Implement read -n, and a placeholder for -r.

Addresses issue #26.

core/builtin.py

@@ -365,12 +365,32 @@ def Jobs(argv, job_state):
  return 0


READ_SPEC = _Register('read')
READ_SPEC.ShortFlag('-r')
READ_SPEC.ShortFlag('-n', args.Int)

def Read(argv, mem):
  # TODO:
  # - parse flags.
  # - Use IFS instead of Python's split().

  names = argv
  arg, i = READ_SPEC.Parse(argv)

  if not arg.r:
    util.warn('*** read without -r not implemented ***')

  names = argv[i:]
  if arg.n is not None:
    try:
      name = names[0]
    except IndexError:
      name = 'REPLY'  # default variable name
    s = os.read(sys.stdin.fileno(), arg.n)
    #log('read -n: %s = %s', name, s)

    state.SetLocalString(mem, name, s)
    # NOTE: Even if we don't get n bytes back, there is no error?
    return 0

  line = sys.stdin.readline()
  if not line:  # EOF
    return 1
@@ -387,11 +407,13 @@ def Read(argv, mem):

  strs = line.split(None, n-1)

  # TODO: Use REPLY variable here too?
  for i in xrange(n):
    try:
      s = strs[i]
    except IndexError:
      s = ''  # if there are too many variables
    #log('read: %s = %s', names[i], s)
    state.SetLocalString(mem, names[i], s)

  return status

gold/nix.sh

@@ -0,0 +1,32 @@
#!/bin/bash
#
# Usage:
#   ./nix.sh <function name>

set -o nounset
set -o pipefail
set -o errexit

# My simpler rewrite.
isElfSimple() {
  local path=$1  # double quotes never necessary on RHS
  local magic

  # read 4 bytes from $path, without escaping, into $magic var
  read -r -n 4 magic < "$path"

  # Return the exit code of [[
  [[ "$magic" =~ ELF ]]
}

isElfSimpleWithStdin() {
  seq 3 > /tmp/3.txt
  while read line; do
    echo $line
    isElfSimple /bin/true && echo YES
    isElfSimple $0 || echo NO
    echo
  done < /tmp/3.txt
}

"$@"

spec/builtins.test.sh

@@ -202,6 +202,18 @@ echo /$x/$y/$z/
umask | grep '[0-9]\+'  # check for digits
# status: 0

### Read -n (with $REPLY)
echo 12345 > $TMP/readn.txt
read -n 4 x < $TMP/readn.txt
read -n 2 < $TMP/readn.txt  # Do it again with no variable
argv.py $x $REPLY
# stdout: ['1234', '12']
# N-I dash stdout: []

### get umask
umask | grep '[0-9]\+'  # check for digits
# status: 0

### set umask in octal
rm $TMP/umask-one $TMP/umask-two
umask 0002

test/gold.sh

@@ -92,6 +92,10 @@ glob() {
  _compare gold/glob.sh
}

nix() {
  _compare gold/nix.sh isElfSimpleWithStdin
}

all() {
  version-text
  count