moosechips

Simplify your bash PATH management with pathmunge. The pathmunge will add a directory to the beginning of your PATH if it is missing from your PATH. This means that you can safely .source ~/.bashrc without ending up with duplicate folders in your path (which you would get if you had used export PATH=/add/this/dir:$PATH). It is also clearer what folders you are adding to your path. This goes in your ~/.bashrc:

pathmunge () {
        if ! echo $PATH | /bin/egrep -q "(^|:)$1($|:)" ; then
           if [ "$2" = "after" ] ; then
              PATH=$PATH:$1
           else
              PATH=$1:$PATH
           fi
        fi
}
 
pathmunge /usr/local/blah/bin
pathmunge ~/bin
export PATH
# now PATH is ~/bin:/usr/local/blah/bin:<old path>

As a bonus, you can use pathmunge /dir/to/add after to append the directory to the end of your path instead of the beginning.

Code from TDLP Bash Beginners Guide

General instructions to rebuild a Fedora source rpm.

Note: This example uses the vlc source rpm, but it doesn’t work on my Fedora 8 system because there are problems installing dependencies, but the general commands should work on other packages

1. Install build tools
   

   su -c 'yum install yum-utils rpmdevtools'

2. Download source package. Either use yumdownloader to download from an existing repository:
   

   yumdownloader --source vlc

   or download directly from a server

   wget -nd ftp://ftp.pbone.net/mirror/rpm.livna.org/fedora/development/SRPMS/\
   vlc-0.9.0-0.5.20080802git.lvn10.src.rpm

3. Install the source package. This will unpack the source into your /$HOME/rpmbuild directory.
   

   rpm -Uvh vlc-0.8.6i-1.lvn8.src.rpm

4. Install build dependencies for the source package
   

   su -c 'yum-builddep vlc-0.8.6i-1.lvn8.src.rpm'

5. Edit the spec file
   

   cd ~/rpmbuild/SPECS
   vim vlc.spec

6. Add the new source package
   

   cd ../SOURCES
   wget -nd http://download.videolan.org/pub/videolan/vlc/0.9.2/vlc-0.9.2.tar.bz2

7. Build the rpm
   

   cd ../SPECS
   rpmbuild -bb vlc.spec

8. Install the rpm
   

   cd ../RPMS/x86_64
   rpm -Uvh vlc-0.9.2.fc8.x86_64.rpm

References:
Building a kernel from the src rpm
Fedora rpm guide

# install deb build tools

sudo apt-get install build-essential fakeroot dpkg-dev devscripts

# download the source code

apt-get source package

# install other packages needed to build

sudo apt-get build-dep package
cd package

# update the version in the changelog

dch -i

# make any changes to the source
# e.g. vim debian/rules

# then build the new package

dpkg-buildpackage -rfakeroot -uc -b

#install the package

cd ..
sudo dpkg -i package.deb