shell.bzl

# Copyright 2017 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Skylib module containing shell utility functions."""

def _array_literal(iterable):
    """Creates a string from a sequence that can be used as a shell array.

    For example, `shell.array_literal(["a", "b", "c"])` would return the string
    `("a" "b" "c")`, which can be used in a shell script wherever an array
    literal is needed.

    Note that all elements in the array are quoted (using `shell.quote`) for
    safety, even if they do not need to be.

    Args:
      iterable: A sequence of elements. Elements that are not strings will be
          converted to strings first, by calling `str()`.

    Returns:
      A string that represents the sequence as a shell array; that is,
      parentheses containing the quoted elements.
    """
    return "(" + " ".join([_quote(str(i)) for i in iterable]) + ")"

def _quote(s):
    """Quotes the given string for use in a shell command.

    This function quotes the given string (in case it contains spaces or other
    shell metacharacters.)

    Args:
      s: The string to quote.

    Returns:
      A quoted version of the string that can be passed to a shell command.
    """
    return "'" + s.replace("'", "'\\''") + "'"

shell = struct(
    array_literal = _array_literal,
    quote = _quote,
)