On Wednesday, October 17, 2012 3:05:14 PM UTC+2, tom.gr...@gmail.com wrote:
> On Tuesday, October 16, 2012 12:33:19 PM UTC+2, tom.gr...@gmail.com wrote:
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>> I am using CD to determine whether a given path exists as a directory, and I was expecting the second case to fail just like the first one does, since there is no difference between them in my mind.
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> Thanks to all those who replied, but I am afraid you're not touching upon my question. I am sorry I have not made my point clearly enough.
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> 1) In a world where directories can be symbolically linked, it is not necessarily true that './bobo/...' is equal to '.', even when 'bobo' exists. Truncating away 'bobo/..' on the assumption that they are the same is arguably incorrect, but it is certainly confusing if it is done in some cases and not in others!
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> 2) In the regular Unix shells, 'ls -ld bobo/..' and 'ls -ld ./bobo/..' both fail, with the error message that the file or directory does not exist.
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> 3) FILE_TEST shows the same strange difference between 'bobo/..' and './bobo/..':
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> IDL> print, file_test('./bobo/..', /dir)
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> 1
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> IDL> print, file_test('bobo/..', /dir)
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> 0
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> It looks like I will have to do what I was hoping to avoid:
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> 1) given a path like 'foo/bar/baz/../quux/..', use file_test(x, /dir) on every sub-path x:
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> file_test('foo', /dir)
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> file_test('foo/bar', /dir)
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> file_test('foo/bar/baz', /dir)
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> file_test('foo/bar/baz/..', /dir)
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> file_test('foo/bar/baz/../quux', /dir)
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> file_test('foo/bar/baz/../quux/..', /dir)
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> If IDL cannot be relied upon to fail in the next step when one or more of these path components don't exist, then I must test every one of them.
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> 2) If all of these tests pass, then
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> cd 'foo/bar/baz/../quux/..', curr=old
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> cd, old, curr=pwd
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> 3) pwd is now the fully-qualified path to the directory indicated by 'foo/bar/baz/../quux/..'
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> Cheers,
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> Tom
Well, symbolic links solve some problems, and create some others :-)
Quick and unportable hack: you can get the real path by calling 'realpath' in your Linux C library:
IDL> in_path='foo/bar/baz/../quux/..'
IDL> out_path=string(replicate(32b, 1024))
IDL> x=call_external('/lib64/libc-2.11.3.so', 'realpath', in_path, out_path, /ul64_value, value=[1,1], /auto_glue)
(adjust it to your system.)
If in_path does not exist, x will be zero, otherwise out_path will contain the real path.
regards,
Lajos
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