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| 1 | <html> | ||
| 2 | <head> | ||
| 3 | <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> | ||
| 4 | <title>6.5. Running a Task</title> | ||
| 5 | <link rel="stylesheet" type="text/css" href="../book.css"> | ||
| 6 | <meta name="generator" content="DocBook XSL Stylesheets V1.76.1"> | ||
| 7 | <link rel="home" href="index.html" title="The Yocto Project Reference Manual"> | ||
| 8 | <link rel="up" href="ref-bitbake.html" title="Chapter 6. BitBake"> | ||
| 9 | <link rel="prev" href="ref-bitbake-tasklist.html" title="6.4. The Task List"> | ||
| 10 | <link rel="next" href="ref-bitbake-commandline.html" title="6.6. BitBake Command Line"> | ||
| 11 | </head> | ||
| 12 | <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="section" title="6.5. Running a Task"> | ||
| 13 | <div class="titlepage"><div><div><h2 class="title" style="clear: both"> | ||
| 14 | <a name="ref-bitbake-runtask"></a>6.5. Running a Task</h2></div></div></div> | ||
| 15 | <p> | ||
| 16 | Tasks can either be a shell task or a Python task. | ||
| 17 | For shell tasks, BitBake writes a shell script to | ||
| 18 | <code class="filename">${WORKDIR}/temp/run.do_taskname.pid</code> and then executes the script. | ||
| 19 | The generated shell script contains all the exported variables, and the shell functions | ||
| 20 | with all variables expanded. | ||
| 21 | Output from the shell script goes to the file <code class="filename">${WORKDIR}/temp/log.do_taskname.pid</code>. | ||
| 22 | Looking at the expanded shell functions in the run file and the output in the log files | ||
| 23 | is a useful debugging technique. | ||
| 24 | </p> | ||
| 25 | <p> | ||
| 26 | For Python tasks, BitBake executes the task internally and logs information to the | ||
| 27 | controlling terminal. | ||
| 28 | Future versions of BitBake will write the functions to files similar to the way | ||
| 29 | shell tasks are handled. | ||
| 30 | Logging will be handled in way similar to shell tasks as well. | ||
| 31 | </p> | ||
| 32 | <p> | ||
| 33 | Once all the tasks have been completed BitBake exits. | ||
| 34 | </p> | ||
| 35 | <p> | ||
| 36 | When running a task, BitBake tightly controls the execution environment | ||
| 37 | of the build tasks to make sure unwanted contamination from the build machine | ||
| 38 | cannot influence the build. | ||
| 39 | Consequently, if you do want something to get passed into the build | ||
| 40 | task's environment, you must take a few steps: | ||
| 41 | </p> | ||
| 42 | <div class="orderedlist"><ol class="orderedlist" type="1"> | ||
| 43 | <li class="listitem"> | ||
| 44 | <p>Tell BitBake to load what you want from the environment | ||
| 45 | into the data store. | ||
| 46 | You can do so through the <code class="filename">BB_ENV_EXTRAWHITE</code> | ||
| 47 | variable. | ||
| 48 | For example, assume you want to prevent the build system from | ||
| 49 | accessing your <code class="filename">$HOME/.ccache</code> directory. | ||
| 50 | The following command tells BitBake to load | ||
| 51 | <code class="filename">CCACHE_DIR</code> from the environment into the data | ||
| 52 | store: | ||
| 53 | </p> | ||
| 54 | <pre class="literallayout"> | ||
| 55 | export BB_ENV_EXTRAWHITE="$BB_ENV_EXTRAWHITE CCACHE_DIR" | ||
| 56 | </pre> | ||
| 57 | </li> | ||
| 58 | <li class="listitem"> | ||
| 59 | <p>Tell BitBake to export what you have loaded into the | ||
| 60 | environment store to the task environment of every running task. | ||
| 61 | Loading something from the environment into the data store | ||
| 62 | (previous step) only makes it available in the datastore. | ||
| 63 | To export it to the task environment of every running task, | ||
| 64 | use a command similar to the following in your | ||
| 65 | <code class="filename">local.conf</code> or distro configuration file: | ||
| 66 | </p> | ||
| 67 | <pre class="literallayout"> | ||
| 68 | export CCACHE_DIR | ||
| 69 | </pre> | ||
| 70 | </li> | ||
| 71 | </ol></div> | ||
| 72 | <p> | ||
| 73 | </p> | ||
| 74 | <div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"> | ||
| 75 | <h3 class="title">Note</h3> | ||
| 76 | A side effect of the previous steps is that BitBake records the variable | ||
| 77 | as a dependency of the build process in things like the shared state | ||
| 78 | checksums. | ||
| 79 | If doing so results in unnecessary rebuilds of tasks, you can whitelist the | ||
| 80 | variable so that the shared state code ignores the dependency when it creates | ||
| 81 | checksums. | ||
| 82 | For information on this process, see the <code class="filename">BB_HASHBASE_WHITELIST</code> | ||
| 83 | example in the "<a class="link" href="checksums.html" title="3.2.2. Checksums (Signatures)">Checksums (Signatures)</a>" section. | ||
| 84 | </div> | ||
| 85 | </div></body> | ||
| 86 | </html> | ||