Joerg Wunsch <aus...@uriah.heep.sax.de> wrote, on 18 Oct 2017:
>
> As Martijn Dekker wrote:
>
> > Is there a way, using POSIX shell and utilities, to reliably test if two
> > files are on the same file system?
>
> df -P appears to be required to have the filesystem name as the first
> column. Filesystem names with a space however might be a problem, at
> least if they contain a number after the space since that cannot be
> distinguished from the number of blocks.
After the filesystem name there are four numeric fields with a trailing '%'
on the fourth. Treating this as the terminator for the filesystem name
ought to be good enough in practice. It would only not work in the
extremely unlikely event that a filesystem name has within it four numeric
fields with a trailing '%' on the fourth, or if two different filesystem
names are the same when trailing blanks are removed.
I tried it with the following command and it seems to work:
df -P file1 file2 |
sed '1d;s/\([[:blank:]]\{1,\}[[:digit:]]\{1,\}\)\{4\}%[[:blank:]].*//'
--
Geoff Clare <g.cl...@opengroup.org>
The Open Group, Apex Plaza, Forbury Road, Reading, RG1 1AX, England
