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Re: [PATCH] fts: reduce two or more trailing spaces to just one, usually


From: Jim Meyering
Subject: Re: [PATCH] fts: reduce two or more trailing spaces to just one, usually
Date: Tue, 04 Sep 2012 13:09:24 +0200

Eric Blake wrote:
> On 09/04/2012 04:57 AM, Eric Blake wrote:
>>> * lib/fts.c (fts_open): Upon initialization, if a name ends in two
>>> or more slashes, trim all but the final one.  But if a name consists
>>> solely of two or more slashes, reduce it to "//", not to "/".
>>>
>>
>> For two slashes, that is correct.  But trimming "///" to "//" is a
>> violation of POSIX and fails on cygwin; "///" must be the same as "/",
>> not "///".
>>
>>> +++ b/lib/fts.c
>>> @@ -487,6 +487,14 @@ fts_open (char * const *argv,
>>>          for (root = NULL, nitems = 0; *argv != NULL; ++argv, ++nitems) {
>>>                  /* *Do* allow zero-length file names. */
>>>                  size_t len = strlen(*argv);
>>> +
>>> +                /* If there are two or more trailing slashes, trim all but 
>>> one,
>>> +                   but don't change "//" to "/".  */
>>> +                char const *v = *argv;
>>> +                if (2 < len && v[len - 1] == '/')
>>> +                  while (2 < len && v[len - 2] == '/')
>>> +                    --len;
>
> I think that this would do the right thing, though (notice that it
> strips all but 1 slash for anything longer than "//" to begin with):
>
> +                char const *v = *argv;
> +                if (2 < len && v[len - 1] == '/')
> +                  while (1 < len && v[len - 1] == '/')
> +                    --len;

Here's the revised commit:

>From 3a9002d3cc63da7110f133b1040d2d2b0aad8305 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Tue, 4 Sep 2012 11:36:38 +0200
Subject: [PATCH] fts: reduce two or more trailing slashes to just one,
 usually

* lib/fts.c (fts_open): Upon initialization, if a name ends in two
or more slashes, trim all but the final one.  But if a name consists
solely of two slashes, don't modify it.  If it consists solely of
three or more slashes, strip all but one.

This is part of the solution to a minor problem with rm:
it would print a bogus ELOOP diagnostic when failing to remove
the slash-decorated name of a symlink-to-directory:

    $ mkdir d && ln -s d s && env rm -r s/
    rm: cannot remove 's': Too many levels of symbolic links

With the change below and a trivial don't-trim-trailing-slashes
adjustment to remove.c, it does this:

    $ env rm -r s/
    rm: cannot remove 's/': Not a directory

Improved by: Eric Blake
---
 ChangeLog | 21 +++++++++++++++++++++
 lib/fts.c |  8 ++++++++
 2 files changed, 29 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index d4d2cb1..0874c81 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,26 @@
 2012-09-04  Jim Meyering  <address@hidden>

+       fts: reduce two or more trailing spaces to just one, usually
+       * lib/fts.c (fts_open): Upon initialization, if a name ends in two
+       or more slashes, trim all but the final one.  But if a name consists
+       solely of two slashes, don't modify it.  If it consists solely of
+       three or more slashes, strip all but one.
+
+       This is part of the solution to a minor problem with rm:
+       it would print a bogus ELOOP diagnostic when failing to remove
+       the slash-decorated name of a symlink-to-directory:
+
+           $ mkdir d && ln -s d s && env rm -r s/
+           rm: cannot remove 's': Too many levels of symbolic links
+
+       With the change below and a trivial don't-trim-trailing-slashes
+       adjustment to remove.c, it does this:
+
+           $ env rm -r s/
+           rm: cannot remove 's/': Not a directory
+
+       Improved by: Eric Blake
+
        fts: when there is no risk of overlap, use memcpy, not memmove
        * lib/fts.c (fts_alloc): Fix unjustified memcopy: s/memmove/memcpy/

diff --git a/lib/fts.c b/lib/fts.c
index ce14a80..36f7e0d 100644
--- a/lib/fts.c
+++ b/lib/fts.c
@@ -487,6 +487,14 @@ fts_open (char * const *argv,
         for (root = NULL, nitems = 0; *argv != NULL; ++argv, ++nitems) {
                 /* *Do* allow zero-length file names. */
                 size_t len = strlen(*argv);
+
+                /* If there are two or more trailing slashes, trim all but one,
+                   but don't change "//" to "/", and do map "///" to "/".  */
+                char const *v = *argv;
+                if (2 < len && v[len - 1] == '/')
+                  while (1 < len && v[len - 2] == '/')
+                    --len;
+
                 if ((p = fts_alloc(sp, *argv, len)) == NULL)
                         goto mem3;
                 p->fts_level = FTS_ROOTLEVEL;
--
1.7.12.176.g3fc0e4c



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