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Hello,</div>
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I am trying to use fts to traverse through the current directory without recursion and i either get a segfault of the following error when I call fts_children()</div>
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<br>
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fts_children: Undefined error: 0.</div>
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<br>
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Here's my code snippet below:<br>
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main</div>
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{</div>
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if(argc == 1)</div>
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PrintFileNames(".");</div>
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}<br>
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<span>void PrintFileNames(char* dir )<br>
</span>
<div>{<br>
</div>
<div><br>
</div>
<div> FTS *filetree = NULL;<br>
</div>
<div> FTSENT *file = NULL;<br>
</div>
<div> FTSENT *child = NULL;<br>
</div>
<div> char *path[] = {dir, NULL};<br>
</div>
<div><br>
</div>
<div> filetree = fts_open(path, FTS_PHYSICAL, &compare);<br>
</div>
<div><br>
</div>
<div> if(filetree == NULL)<br>
</div>
<div> ErrorMessage("fts_open failed");<br>
</div>
<div><br>
</div>
<div> else<br>
</div>
<div> {<br>
</div>
<div><br>
</div>
<div> while((file = fts_read(filetree)) != NULL)<br>
</div>
<div> {<br>
</div>
<div><br>
</div>
<div> child = fts_children(filetree, 0);<br>
</div>
<div><br>
</div>
<div> if(child == NULL)<br>
</div>
<div> ErrorMessage("fts_children");<br>
</div>
<div><br>
</div>
<div> printf("%s\n",child->fts_name);<br>
</div>
<div><br>
</div>
<div> }<br>
</div>
<div> }<br>
</div>
<div><br>
</div>
<div> if(errno != 0)<br>
</div>
<div> ErrorMessage("fts_read failed");<br>
</div>
<div><br>
</div>
<div> if( fts_close(filetree) < 0)<br>
</div>
<div> ErrorMessage("fts_close");<br>
</div>
<span></span></div>
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}</div>
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Can anyone shed some light on what's going on?</div>
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Thanks.<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> cs631apue-bounces@lists.stevens.edu <cs631apue-bounces@lists.stevens.edu> on behalf of Jan Schaumann <jschauma@stevens.edu><br>
<b>Sent:</b> Sunday, October 6, 2019 4:35 PM<br>
<b>To:</b> cs631apue@lists.stevens.edu <cs631apue@lists.stevens.edu><br>
<b>Subject:</b> Re: [cs631apue] About FTS</font>
<div> </div>
</div>
<div class="BodyFragment"><font size="2"><span style="font-size:11pt;">
<div class="PlainText">Yuxi Wang <ywang286@stevens.edu> wrote:<br>
<br>
> 1.To use these fields to reference any files represented by<br>
> other FTSENT structures will require that the path buffer be modified<br>
> using the information contained in that FTSENT structure's fts_pathlen<br>
> field. Any such modifications should be undone before further calls to<br>
> fts_read() are attempted. The fts_name field is always NUL-terminated.<br>
<br>
I'm honestly struggling to come up with a useful<br>
example, but the point is that you cannot manipulate<br>
the buffers (e.g., via strcat(3) etc.) in e.g., your<br>
comparison function, nor can you rely on the buffer to<br>
be NULL terminated for a previously returned element.<br>
<br>
That means that you can't keep a pointer to the<br>
element returned and subsequently call e.g. strlen(3)<br>
on _that_ element's fts_path field.<br>
<br>
Let's say you want to write a program that will print<br>
the path within the parent directory:<br>
<br>
$ pwd<br>
/tmp<br>
$ ls<br>
file<br>
$ printParentPath file<br>
tmp/file<br>
$ printParentPath /var/tmp/subdir/file<br>
subdir/file<br>
<br>
This might require you to keep track of the parent<br>
struct. You might try to<br>
<br>
- get strlen of current entry accpath, n<br>
- get strlen of parent entry accpath, m<br>
- malloc a buffer of size n + 1 + m<br>
- sprintf parent, '/', current to buffer<br>
<br>
But the parent entry's accpath may not be<br>
NULL-terminated, thus strlen(3) giving you a bogus<br>
result.<br>
<br>
> 2.What does the fts_accpath represent for? I tracked<br>
> the FTS structure and found it always equal<br>
> fts_name.<br>
<br>
fts_accpath will be different depending on whether<br>
you've specified FTS_NOCHDIR or not. With<br>
FTS_NOCHDIR, fts_accpath will look like fts_path,<br>
without, fts_accpath will look like fts_name.<br>
<br>
I haven't verified, but I could imagine that results<br>
will also differ based on whether you're following<br>
symlinks and the hierarchy includes symlinks to<br>
directories whereby directory traversal may encounter<br>
the same subdir via multiple paths.<br>
<br>
-Jan<br>
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