Environment Variables
 

Environment Variables

Here is a typical variable declaration at the beginning of a SlackBuilds.org script:

PRGNAM=some_program_name
VERSION=1.0.0
ARCH=${ARCH:-i486}
BUILD=${BUILD:-1}
TAG=${TAG:-_SBo}

CWD=$(pwd)
TMP=${TMP:-/tmp/SBo}
PKG=$TMP/package-$PRGNAM
OUTPUT=${OUTPUT:-/tmp}

The syntax of ${TMP:-/tmp/SBo} means that if the $TMP variable exists in the parent environment then use that value otherwise assign the value of the variable to (in this case) /tmp/SBo.

Assigning a value to $TMP in one of several places is straightforward (~/.bashrc, /etc/bashrc, /etc/profile.d, etc.).

I would like to assign the OUTPUT variable to $CWD. Yet $CWD is unknown to the parent environment and unknown until I run the build script.

I can:

1. Manually edit the script to OUTPUT=$CWD.
2. Start the script with OUTPUT=$(pwd) sh buildscript

I would never remember option 2 all the time. Therefore I always edit build scripts with option 1. I've been doing that for a long time, but I wonder whether a more clever method exists so could run these scripts as is without manually editing.

Is there a way to programmatically assign OUTPUT globally so all I need do is change to the build directory and type sh buildscript?

You could create a simple script especially for executing slackbuilds with your environment settings (and based on the current directory at time of invocation).

Maybe alias will help you too. Add this to your ~/.bashrc:

Well, we're on the same page anyway. :) I too thought about a script, a function, and an alias.