Symlinking shared libraries from a platform-specific directory

Question

We have a setup script for setting up a development environment, and setting up the image libraries is getting a bit messy:

# this is to get PNG and JPEG support working in PIL on Ubuntu
if [ -d /usr/lib/x86_64-linux-gnu ] ; then # 64 bit ubuntu
 sudo ln -s /usr/lib/x86_64-linux-gnu/libfreetype.so /usr/lib/
 sudo ln -s /usr/lib/x86_64-linux-gnu/libz.so /usr/lib/
 sudo ln -s /usr/lib/x86_64-linux-gnu/libjpeg.so /usr/lib/
fi
if [ -d /usr/lib/i386-linux-gnu/ ] ; then # 32 bit ubuntu
 sudo ln -s /usr/lib/i386-linux-gnu/libfreetype.so /usr/lib/
 sudo ln -s /usr/lib/i386-linux-gnu/libz.so /usr/lib/
 sudo ln -s /usr/lib/i386-linux-gnu/libjpeg.so /usr/lib/
fi
if [ -d /usr/lib64/ ] ; then # Redhat
 sudo ln -s /usr/lib64/libjpeg.so /usr/lib/
 sudo ln -s /usr/lib64/libz.so /usr/lib/
 sudo ln -s /usr/lib64/libfreetype.so /usr/lib/
fi

Answer 1

I'm not quite sure if your script should consist of elifs instead of ifs. I'm going to assume that it should be elifs since you don't want to be overwriting your links. If not just remove break or reverse the order of the directories.

for dir in /usr/lib{/x86_64-linux-gnu,/i386-linux-gnu,64}; do
 if [[ -d $dir ]]; then
 sudo ln -s $dir/{libfreetype,libz,libjpeg}.so /usr/lib
 break
 fi
done

Answer 2

Seems like you can do the if statement to set a variable to the first part of the path, then put all the file copies at the end after that.

(Warning: My bash is kind of bad. Haven't used it for a while. I think this is how it's done though... Might need quotes around the libpath assignments?)

# this is to get PNG and JPEG support working in PIL on Ubuntu
if [ -d /usr/lib/x86_64-linux-gnu ] ; then # 64 bit ubuntu
 libpath=/usr/lib/x86_64-linux-gnu
fi
if [ -d /usr/lib/i386-linux-gnu/ ] ; then # 32 bit ubuntu
 libpath=/usr/lib/i386-linux-gnu
fi
if [ -d /usr/lib64/ ] ; then # Redhat
 libpath=/usr/lib64
fi
sudo ln -s $libpath/libfreetype.so /usr/lib/
sudo ln -s $libpath/libz.so /usr/lib/
sudo ln -s $libpath/libjpeg.so /usr/lib/

• Paul: This looks good, you can use elif for the last two if statements as only 1 option should be chosen.

Answer 3

In the interests of dryness, and invoking as small number of commands as possible.

for dir in /usr/lib{/x86_64-linux-gnu,/i386-linux-gnu,64}; do
 [ -d $dir ] && echo $dir
done | {read dir;
for lib in {libfreetype,libz,libjpeg}.so; do
 echo ln -s $dir/$lib /usr/lib/
done} | sudo bash