Hi, On Sat, Nov 12, 2011 at 11:45:56AM -0700, Eric Blake wrote: [...] > http://docs.python.org/library/os.path.html > >> os.path.relpath(path[, start]) > >> > >> Return a relative filepath to path either from the current directory > >> or from an optional start point. > > Ah, so the idea is that python has a function that computes a relative > pathname to one path given a starting point: > > $ relpath /usr/bin /tmp > ../usr/bin > $ relpath /usr/bin /usr/share > ../bin
Btw, there is an utility in freebsd ports called relpath: http://www.freebsd.org/cgi/cvsweb.cgi/ports/sysutils/relpath/ ftp://ftp.freebsd.org/pub/FreeBSD/ports/local-distfiles/beech/relpath-0.1.0.tar.gz $ lftp -c 'cat http://www.freebsd.org/cgi/cvsweb.cgi/~checkout~/ports/sysutils/relpath/pkg-descr' Usage: relpath [-d DIR] START_DIR END_PATH Find a relative path from START_DIR to END_PATH. Prints the relative path on standard out. If -d DIR, then only emit a relative path if both START_DIR and END_PATH are sub-directories of DIR; otherwise, emit an absolute path to END_PATH. > This seems like you could do it in shell without resorting to python, by > computing a canonical name for both the destination and the starting > point, then comparing common prefixes, and for every directory component > that differs after the common prefix, replacing the directory with > '../'. This has been done before; for example, this is from gnulib-tool: > > # func_relativize DIR1 DIR2 > # computes a relative pathname RELDIR such that DIR1/RELDIR = DIR2. > # Input: > # - DIR1 relative pathname, relative to the current directory > # - DIR2 relative pathname, relative to the current directory > # Output: > # - reldir relative pathname of DIR2, relative to DIR1 > func_relativize () > { > dir0=`pwd` > dir1="$1" > dir2="$2" > sed_first='s,^\([^/]*\)/.*$,\1,' > sed_rest='s,^[^/]*/*,,' > sed_last='s,^.*/\([^/]*\)$,\1,' > sed_butlast='s,/*[^/]*$,,' > while test -n "$dir1"; do > first=`echo "$dir1" | sed -e "$sed_first"` > if test "$first" != "."; then > if test "$first" = ".."; then > dir2=`echo "$dir0" | sed -e "$sed_last"`/"$dir2" > dir0=`echo "$dir0" | sed -e "$sed_butlast"` > else > first2=`echo "$dir2" | sed -e "$sed_first"` > if test "$first2" = "$first"; then > dir2=`echo "$dir2" | sed -e "$sed_rest"` > else > dir2="../$dir2" > fi > dir0="$dir0"/"$first" > fi > fi > dir1=`echo "$dir1" | sed -e "$sed_rest"` > done > reldir="$dir2" > } > > Doing it in fewer processes seems possible with something like a single > awk script, although I haven't tried writing one; at any rate, awk would > be more portable than python for the same task. > > But yes, providing this as an alternative mode of coreutils' realpath > instead of scripting it in shell or awk seems like a useful addition - > would you care to submit a patch? AFAIR the coreutils' realpath is called readlink. ;) Would "readlink --relative" or something like this be a good choice? Or should it rather be a new utility? -- ldv
pgpzdEsINszo9.pgp
Description: PGP signature
