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How to assign needed file descriptor to a file (edit)
Revision as of 09:53, 5 August 2014
, 09:53, 5 August 2014no edit summary
Line 23:
Line 23:
fd = open_a_file(fd->file);
fd = open_a_file(fd->file);
dup2(fd, fd->tgt_fd);
dup2(fd, fd->tgt_fd);
+ close(fd);
+</pre>
+
+Now let's remember, that a file can be opened multiple times in one task, this is happens when you e.g. start a shell. One of the <code>/dev/tty</code> or alike files will sit under 0, 1 and 2 descriptors. Not a big deal, we just expand the <code>struct fd</code>
+
+<pre>
+ struct fd {
+ struct file *file;
+ int n_fds;
+ int *tgt_fds;
+ } *fd;
+</pre>
+
+and the code itself:
+
+<pre>
+ int fd, i;
+
+ fd = open_a_file(fd->file);
+ for (i = 0; i < fd->n_fds; i++)
+ dup2(fd, fd->tgt_fds[i]);
close(fd);
close(fd);
</pre>
</pre>
[[Category:Under the hood]]
[[Category:Under the hood]]