topic Re: PATH value in a variable in Operating System - Linux

PATH value in a variable

Jose Mosquera — Fri, 28 Jul 2006 07:03:19 GMT

Hi pals,

Please look this simple script content:
MAIN_PATH=/usr/local/bin
SUPPLEMENTARY_PATH=../..
FULL_PATH=$MAIN_PATH/$SUPPLEMENTARY_PATH
echo $FULL_PATH

/usr/local/bin/../..

How can I obtain (on-the-fly) the real/final path info content into $FULL_PATH? In this case must be "/usr".

Please omit the possibility to move to $FULL_PATH and to obtain the value of $PWD, I need to know the real/final content before moving.

For those that have a solution, please think that it would happen in this deliberate erroneous case of variable definition:
SUPPLEMENTARY_PATH=../../../../../..

Rgds.

Re: PATH value in a variable

Pete Randall — Fri, 28 Jul 2006 07:07:53 GMT

I'm not sure what you're really asking here but your syntax is wrong for a path. It should be

FULL_PATH=$MAIN_PATH:$SUPPLEMENTARY_PATH

Pete

Re: PATH value in a variable

Jose Mosquera — Fri, 28 Jul 2006 07:17:37 GMT

Pete,

You are wrong. The final PATH must be:
FULL_PATH=$MAIN_PATH/$SUPPLEMENTARY_PATH

Rgds.

Re: PATH value in a variable

Jonathan Fife — Fri, 28 Jul 2006 07:19:57 GMT

If you can access the MAIN_PATH and SUPPLEMENTARY_PATH variables directly, I'd do some sort of loop counting the number of '..'s in SUPPLEMENTARY_PATH and using the 'dirname' command to remove directories from MAIN_PATH. Something like:

MAINPATH=/usr/local/bin
SUPPPATH=../..

while [ $(echo $SUPPPATH | grep -c "\.\.") -gt 0 ]; do
SUPPPATH=$(dirname $SUPPPATH)
MAINPATH=$(dirname $MAINPATH)
done

echo $MAINPATH

There's probably an elegant perl script that will do the same...

Re: PATH value in a variable

Peter Nikitka — Fri, 28 Jul 2006 07:54:16 GMT

Hi,

try with perl:

perl -e 'use Cwd 'abs_path'; print abs_path($ARGV[0]) . "\n";' PATHNAME

mfG Peter

Re: PATH value in a variable

Peter Nikitka — Fri, 28 Jul 2006 08:00:18 GMT

Ups,

though functional, I recommend stripping some quotes:

perl -e 'use Cwd abs_path; print abs_path($ARGV[0]) . "\n";' PATHNAME

Sorry.

Additionally, here is a awk-function that did this as well, if I remember correctly:

awk 'function pathexp (name) { numdir=split(name,p,"/")
ndir_new=0
for(i=1;i<=numdir;i++) {
if(p[i]==".") continue
if(p[i]=="..") {if(ndir_new) {ndir_new--;continue}}
np[++ndir_new]=p[i]
}
if(!ndir_new) return(name)
new_name=np[1]
for(i=2;i<=ndir_new;i++) new_name=new_name"/"np[i]
return(new_name)
}
{print pathexp($1)}'

This expects your pathname at stdin.

mfG Peter

Re: PATH value in a variable

Enrico P. — Fri, 28 Jul 2006 08:22:06 GMT

Hi,
you can set your FULL_PATH variable:

FULL_PATH=`cd $MAIN_PATH/;cd $SUPPLEMENTARY_PATH;pwd`

Enrico