Re: bash: relative to absolute path

From: Shea Martin (smartin_at_arcis.com)
Date: 01/11/05 

Date: Mon, 10 Jan 2005 19:53:56 -0700

Pascal Bourguignon wrote:
> Shea Martin <smartin@arcis.com> writes:
>
>
>>I often need to get the absolute path of a file in my bash scripts.
>>I started to device a path parser, but then found this cheezy but
>>simple solution. Does anyone have a more efficient/better solution?
>>[...]
>> DIR=$(cd "$DIR" && pwd && cd $OLDPWD)
>>[...]
>
>
> You don't need to go back to the old directory since $(...) forks a
> sub-shell that cannot change the working directory of the parent shell.
>
> DIR=$(cd "$DIR" && pwd)
Thanks, I should have known that.

>
> Given that a file may not have a _unique_ absolute path, this is as
> good as any other method to find an absolute path for a file. I don't
> think you can get any better.
>
>

I just realized that my current implementation will only work on existing files.
  here is one that is more flexible, though maybe not as simple or efficient.

~S

<code>
rel2abs()
{
    # make sure file is specified
    if [ -z "$1" ]
    then
       echo "$0 <path>"
       return 1
    fi

    # already absolute case
    if [ "${1:0:1}" = "/" ] || [ "$PWD" = "/" ]
    then
       ABS=""
    else
       ABS="$PWD"
    fi

    # loop thru path
    IFS="/"
    for DIR in $1
    do
       if [ -n "$DIR" ]
       then
          if [ "$DIR" = ".." ]
          then
             ABS="${ABS%/*}"

          elif [ "$DIR" != "." ]
          then
             ABS="$ABS/$DIR"

          fi
       fi
    done
    IFS=":"

    echo $ABS
    return 0
}
</code>