See why a program can't seem to access a file

strace php tias.php -e open,access 2>&1 | grep foo.txt
Sometimes a program refuses to read a file and you're not sure why. You may have display_errors turned off for PHP or something. In this example, fopen('/var/www/test/foo.txt') was called but doesn't have read access to foo.txt. Strace can tell you what went wrong. E.g., if php doesn't have read access to the file, strace will say "EACCESS (Permission denied)". Or, if the file path you gave doesn't exist, strace will say "ENOENT (No such file or directory)", etc. This works for any program you can run from the 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 SAPI with diff configs, etc.
Sample Output
open("/var/www/test/filename.txt", O_RDONLY|O_LARGEFILE) = -1 EACCES (Permission denied)

7
By: rkulla
2010-04-20 19:42:42

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