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// Copyright 2014 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.
package com.google.devtools.build.lib.shell;
import java.util.List;
/**
* Utility functions for Bourne shell commands, including escaping and
* tokenizing.
*/
public abstract class ShellUtils {
private ShellUtils() {}
/**
* Characters that have no special meaning to the shell.
*/
private static final String SAFE_PUNCTUATION = "@%-_+:,./";
/**
* Quotes a word so that it can be used, without further quoting,
* as an argument (or part of an argument) in a shell command.
*/
public static String shellEscape(String word) {
int len = word.length();
if (len == 0) {
// Empty string is a special case: needs to be quoted to ensure that it gets
// treated as a separate argument.
return "''";
}
for (int ii = 0; ii < len; ii++) {
char c = word.charAt(ii);
// We do this positively so as to be sure we don't inadvertently forget
// any unsafe characters.
if (!Character.isLetterOrDigit(c) && SAFE_PUNCTUATION.indexOf(c) == -1) {
// replace() actually means "replace all".
return "'" + word.replace("'", "'\\''") + "'";
}
}
return word;
}
/**
* Given an argv array such as might be passed to execve(2), returns a string
* that can be copied and pasted into a Bourne shell for a similar effect.
*/
public static String prettyPrintArgv(List<String> argv) {
StringBuilder buf = new StringBuilder();
for (String arg: argv) {
if (buf.length() > 0) {
buf.append(' ');
}
buf.append(shellEscape(arg));
}
return buf.toString();
}
/**
* Thrown by tokenize method if there is an error
*/
public static class TokenizationException extends Exception {
TokenizationException(String message) {
super(message);
}
}
/**
* Populates the passed list of command-line options extracted from {@code
* optionString}, which is a string containing multiple options, delimited in
* a Bourne shell-like manner.
*
* @param options the list to be populated with tokens.
* @param optionString the string to be tokenized.
* @throws TokenizationException if there was an error (such as an
* unterminated quotation).
*/
public static void tokenize(List<String> options, String optionString)
throws TokenizationException {
// See test suite for examples.
//
// Note: backslash escapes the following character, except within a
// single-quoted region where it is literal.
StringBuilder token = new StringBuilder();
boolean forceToken = false;
char quotation = '\0'; // NUL, '\'' or '"'
for (int ii = 0, len = optionString.length(); ii < len; ii++) {
char c = optionString.charAt(ii);
if (quotation != '\0') { // in quotation
if (c == quotation) { // end of quotation
quotation = '\0';
} else if (c == '\\' && quotation == '"') { // backslash in "-quotation
if (++ii == len) {
throw new TokenizationException("backslash at end of string");
}
c = optionString.charAt(ii);
if (c != '\\' && c != '"') {
token.append('\\');
}
token.append(c);
} else { // regular char, in quotation
token.append(c);
}
} else { // not in quotation
if (c == '\'' || c == '"') { // begin single/double quotation
quotation = c;
forceToken = true;
} else if (c == ' ' || c == '\t') { // space, not quoted
if (forceToken || token.length() > 0) {
options.add(token.toString());
token = new StringBuilder();
forceToken = false;
}
} else if (c == '\\') { // backslash, not quoted
if (++ii == len) {
throw new TokenizationException("backslash at end of string");
}
token.append(optionString.charAt(ii));
} else { // regular char, not quoted
token.append(c);
}
}
}
if (quotation != '\0') {
throw new TokenizationException("unterminated quotation");
}
if (forceToken || token.length() > 0) {
options.add(token.toString());
}
}
}
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