# -*- sh -*-

# hello world
# print a simple string on stdout
echo Hello World

# argv
# access command line parameters (no segmentation fault accepted, nor silent exception, so some languages must explicitly check the presence of the argument)
echo $1

# env
# access environment variable
echo $HOME

# test file exists
# return exit code error (non zero) if a file does not exist
[ -e /etc/mtab ]

# test file readable
# return exit code error (non zero) if a file is not readable
[ -r /etc/mtab ]

# formatting
# print integers in a simple formatted string
a=1; b=2; echo "$a + $b = $[$a + $b]"

# system
# call an external program and check the return value
false || echo "false failed" 1>&2; echo done

# sed in place
# remove #-comments from a file (modifying the file, i.e. in place)
sed -i -e "s/#.*//" $1

# compile what must be
# find and compile .c files into .o when the .o is old or absent
for c in `find -name "*.c"`; do
  o=`echo $c | sed 's/.c$/.o/'`
  if [ "$c" -nt "$o" ]; then
    echo "compiling $c to $o"
    gcc -c -o "$o" "$c"
  fi
done


# grep
# grep with -F -i -h handling, usage, grep'ing many files
opts=''
while [ -n "$1" ]; do
    case $1 in
        -i) opts="-i $opts" ;;
        -F) opts="-F $opts" ;;
        -h) h=1 ;;
        *) break ;;
    esac
    shift
done

if [ $# = 0 ] || [ -n "$h" ]; then
    echo "usage: grep [-F] [-i] regexp [files...]"
    exit 1
fi

r=$1
shift

grep $opts $r "$@"