Script to ensure ld.so.cache is usable and updated

check-ld-cache-good.sh

#!/bin/sh -e

# save the original LD_LIBRARY_PATH, and unset it to check the cache
ORIGINAL_LD_LIBRARY_PATH="$LD_LIBRARY_PATH"
LD_LIBRARY_PATH=""
export LD_LIBRARY_PATH

# FINAL_BINARY should be set and exported to what the "real" final executable 
# that's run is so we can check that
# an alternative would be to always run the "real" final executable immediately
# after this script in the chain, and then check "$1" here, but that is probably
# fragile
if [ -z "$FINAL_BINARY" ]; then
    echo "FINAL_BINARY unset, can't check the dynamic linker cache for correctness"
else
    # this is a bit tricky, we want to exit 0 if we didn't find a library, but
    # exit 1 if we didn't _not_ find a library, so use the output phrase
    # "=> not found" as what to look for from ldd
    # TODO: make this less of a hack?
    if ldd "$FINAL_BINARY" | grep "=> not found" | grep -q "=> not found"; then
        # regenerate the cache first
        LD_LIBRARY_PATH=$ORIGINAL_LD_LIBRARY_PATH
        export LD_LIBRARY_PATH
        "$SNAP/meta/hooks/install"
        # unset to continue executing the next command in the chain
        LD_LIBRARY_PATH=""
        export LD_LIBRARY_PATH
    fi
fi

# execute the next command in the chain
exec "$@"