Re: [PATCH] doc: note the relationship between realpath and readlink

[Dmitry V. Levin]

On Wed, Feb 08, 2017 at 09:04:38PM -0800, Pádraig Brady wrote:
> Now that `realpath` is widely available, recommend it
> over the less cross compatible `readlink -f`.

I'm not sure there is enough evidence to make this statement about
compatibility.  Wouldn't it be better to use a different rationale?

> * doc/coreutils.texi (realpath invocation): Mention why realpath
> is the preferred command for canonicalization.
> (readlink invocation): Recommend realpath for canonicalization.
> * man/readlink.x: Likewise.
> ---
>  doc/coreutils.texi | 9 ++++++++-
>  man/readlink.x     | 2 ++
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/coreutils.texi b/doc/coreutils.texi
> index 629136b..4935b80 100644
> --- a/doc/coreutils.texi
> +++ b/doc/coreutils.texi
> @@ -10260,7 +10260,8 @@ of a symbolic link, it produces no output and exits 
> with a nonzero exit code.
>  
>  @command{readlink} outputs the absolute name of the given files which contain
>  no @file{.}, @file{..} components nor any repeated separators
> -(@file{/}) or symbolic links.
> +(@file{/}) or symbolic links.  Note the @command{realpath} command is the
> +preferred command to use for canonicalization.  @xref{realpath invocation}
>  
>  @end table
>  
> @@ -13685,6 +13686,12 @@ all but the last component of the specified files 
> must exist.  Synopsis:
>  realpath [@var{option}]@dots{} @var{file}@dots{}
>  @end example
>  
> +The file name canonicalization functionality overlaps with that of the
> +@command{readlink} command, but this is the preferred command for

Why this contradicting "but"?

> +canonicalization as it's a more suitable command name, and its syntax
> +is more compatible across systems.  In addition this command supports
> +relative file name processing functionality.

Again, I'm not sure there is enough evidence to make this statement about
compatibility.  As realpath has all canonicalization functionality of
readlink plus some of its own, this should be enough to recommend realpath
over readlink for canonicalization.


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