-libb.py:

from barabash import BuildSharedLib

libb = BuildSharedLib("libb.so.1.0", "b.c")

Built-in targets

There are several built-in targets in Barabash:

  • help
  • env

help

help target displays all availables targets in Barabash script:

$ ./build.py help
Barabash script for Barabash
Barabash Help:
upload-website
    combine-website
        build-docs
        render-website
        tests
 build-pkg
 upload-pkg

env

env target display all Barabash variables that are set directly and indirectly:

$ ./build.py env AAAA=bar
Barabash script for Barabash
Barabash Environment:
                      AAAA   bar
                        AR   ar
                        CC   gcc
                 COLORTERM   gnome-terminal
           DESKTOP_SESSION   ubuntu
                   DISPLAY   :0
                GDMSESSION   ubuntu
                      HOME   /home/godfryd
                      LANG   pl_PL.UTF-8
                   LOGNAME   godfryd
                      PATH   /usr/sbin:/usr/bin:/sbin:/bin
                       PWD   /home/godfryd/repos/barabash2
                    RANLIB   ranlib
                     SHELL   /bin/bash
                     SHLVL   1
             SSH_AGENT_PID   1929
             SSH_AUTH_SOCK   /tmp/keyring-VUwQmc/ssh
                      TERM   xterm
                      USER   godfryd
                  USERNAME   godfryd
                  WINDOWID   62914564
                XAUTHORITY   /home/godfryd/.Xauthority




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