install_R_deps.sh

#!/bin/bash

echo "i <- rownames(installed.packages())" > __tmp__.R

grep -oh --include=\*.{Rmd,R} -r * -e "\(library\|require\)([A-Za-z0-9.]\+)" | \
    sed 's_library(_"_'  | \
    sed 's_require(_"_'  | \
    sed 's_)_",_'        | sort | uniq | \
    perl -p -e 's/\n/ /' | \
    sed 's_^_new <- c(_' | \
    sed  's_, *$_)_' \
         >> __tmp__.R

echo >> __tmp__.R
echo "install.packages(new[!new %in% i])" >> __tmp__.R

# For debugging
#cat __tmp__.R

R --quiet -e "source('__tmp__.R')"

rm __tmp__.R

Some updates: Fix to missing newline (L14); reduce length of input string (L8).