Program to list files of a process in Linux

Question

I need a program to list all the file that are accessed/opened by a process in Linux. It should work like this,

o/p: The full path of the files that the process is accessing.

Don't want to use 'lsof' utility or any other utility.

Is there anyway to achieve this programmatically?

Answer 1

If you want just the files which are accessible thru opened file descriptors by process of pid 1234, list the /proc/1234/fd/ directory (most of the entries are symlinks). You'll also get additional details thru /proc/1234/fdinfo/

Try

ls -l /proc/self/fd/

to get an idea of what these files contain.

Programatically you could use readdir(3) after opendir(3) on these directories (and also readlink(2), at least for entries in /proc/1234/fd/ ....). See also proc(5)

^{Notice that /proc/ is Linux specific. Some other Unixes have it (e.g. Solaris), with very different contents, properties, semantics.}

If you care also about files which have been opened and closed in the past by some process, it is much more difficult. See also inotify(7) and ptrace(2)...

To convert a file path to a "canonical" absolute fiile path, use realpath(3).