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</style>

<title>git-bisect(1)</title>

</head>

<body>

<h1>

git-bisect(1) Manual Page

</h1>

<p>git-bisect -

Find by binary search the change that introduced a bug

</p>

</div>

<h2>SYNOPSIS</h2>

<div class="para"><p><em>git bisect</em> <subcommand> <options></p></div>

</div>

<h2 id="_description">DESCRIPTION</h2>

<div class="para"><p>The command takes various subcommands, and different options depending

on the subcommand:</p></div>

<pre><tt>git bisect help

git bisect start [<bad> [<good>...]] [--] [<paths>...]

git bisect bad [<rev>]

git bisect good [<rev>...]

git bisect skip [(<rev>|<range>)...]

git bisect reset [<commit>]

git bisect visualize

git bisect replay <logfile>

git bisect log

git bisect run <cmd>...</tt></pre>

</div></div>

<div class="para"><p>This command uses <em>git rev-list --bisect</em> to help drive the

binary search process to find which change introduced a bug, given an

old "good" commit object name and a later "bad" commit object name.</p></div>

<h3 id="_getting_help">Getting help</h3><div style="clear:left"></div>

<div class="para"><p>Use "git bisect" to get a short usage description, and "git bisect

help" or "git bisect -h" to get a long usage description.</p></div>

<h3 id="_basic_bisect_commands_start_bad_good">Basic bisect commands: start, bad, good</h3><div style="clear:left"></div>

<div class="para"><p>Using the Linux kernel tree as an example, basic use of the bisect

command is as follows:</p></div>

<pre><tt>$ git bisect start

$ git bisect bad # Current version is bad

$ git bisect good v2.6.13-rc2 # v2.6.13-rc2 was the last version

# tested that was good</tt></pre>

</div></div>

<div class="para"><p>When you have specified at least one bad and one good version, the

command bisects the revision tree and outputs something similar to

the following:</p></div>

<pre><tt>Bisecting: 675 revisions left to test after this</tt></pre>

</div></div>

<div class="para"><p>The state in the middle of the set of revisions is then checked out.

You would now compile that kernel and boot it. If the booted kernel

works correctly, you would then issue the following command:</p></div>

<pre><tt>$ git bisect good # this one is good</tt></pre>

</div></div>

<div class="para"><p>The output of this command would be something similar to the following:</p></div>

<pre><tt>Bisecting: 337 revisions left to test after this</tt></pre>

</div></div>

<div class="para"><p>You keep repeating this process, compiling the tree, testing it, and

depending on whether it is good or bad issuing the command "git bisect good"

or "git bisect bad" to ask for the next bisection.</p></div>

<div class="para"><p>Eventually there will be no more revisions left to bisect, and you

will have been left with the first bad kernel revision in "refs/bisect/bad".</p></div>

<h3 id="_bisect_reset">Bisect reset</h3><div style="clear:left"></div>

<div class="para"><p>After a bisect session, to clean up the bisection state and return to

the original HEAD, issue the following command:</p></div>

<pre><tt>$ git bisect reset</tt></pre>

</div></div>

<div class="para"><p>By default, this will return your tree to the commit that was checked

out before <tt>git bisect start</tt>. (A new <tt>git bisect start</tt> will also do

that, as it cleans up the old bisection state.)</p></div>

<div class="para"><p>With an optional argument, you can return to a different commit

instead:</p></div>

<pre><tt>$ git bisect reset <commit></tt></pre>

</div></div>

<div class="para"><p>For example, <tt>git bisect reset HEAD</tt> will leave you on the current

bisection commit and avoid switching commits at all, while <tt>git bisect

reset bisect/bad</tt> will check out the first bad revision.</p></div>

<h3 id="_bisect_visualize">Bisect visualize</h3><div style="clear:left"></div>

<div class="para"><p>To see the currently remaining suspects in <em>gitk</em>, issue the following

command during the bisection process:</p></div>

<pre><tt>$ git bisect visualize</tt></pre>

</div></div>

<div class="para"><p><tt>view</tt> may also be used as a synonym for <tt>visualize</tt>.</p></div>

<div class="para"><p>If the <em>DISPLAY</em> environment variable is not set, <em>git log</em> is used

instead. You can also give command line options such as <tt>-p</tt> and

<pre><tt>$ git bisect view --stat</tt></pre>

</div></div>

<h3 id="_bisect_log_and_bisect_replay">Bisect log and bisect replay</h3><div style="clear:left"></div>

<div class="para"><p>After having marked revisions as good or bad, issue the following

command to show what has been done so far:</p></div>

<pre><tt>$ git bisect log</tt></pre>

</div></div>

<div class="para"><p>If you discover that you made a mistake in specifying the status of a

revision, you can save the output of this command to a file, edit it to

remove the incorrect entries, and then issue the following commands to

return to a corrected state:</p></div>

<pre><tt>$ git bisect reset

$ git bisect replay that-file</tt></pre>

</div></div>

<h3 id="_avoiding_testing_a_commit">Avoiding testing a commit</h3><div style="clear:left"></div>

<div class="para"><p>If, in the middle of a bisect session, you know that the next suggested

revision is not a good one to test (e.g. the change the commit

introduces is known not to work in your environment and you know it

does not have anything to do with the bug you are chasing), you may

want to find a nearby commit and try that instead.</p></div>

<div class="para"><p>For example:</p></div>

<pre><tt>$ git bisect good/bad # previous round was good or bad.

Bisecting: 337 revisions left to test after this

$ git bisect visualize # oops, that is uninteresting.

$ git reset --hard HEAD~3 # try 3 revisions before what

# was suggested</tt></pre>

</div></div>

<div class="para"><p>Then compile and test the chosen revision, and afterwards mark

the revision as good or bad in the usual manner.</p></div>

<h3 id="_bisect_skip">Bisect skip</h3><div style="clear:left"></div>

<div class="para"><p>Instead of choosing by yourself a nearby commit, you can ask git

to do it for you by issuing the command:</p></div>

<pre><tt>$ git bisect skip # Current version cannot be tested</tt></pre>

</div></div>

<div class="para"><p>But git may eventually be unable to tell the first bad commit among

a bad commit and one or more skipped commits.</p></div>

<div class="para"><p>You can even skip a range of commits, instead of just one commit,

using the "<em><commit1></em>..<em><commit2></em>" notation. For example:</p></div>

<pre><tt>$ git bisect skip v2.5..v2.6</tt></pre>

</div></div>

<div class="para"><p>This tells the bisect process that no commit after <tt>v2.5</tt>, up to and

including <tt>v2.6</tt>, should be tested.</p></div>

<div class="para"><p>Note that if you also want to skip the first commit of the range you

would issue the command:</p></div>

<pre><tt>$ git bisect skip v2.5 v2.5..v2.6</tt></pre>

</div></div>

<div class="para"><p>This tells the bisect process that the commits between <tt>v2.5</tt> included

and <tt>v2.6</tt> included should be skipped.</p></div>

<h3 id="_cutting_down_bisection_by_giving_more_parameters_to_bisect_start">Cutting down bisection by giving more parameters to bisect start</h3><div style="clear:left"></div>

<div class="para"><p>You can further cut down the number of trials, if you know what part of

the tree is involved in the problem you are tracking down, by specifying

path parameters when issuing the <tt>bisect start</tt> command:</p></div>

<pre><tt>$ git bisect start -- arch/i386 include/asm-i386</tt></pre>

</div></div>

<div class="para"><p>If you know beforehand more than one good commit, you can narrow the

bisect space down by specifying all of the good commits immediately after

the bad commit when issuing the <tt>bisect start</tt> command:</p></div>

<pre><tt>$ git bisect start v2.6.20-rc6 v2.6.20-rc4 v2.6.20-rc1 --

# v2.6.20-rc6 is bad

# v2.6.20-rc4 and v2.6.20-rc1 are good</tt></pre>

</div></div>

<h3 id="_bisect_run">Bisect run</h3><div style="clear:left"></div>

<div class="para"><p>If you have a script that can tell if the current source code is good

or bad, you can bisect by issuing the command:</p></div>

<pre><tt>$ git bisect run my_script arguments</tt></pre>

</div></div>

<div class="para"><p>Note that the script (<tt>my_script</tt> in the above example) should

exit with code 0 if the current source code is good, and exit with a

code between 1 and 127 (inclusive), except 125, if the current

source code is bad.</p></div>

<div class="para"><p>Any other exit code will abort the bisect process. It should be noted

that a program that terminates via "exit(-1)" leaves $? = 255, (see the

exit(3) manual page), as the value is chopped with "& 0377".</p></div>

<div class="para"><p>The special exit code 125 should be used when the current source code

cannot be tested. If the script exits with this code, the current

revision will be skipped (see <tt>git bisect skip</tt> above).</p></div>

<div class="para"><p>You may often find that during a bisect session you want to have

temporary modifications (e.g. s/#define DEBUG 0/#define DEBUG 1/ in a

header file, or "revision that does not have this commit needs this

patch applied to work around another problem this bisection is not

interested in") applied to the revision being tested.</p></div>

<div class="para"><p>To cope with such a situation, after the inner <em>git bisect</em> finds the

next revision to test, the script can apply the patch

before compiling, run the real test, and afterwards decide if the

revision (possibly with the needed patch) passed the test and then

rewind the tree to the pristine state. Finally the script should exit

with the status of the real test to let the "git bisect run" command loop

determine the eventual outcome of the bisect session.</p></div>

</div>

<h2 id="_examples">EXAMPLES</h2>

<li>

<p>

Automatically bisect a broken build between v1.2 and HEAD:

</p>

<pre><tt>$ git bisect start HEAD v1.2 -- # HEAD is bad, v1.2 is good

$ git bisect run make # "make" builds the app</tt></pre>

</div></div>

</li>

<li>

<p>

Automatically bisect a test failure between origin and HEAD:

</p>

<pre><tt>$ git bisect start HEAD origin -- # HEAD is bad, origin is good

$ git bisect run make test # "make test" builds and tests</tt></pre>

</div></div>

</li>

<li>

<p>

Automatically bisect a broken test suite:

</p>

<pre><tt>$ cat ~/test.sh

#!/bin/sh

make || exit 125 # this skips broken builds

make test # "make test" runs the test suite

$ git bisect start v1.3 v1.1 -- # v1.3 is bad, v1.1 is good

$ git bisect run ~/test.sh</tt></pre>

</div></div>

<div class="para"><p>Here we use a "test.sh" custom script. In this script, if "make"

fails, we skip the current commit.</p></div>

<div class="para"><p>It is safer to use a custom script outside the repository to prevent

interactions between the bisect, make and test processes and the

script.</p></div>

<div class="para"><p>"make test" should "exit 0", if the test suite passes, and

"exit 1" otherwise.</p></div>

</li>

<li>

<p>

Automatically bisect a broken test case:

</p>

<pre><tt>$ cat ~/test.sh

#!/bin/sh

make || exit 125 # this skips broken builds

~/check_test_case.sh # does the test case passes ?

$ git bisect start HEAD HEAD~10 -- # culprit is among the last 10

$ git bisect run ~/test.sh</tt></pre>

</div></div>

<div class="para"><p>Here "check_test_case.sh" should "exit 0" if the test case passes,

and "exit 1" otherwise.</p></div>

<div class="para"><p>It is safer if both "test.sh" and "check_test_case.sh" scripts are

outside the repository to prevent interactions between the bisect,

make and test processes and the scripts.</p></div>

</li>

<li>

<p>

Automatically bisect a broken test suite:

</p>

<pre><tt>$ git bisect start HEAD HEAD~10 -- # culprit is among the last 10

$ git bisect run sh -c "make || exit 125; ~/check_test_case.sh"</tt></pre>

</div></div>

<div class="para"><p>Does the same as the previous example, but on a single line.</p></div>

</li>

</ul></div>

</div>

<h2 id="_author">Author</h2>

<div class="para"><p>Written by Linus Torvalds <torvalds@osdl.org></p></div>

</div>

<h2 id="_documentation">Documentation</h2>

<div class="para"><p>Documentation by Junio C Hamano and the git-list <git@vger.kernel.org>.</p></div>

</div>

<div class="para"><p><a href="git-bisect-lk2009.html">Fighting regressions with git bisect</a>,

<a href="git-blame.html">git-blame(1)</a>.</p></div>

</div>

<div class="para"><p>Part of the <a href="git.html">git(1)</a> suite</p></div>

</div>

Last updated 2010-09-18 23:56:34 UTC

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