ftw/nftw -- filesystem tree walk

odys · March 18, 2008, 5:50pm

Hi,

I recently experimented with ftw() and nftw(). These are function for calling some function for every
file in a subtree.
I need to get full information about type of file.
Almost everything is working according to documentation
but I noticed following problem:

With a value FTW_PHYS as 4th arg. for nftw() the callback should obtain FTW_SL for proper symbolic links and FTW_SLN for dangling ones. I always obtain FTW_SL - this is bug in my opinion.

So I need to supply 0 as 4th arg. Then callbacks [correctly] obtain FTW_F for proper symbolic links and FTW_SLN for dangling ones. Unfortunately 'struct stat' callback obtains also returns same 'st_mode' value for regular files and symbolic links (due to stat() instead of lstat() in implementation probably) and I need to call lstat() additionally. This workaround works.

Have anybody obtained FTW_SLN in FTW_PHYS mode?
I am using glibc 2.3.5 and have not found any information about bugs.

thanks,

shamrock · March 18, 2008, 6:10pm

What hardware platform and OS are you talking about? Otherwise your program is reporting the correct thing. If the FTW_PHYS flag is given as the 4th argument...FTW_SL files will be reported but not FTW_SLN types unless the 4th arg is not FTW_PHYS.

odys · March 18, 2008, 6:24pm

I am using Slackware Linux 10.2 / glibc 2.3.5 (PC machine).

From the 'info' documentation:

&gt;\`FTW_PHYS'
      &gt;While traversing the directory symbolic links are not
      &gt;followed.  Instead symbolic links are reported using the
      &gt;\`FTW_SL' value for the type parameter to the callback
      &gt;function.  If the file referenced by a symbolic link does  not
      &gt;exist \`FTW_SLN' is returned instead.

Therefore I understand with FTW_PHYS I will have FTW_SL or FTW_SLN given correctly, and FTW_F cannot happen for links.