Hi Steve,
Thanks for the response.But how will lsof work for a particular PID.If
lsof can print all the files by their names then why can't any c
program?The idea was to prove that the file /dev/pts/9 or some no. is
opened by the bash and to it are the stdin,stdout and stderr
associated.For that ,the fds 0,1,and 2 are supposed to point to the same
file /dev/pts/9 or say /dev/tty3 ....
This can be proved using lsof -p <PID OF THE BASH> .But how to prove
that from within a c program?This lead to the sol if we can get the
filename from the file descriptor and print it on the screen.
regards-
kaushal.
On Thu, 2005-04-14 at 16:07, Steve Graegert wrote:
> On 4/14/05, kaushal <[EMAIL PROTECTED]> wrote:
> > Hello all,
> > How can I get the filename/pathname given the open file
> > descriptor?Does
> > fstat provide this feature internally?Can somebody give the code snippet
> > for this.
>
> There is no such thing. It is not possible to obtain a FD's filename
> reliably. Unless you are absolutely sure that this particular FD
> points to a file (or directory) and not to a socket, pipe or
> something similar, you will not be able to use fstat reliably. Which
> of stat's fields are suggesting to be helpful reagarding to your
> problem? st_ino? How would you locate a file based on its file ID?
> This would require scanning the complete file system (and probably
> more than one). Another problem is, that an FD might be associated
> with other files at the same time or files can be stored inside a
> directory that you can't read due to lack of sufficient permissions.
> What you are looking for is some kind of reverse lookup to unwind the
> many-to-one relationship of files and inodes.
>
> A couple of years ago Floyd Davidson suggested some code that may
> point you to the right direction (not tested):
>
> /* A demo program to locate file names related to an inode number */
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <unistd.h>
> #include <string.h>
> #include <sys/stat.h>
> #include <dirent.h>
> #include <limits.h>
>
> void scan_list(char *curdir, struct dirent **ptr_nl, int dirs);
> int file_select(const struct dirent *nl);
>
> ino_t inode;
> char curdir[PATH_MAX] = "."; /* default search directory */
>
> int
> main(int argc, char **argv)
> {
> struct dirent **namelist;
> struct stat st;
>
> if (argc < 2 || argc > 3) {
> fprintf(stderr,"usage: %s inode [directory]\n", argv[0]);
> exit(EXIT_FAILURE);
> }
> inode = strtoul(argv[1], NULL, 10);
> if (!inode) {
> fprintf(stderr,"Error: invalid inode\n");
> exit(EXIT_FAILURE);
> }
> if (argc == 3 && !lstat(argv[2], &st) && S_ISDIR(st.st_mode)) {
> strcpy(curdir, argv[2]);
> }
>
> scan_list(curdir, namelist,
> scandir(curdir, &namelist, file_select, alphasort));
> return EXIT_SUCCESS;
> }
>
> /*
> * returns 1 for directories, otherwise 0
> * and displays any filename which matches inode.
> */
> int
> file_select(const struct dirent *nl)
> {
> struct stat st;
> char curfile[PATH_MAX];
>
> sprintf(curfile, "%s/%s", curdir, nl->d_name);
> if (0 == lstat(curfile, &st)) {
> /* report a matching inode number */
> if (st.st_ino == inode) {
> printf(" %6lu %-20s \n", (unsigned long) st.st_ino, curfile);
> }
> /* skip these directories */
> if (!strcmp(nl->d_name, ".") || !strcmp(nl->d_name, "..")) {
> return 0;
> }
> /* otherwise list all directories */
> if (S_ISDIR(st.st_mode)) {
> return 1;
> }
> } return 0;
> }
>
> /* descend through all directories */
> void
> scan_list(char *olddir, struct dirent **ptr_nl, int dirs)
> {
> char savedir[PATH_MAX];
> int i;
> struct dirent **namelist;
>
> if (dirs > 0) {
> for (i = 0; i < dirs; ++i) {
> strcpy(savedir, curdir);
> sprintf(curdir,"%s/%s", olddir, ptr_nl[i]->d_name);
> scan_list(curdir, namelist,
> scandir(curdir, &namelist, file_select, alphasort));
> strcpy(curdir, savedir);
> }
> }
> }
>
> /* End of demo program */
>
> Kind Regards
>
> \Steve
>
> --
>
> Steve Graegert <[EMAIL PROTECTED]>
> Independent Software Consultant {C/C++ && Java && .NET}
> Mobile: +49 (176) 21 24 88 69
> Office: +49 (9131) 71 26 40 9
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