topic Expand a path passed to a script in Operating System - Linux

Expand a path passed to a script

Steve Tesch — Thu, 19 Jan 2006 14:47:27 GMT

I'm working in HP-UX 11.11 using the ksh shell. Does anyone know how I can expand a path that has been passed as a parameter to a script?

For example, if the current directory is "/database/app" and the user passes "../bin", I need to expand it to "/database/bin". Or if the current directory is "/database/app" and the user passes "../bin/myfile.txt" I need it to expand to "/database/bin/myfile.txt".

I've come up with a way to brute force the result but I have to believe there's an easier way. I've included my brute force method in an attachment.

Any help would be appreciated.

Re: Expand a path passed to a script

Victor Fridyev — Thu, 19 Jan 2006 14:55:10 GMT

Hi,

If you need to use expanded path in the script, use, if the path is the first parameter:
PATH=$PATH:$PWD/$1
If you want to expand path for your interactive shell, run

. script dirname

after the shell prompt.
The script should contain the same string

HTH

Re: Expand a path passed to a script

Ivan Ferreira — Thu, 19 Jan 2006 15:03:42 GMT

Hi Steve:

I don't understand whell what you need to do, because if are in /database/app and you use the ../bin or replace by /database/bin, you have the same results. I don't see the difference.

Re: Expand a path passed to a script

Steve Tesch — Thu, 19 Jan 2006 15:26:22 GMT

Victor,
Ivan,

Apparently my original explanation was not clear. When I stated that I need to be able to expand a path, I did not mean PATH, I was simply referring to any combination of typed directories the user may pass to a script, which is why I included examples.

As to the reason this is required; while you are correct that the examples I gave are equivalent within the shell, the relative paths have no meaning to another user viewing the results unless they know where the script was run from in the first place. This particular script can be run from anywhere on the system and the results have to indicate absolute paths in order to make any sense.

If that were the only issue, simply reporting the starting directory would reoslve the problem. However, absolute paths are a must when the results have to be sortable in a spreadsheet by path. Attempting to sort relative paths and make any sense of them is impossible.

I hope this helps clarify what I'm looking for.

Steve

Re: Expand a path passed to a script

Ivan Ferreira — Thu, 19 Jan 2006 15:47:14 GMT

What if you simply use:

APP_PATH=/database/app

Then, in your script, always use:

$APP_PATH/$1

So, if APP_PATH is /database/app, and the user passes ../bin, doest matter where he is, he will go to

/database/app/../bin -> /database/bin

Re: Expand a path passed to a script

James R. Ferguson — Thu, 19 Jan 2006 15:58:51 GMT

Hi Steve:

# cat getpath
#!/usr/bin/sh
pwd
echo ${1}
WHERE=`perl -le 'use Cwd qw(realpath);print realpath $ARGV[0];' $1`
echo ${WHERE}

For example:

# cd /var/tmp/dummydir && ./getpath ../bin
/var/tmp/dummydir
../bin
/var/tmp/bin

Does that help? This is based on the realpath() C library function.

Regards!

...JRF...

Re: Expand a path passed to a script

Steve Tesch — Thu, 19 Jan 2006 15:59:48 GMT

Victor,

Again, the issue isn't manipulating directories within the shell, it's being able to report the absolute path, even if the user specified a relative one.

The answer is straight-forward if the user actually passes a directory but if they pass a filename, it gets much trickier as you can see from the brute force method I uploaded.

Steve

Re: Expand a path passed to a script

Steve Tesch — Thu, 19 Jan 2006 16:05:31 GMT

James,

Your answer looks like it's on the right track but I get the following error when i attempt to run it:

Can't locate Cwd.pm in @INC (@INC contains: /opt/perl5/lib/5.00502/PA-RISC1.1 /opt/perl5/lib/5.00502 /opt/perl5/lib/site_perl/5.005/PA-RISC1.1 /opt/perl5/lib/site_perl/5.005 .) at -e line 1.
BEGIN failed--compilation aborted at -e line 1.

Any thoughts?

Steve

Re: Expand a path passed to a script

Leif Halvarsson_2 — Thu, 19 Jan 2006 16:08:27 GMT

Hi,
Just one simple idea.
Is the commands "basename" and "dirname" of any help ?

dirname return the directory part of a path and, basename the filename.

Re: Expand a path passed to a script

James R. Ferguson — Thu, 19 Jan 2006 16:11:31 GMT

Hi Steve:

It appears that the 'Cwd' module required isn't in your rather old version of perl.

You could download the module from CPAN:

http://search.cpan.org/~kwilliams/PathTools-3.15/Cwd.pm

...or better, yet, upgrade your version of perl:

http://h20293.www2.hp.com/portal/swdepot/displayProductInfo.do?productNumber=PERL

Regards!

...JRF...

Re: Expand a path passed to a script

Steve Tesch — Thu, 19 Jan 2006 16:16:37 GMT

First, my apologies, I addressed a previous reply to Victor when it should have been addressed to Ivan.

Leif - Thanks for the input but dirname and basename do not expand relative paths. They were one of my first attempts.

James - I appricate the quick response. I'll look into updating my perl and let you know how it turns out.

Thanks to all,

Steve

Re: Expand a path passed to a script

Ivan Ferreira — Thu, 19 Jan 2006 16:17:06 GMT

Still trying:

APP_PATH=/database/app
FULLPATH=`cd $APP_PATH/$1; pwd`
echo $FULLPATH

Re: Expand a path passed to a script

Ivan Ferreira — Thu, 19 Jan 2006 16:20:03 GMT

And going, and going...

APP_PATH=/var/adm/syslog
RELATIVE=`echo $1 |grep "^\."|wc -l`

# If the arg starts with dot, then is a relative path, else just use the specified path
if [ $RELATIVE -gt 1 ]; then
REALPATH=`cd $APP_PATH/$1;pwd`
fi

Re: Expand a path passed to a script

James R. Ferguson — Thu, 19 Jan 2006 16:21:09 GMT

Hi Steve:

The perl update is quick and simple and so, so worthwhile. Perl 5.8.x has incorporated lots of good things into its core.

Regards!

...JRF...

Re: Expand a path passed to a script

Steve Tesch — Thu, 19 Jan 2006 16:22:26 GMT

Ivan,

Your solution works if the user passes a directory, and is very similar to the method I uploaded. However if they are passing a filename, it gets an error.

I need a solution for both possibilities.

Thanks for the continued effort.

Steve

Re: Expand a path passed to a script

Ivan Ferreira — Thu, 19 Jan 2006 16:29:55 GMT

Sorry, I did not see your previous reply addressed to victor (me) about the file.

Re: Expand a path passed to a script

Steve Tesch — Thu, 19 Jan 2006 16:31:01 GMT

Ivan,

Your new solution works in most cases but not all. If you pass it a sub-directory of the current directory, it will return the current directory, instead of the full path to the sub-directory.

Your first solution did not have this problem. Also, this solution still can't handle a filename.

Thanks again,

Steve

Re: Expand a path passed to a script

Leif Halvarsson_2 — Thu, 19 Jan 2006 16:34:54 GMT

CUR=/abc/def
DIR=$(dirname ../xyz/abc.txt)
FILE=$(basename ../xyz/abc.txt)

cd $DIR
ABSOLUTE=$(pwd)

FULL_PATH=${ABSOLUTE}/${FILE}

it should work also with an absolute path or a filename only

Re: Expand a path passed to a script

Rodney Hills — Thu, 19 Jan 2006 16:36:22 GMT

You could compile the following c program that takes a path as its only argument and returns the real path. (Even compiles with the brain dead supplied cc compiler).

#include
main(argc,argv,envp)
int argc;
char *argv[],*envp[];
{
char realp[255];
(void)realpath(argv[1],realp);
printf("%s\n",realp);
exit(0);
}

HTH

-- Rod Hills

Re: Expand a path passed to a script

Steve Tesch — Thu, 19 Jan 2006 16:45:17 GMT

Leif,

Very close! However, if the user passes a path or filename that is already in absolute format (i.e. /home), your solution doubles the initial forward slash (i.e. //home). If they pass the root directory, it returns three forward slashes (i.e. ///).

Thanks for the effort,

Steve