Bash function to detect if an R command uses an external connection of anykind. Designed to be used with R CMD check

has_external_connection.sh

#!/bin/bash
# Bash function to detect if an R command uses an external connection of
# any kind.  Designed to be used with R CMD check

function has_external_connection {
  DIR=$(mktemp -d)

  # Use a local repository so we don't have to make an external connection for
  # `available.packages()`
  mkdir -p $DIR/src/contrib
  wget -q -O $DIR/src/contrib/PACKAGES 'https://cran.rstudio.com/src/contrib/PACKAGES'
  RPROFILE=$DIR/RProfile
  echo "options(repos = c(CRAN='file://$DIR'))" > $RPROFILE

  # Write trace results to outfile
  OUTFILE=$(tempfile -d $DIR)

  # Run the command using strace and trace only network system calls
  strace -E R_PROFILE_USER=$RPROFILE -f -qq -o $OUTFILE -e trace=network "$@"

  # Filter out
  # 1. child process start and exit signals
  # 2. local socket connections
  # 3. Connection continuation lines
  grep -q -E -v \
    -e "^[0-9]+ +[+-]{3}" \
    -e "[AP]F_LOCAL" \
    -e "^[0-9]+ +<\.\.\. connect resumed" \
    $OUTFILE

  return $?
}