help learning bash

genisis300 · 2010-05-07 11:01:56

Hi All,

i've been trying to help out with the Archbang Project and come up with this little script only problem is it doesn't work as inteneded.
What i'm trying to-do is make sure the script can access the files it needs where ever it's run from .

#!/bin/bash
        if [ "$1" = "clean" ]; then
        echo $(pwd)
        rm -v $(pwd)/../overlay/src/pkgs/*.tar.*
        exit 1
        fi

        exec < $(pwd)/../overlay/src/pkgs/packages.extra
        while read package    
        do
        pkgs=$(echo "$pkgs $package")
        done

        echo "fetching $pkgs"
        pacman -d -Sw --noconfirm --cachedir $(pwd)/../overlay/src/pkgs $pkgs

i know about pwd and $0 for getting paths but wasn't sure the best way round making sure the script can find the files.

Anyone got any suggestions or links to some helpfull material i have done a google search but wasn't quiet sure how to word what i was doing.

Regards
Matthew

falconindy · 2010-05-07 11:31:48

http://tldp.org/LDP/abs/html/
http://mywiki.wooledge.org/BashFAQ

I can recommend that the central while/read loop be rewritten as:

IFS=$'\n' read -r -d $'\0' -a pkgs < "$PWD/../overlay/src/pkgs/packages.extra"

This leaves you with an array, so you'll then need to change the pacman execution slightly to:

pacman -Sdw --noconfirm --cachedir "$PWD/../overlay/src/pkgs" "${pkgs[@]}"

Relative paths is probably a bad idea. If you have a way to confirm at some point that a relative path is pointing to a correct location, save that. In other words, suppose at some point you're sure that the path "$PWD/../overlay/src" is known good. Save that as, for example, $absrcroot and then you can reference $absrcroot/pkgs instead of banking on your working directory not changing.

Also, as a general rule of thumb for variables: always double quote them unless you're without a doubt absolutely sure that no white space could ever exist in them. If you're not sure, quote it.

Last edited by falconindy (2010-05-07 11:33:50)

genisis300 · 2010-05-07 13:24:29

thank you i will try that shortly

Learning something new today

genisis300 · 2010-05-07 16:42:45

kk just so i understand this i had an idea of checking the out of $0 and PWD to work out where the script is
one of the 2 will have to contain the path to the script and therfore the project.

very crude but something like

if len $0 <1 then 
   check and use PWD instead

is that kinda what you where getting at?

Regards
Matthew

Last edited by genisis300 (2010-05-07 16:43:34)

Arch Linux

#1 2010-05-07 11:01:56

help learning bash

#2 2010-05-07 11:31:48

Re: help learning bash

#3 2010-05-07 13:24:29

Re: help learning bash

#4 2010-05-07 16:42:45

Re: help learning bash

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