#!/bin/bash
# grp.sh: Rudimentary reimplementation of grep.

E_BADARGS=85

if [ -z "$1" ]    # Check for argument to script.
then
  echo "Usage: `basename $0` pattern"
  exit $E_BADARGS
fi  

echo

for file in *     # Traverse all files in $PWD.
do
  output=$(sed -n /"$1"/p $file)  # Command substitution.

  if [ ! -z "$output" ]           # What happens if "$output" is not quoted?
  then
    echo -n "$file: "
    echo "$output"
  fi              #  sed -ne "/$1/s|^|${file}: |p"  is equivalent to above.

  echo
done  

echo

exit 0

# Exercises:
# ---------
# 1) Add newlines to output, if more than one match in any given file.
# 2) Add features.