2010-05-05 278 words 2 mins read

$ strace php tias.php -e open,access 2>&1 | <a class="zem_slink freebase/en/grep" href="http://en.wikipedia.org/wiki/Grep" title="Grep" rel="wikipedia">grep foo.txt Sometimes a program refuses to read a file and you&#8217;re not sure why. You may have display_errors turned off for <a class="zem_slink freebase/en/php" href="http://www.php.net/" title="PHP" rel="homepage">PHP or something. In this example, fopen(&#8217;/var/www/test/foo.txt&#8217;) was called but doesn&#8217;t have read access to foo.txt.

Strace can tell you what went wrong. E.g., if php doesn&#8217;t have read access to the file, strace will say &#8221;EACCESS (Permission denied)&#8221;. Or, if the <a class="zem_slink freebase/guid/9202a8c04000641f8000000000220ffa" href="http://en.wikipedia.org/wiki/Path_%28computing%29" title="Path (computing)" rel="wikipedia">file path you gave doesn&#8217;t exist, strace will say &#8221;ENOENT (No such file or directory)&#8221;, etc.

This works for any program you can run from the <a class="zem_slink freebase/en/command_line_interface" href="http://en.wikipedia.org/wiki/Command-line_interface" title="Command-line interface" rel="wikipedia">command-line, e.g., strace python myapp.py -e open,access…

Note: the above command uses php-cli, not mod_php, which is a different <a class="zem_slink freebase/en/server_application_programming_interface" href="http://en.wikipedia.org/wiki/Server_Application_Programming_Interface" title="Server Application Programming Interface" rel="wikipedia">SAPI with <a class="zem_slink freebase/en/diff" href="http://www.tracked.com/company/digg_inc/" title="Diff" rel="tracked">diff configs, etc.

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URL: <a href="http://feedproxy.google.com/%7Er/Command-line-fu/%7E3/Zlwqw2g-10c/find-out-why-a-program-cant-seem-to-access-to-a-file">http://feedproxy.google.com/~r/Command-line-fu/~3/Zlwqw2g-10c/find-out-why-a-program-cant-seem-to-access-to-a-file<h6 class="zemanta-related-title">Related articles by Zemanta <ul class="zemanta-article-ul"> <li class="zemanta-article-ul-li"><a href="http://blog.amit-agarwal.co.in/2010/04/12/visualizing-system-performance-data/">Visualizing system performance data (amit-agarwal.co.in) <li class="zemanta-article-ul-li"><a href="http://insidehpc.com/2010/03/17/io-profiling-of-mpi-apps/">IO profiling of MPI apps (insidehpc.com) <li class="zemanta-article-ul-li"><a href="http://www.slideshare.net/fabpot/symfony-components-3393116">Symfony Components (slideshare.net) <li class="zemanta-article-ul-li"><a href="http://www.skorks.com/2010/05/what-every-developer-should-know-about-urls/">What Every Developer Should Know About URLs (skorks.com) <li class="zemanta-article-ul-li"><a href="http://helpdeskgeek.com/databases/create-mysql-stored-routines-tips-tricks/">Creating MySQL Stored Routines for Non-DBAs – Part Three (helpdeskgeek.com) <div class="zemanta-pixie"><a class="zemanta-pixie-a" href="http://reblog.zemanta.com/zemified/d00c0d37-773d-43e5-ac21-e9afbd6b2dd2/" title="Reblog this post [with Zemanta]"><img class="zemanta-pixie-img" src="http://blog.amit-agarwal.co.in/wp-content/uploads/2010/08/reblog_b78.png" alt="Reblog this post [with Zemanta]" /><span class="zem-script more-related more-info pretty-attribution paragraph-reblog">


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Authored By Amit Agarwal

Amit Agarwal, Linux and Photography are my hobbies.Creative Commons Attribution 4.0 International License.

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