[2019-02-28 15:43] Jonathan de Boyne Pollard
<j.deboynepollard-newsgro...@ntlworld.com>
> > What exactly is decoded? Where should I read about escaping rules?
> How it is different from plain `xargs'?
>
> You are suffering from the notoriously poor Linux documentation. (-:
Thank you. Wouderful. I believe it should find its way into upstream
distribution. Also, reference to fstab(5) and this particular paragraph
may be useful:
The second field (fs_file).
This field describes the mount point (target) for the filesysâ
tem. For swap partitions, this field should be specified as
`none'. If the name of the mount point contains spaces or tabs
these can be escaped as `\040' and '\011' respectively.
> The manuals for fstab on the BSDs explain that the fields are encoded ,
> so that they can contain whitespace characters, with strvis() and must
> be decoded with strunvis() when read. The BSD C library getfsent()
> function does this for one.
>
> It is pretty much undocumented, but roughly the same in fact holds true
> for Linux operating systems and their C libraries. It is not the vis
> encoding scheme, and is rather an encoding scheme that is peculiar to
> fstab. But the fields are encoded so that they can contain whitespace
> characters, and the getfsent() library function (or, actually, the
> getmntent() library function in the GNU C library) does this for one.
>
> If you read fstab with a program like awk, it will of course read and
> process the encoded forms. To actually get hold of the decoded forms,
> so that they can be passed as arguments to programs that do not expect
> them to be encoded, such as unmount in the example; one has to pass them
> through a decoder program. fstab-decode is simply such a decoder
> program. It runs all of its arguments through the decoder, and then
> execs the result.
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