Re: stat(1) print formats

[Assaf Gordon]

Hello David,

On 11/21/2014 01:33 PM, Pádraig Brady wrote:
> On 21/11/14 17:24, David Braun wrote:
> > 1. The use of left and right quotes is counter to tradition and complicates
> > any shell post processing of the output. All shells that I'm familiar with
> > use paired quotes (left, right or double). Mixing them become difficult to
> > deal with.
>
> That's been changed for quite a while with:
> http://git.sv.gnu.org/gitweb/?p=gnulib.git;a=commitdiff;h=1a43a98
>
> > 2. The use of quotes only occurs for the %N format and is only necessary
> > because of the "xxx -> yyy" result because of the possibility of special
> > characters in either of the xxx or yyy portions.

Perhaps an example of using C locale can help, also with shell-parsing.

    # Create a file and a symlink, with problematic characters
    $ touch "hello' wor"$'\n'ld
    $ ln -s hello* "hi' -> 'there"

    $ ls -log
    total 0
    -rw-rw-r-- 1  0 Nov 21 13:42 hello' wor?ld
    lrwxrwxrwx 1 13 Nov 21 13:42 hi' -> 'there -> hello' wor?ld


    # Using the default locale (in my case en_US.UTF-8)
    # Parsing will be challenging...
    $ stat -c %N h*
    ‘hello' wor\nld’
    ‘hi' -> 'there’ -> ‘hello' wor\nld’

    # Forcing C locale, the quotes are always single quotes,
    # and any quotes in the filenames are escaped:
    $ LC_ALL=C stat -c %N h*
    'hello\' wor\nld'
    'hi\' -> \'there' -> 'hello\' wor\nld'

Because the " -> " string is hard-coded in 'stat.c',
we can use it to split the string into src/dst filenames.
using the following shell commands:

    A=$(LC_ALL=C stat -c %N hi*)
    SRC=$(echo "$A" | sed "s/^'\(.*\)' -> '.*'$/\1/")
    DST=$(echo "$A" | sed "s/^'.*' -> '\(.*\)'$/\1/")
    echo "SRC ==$SRC=="
    echo "DST ==$DST=="

Will print:

    SRC ==hi\' -> \'there==
    DST ==hello\' wor\nld==

Though I wouldn't necessarily recommend using this in a production script - "find" + 
"-print0" is probably more robust.

HTH,
 - Assaf