build/cat.sh

#!/bin/sh
# Copyright 2018 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# cat.sh output_file [file, ...]
# cat.sh concatenates all file arguments into output_file, separated by lines.
# cat.sh elides empty lines (in order to avoid breaking the symbolizer)

# Note: `cat $output $@` is not equivalent - that does not produce new lines
# between inputs.

readonly output="$1"

if [[ -z "$output" ]]; then
  echo output file not specified 1>&2
  exit 1
fi

shift 1

tmpfile=$( mktemp "${output}.XXXXXXXXXX" )
trap 'rm -f "${tmpfile}"' EXIT

for file in "$@"
do
  if [ ! -e "$file" ]; then
    echo "File does not exist: $file" 1>&2
    exit 1
  fi

  while read line
  do
    if [ -n "${line}" ]; then
      echo "${line}"
    fi
  done < "${file}"
done > "${tmpfile}"

mv "${tmpfile}" "${output}"