strace-deps

#!/bin/bash

if [[ $# -lt 2 ]]; then
  echo "Usage: $0 <depfile> <command...>" >&2
  exit 1
fi

# The .d file we're going to write.
DEPSFILE=$1
shift

# The temporary file that holds strace output.
STRACEFILE=$DEPSFILE.$$.strace

# Remove the temp file when we're done.
function cleanup {
  rm -f "${STRACEFILE}"
}
trap cleanup EXIT

# strace the command and keep track of openat calls.
strace -o "${STRACEFILE}" -f -qq -y -e openat "$@"

# Function to de-dupe files and remove ones to ignore.
filterfiles() {
  # This may require tweaking if for example the directory you build
  # in is under /usr/.
  sort | uniq | grep -E -v '^(/etc/|/var/|/proc/|/lib/|/usr/|/tmp/)'
}

# Files that were written by this command.
OUTPUTS=$(gawk 'match($0, /O_WRONLY.* = [0-9]+<(.+)>$/, arr) { print arr[1]; }' "${STRACEFILE}" | filterfiles | xargs echo)
# Files that were read by this command.
INPUTS=$(gawk 'match($0, /O_RDONLY.* = [0-9]+<(.+)>$/, arr) { print arr[1]; }' "${STRACEFILE}" | filterfiles | xargs echo)

# Generate the deps file.
echo "${OUTPUTS}: ${INPUTS}" > "${DEPSFILE}"