grep 无法在此文件中找到文本

Question

我克隆了git一个项目的源代码，以前grep在整个项目中发现一个词，SchemaHandler. grep在这个奇怪的代码文件中找不到这个词：

https://github.com/yawlfoundation/yawl/blob/master/src/org/yawlfoundation/yawl/schema/YDataValidator.java

是的，我承认它不是标准的文本文件，但grep也可以在二进制文件中找到字符串。事实上，它能够在项目的两个 jar 文件中找到这个词。为什么这个文本失败了？

我使用的命令grep -R SchemaHandler .位于克隆项目的根目录中。

我用大号Ubuntu的18.0.4和grep3.1

Answer 1

它确实找到了。问题是该文件有一个回车符 ( \r)，这会导致终端隐藏文件名。为了说明我的意思，比较这两个命令：

printf "foobar\n"

和

printf "foo\rbar\n"

这是每个人应该打印的内容：

$ printf "foobar\n"
foobar
$ printf "foo\rbar\n"
bar

第二个命令仍在打印foo，但\r会导致终端返回到行首，因此它被覆盖。如果您使用，您可以看到它od：

$ printf "foo\rbar\n" | od -c
0000000   f   o   o  \r   b   a   r  \n
0000010

当你运行你的时候会发生类似的事情grep -R：

$ git clone https://github.com/yawlfoundation/yawl
$ cd yawl
$ grep -R  SchemaHandler . | grep YDataValidator
 }   }   return schema ;    .replaceAll("type=\"", "type=\"xs:"); xmlns:xs");pes, soonn) e;

乍一看，这个结果似乎很奇怪。怎么来，似乎不包含字符串YDataValidator的行正在由grep YDataValidator? 答案是\r。该行实际上来自YDataValidator.java文件，但文件名被\r. 如果你告诉grep只打印匹配的字符串和它周围的几个字符，你可以更清楚地看到这一点：

$ grep -PRo '.{10}SchemaHandler.{10}' . | grep YDataVal
 * @a/org/yawlfoundation/yawl/schema/YDataValidator.java:d using a SchemaHandler.
./src/org/yawlfoundation/yawl/schema/YDataValidator.java:  private SchemaHandler handler;
./src/org/yawlfoundation/yawl/schema/YDataValidator.java:ler = new SchemaHandler(schema);
./src/org/yawlfoundation/yawl/schema/YDataValidator.java:          SchemaHandler handler =
./src/org/yawlfoundation/yawl/schema/YDataValidator.java:      new SchemaHandler(DOMUtil.g

在这里，由于没有\r在10个字符的任何立即周围的5个实例SchemaHandler中YDataValidator.java，显示正确的名称。您的原始命令返回了整个文件（整个文件仅被分割为一行，\r在 Linux 中未定义换行符），因此您看到一长行由于\r.

您可以通过运行此验证：

$ grep SchemaHandler ./src/org/yawlfoundation/yawl/schema/YDataValidator.java 
}   }   return schema ;    .replaceAll("type=\"", "type=\"xs:"); xmlns:xs");pes, soonn) e;

然后将输出与将所有内容替换\r为换行符时得到的结果进行比较：

$ grep SchemaHandler ./src/org/yawlfoundation/yawl/schema/YDataValidator.java | tr '\r' '\n'
/*
 * Copyright (c) 2004-2012 The YAWL Foundation. All rights reserved.
 * The YAWL Foundation is a collaboration of individuals and
 * organisations who are committed to improving workflow technology.
 *
 * This file is part of YAWL. YAWL is free software: you can
 * redistribute it and/or modify it under the terms of the GNU Lesser
 * General Public License as published by the Free Software Foundation.
 *
 * YAWL is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
 * Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with YAWL. If not, see <http://www.gnu.org/licenses/>.
 */

package org.yawlfoundation.yawl.schema;

import org.jdom2.Element;
import org.yawlfoundation.yawl.elements.data.YVariable;
import org.yawlfoundation.yawl.exceptions.YDataValidationException;
import org.yawlfoundation.yawl.schema.internal.YInternalType;
import org.yawlfoundation.yawl.util.DOMUtil;
import org.yawlfoundation.yawl.util.JDOMUtil;
import org.yawlfoundation.yawl.util.StringUtil;

import javax.xml.XMLConstants;
import java.util.*;

/**
 * This class serves as a validation mechanism for the specification specific
 * schema and the instance data from either the net or a task. This is performed
 * by taking the data available at the various validation points and converting
 * it into conventional XML which is then validated using a SchemaHandler.
 *
 * @author Mike Fowler
 *         Date: 05-Jul-2006
 */
public class YDataValidator {

    // Object that performs the real validation on XML documents
    private SchemaHandler handler;

    /**
     * Constructs a new validator and handler. The
     * handler is not ready for use until validateSchema
     * has been called.
     * @param schema a W3C XML Schema
     */
    public YDataValidator(String schema) {
        this.handler = new SchemaHandler(schema);
    }

    /**
     * Compiles and determines the validity of the current schema
     * @return true if the schema compiled without error.
     */
    public boolean validateSchema() {
        return handler.compileSchema();
    }

    /**
     * Validates a single data variable
     *
     * @param variable to be validated
     * @param data XML representation of variable to be validated
     * @param source
     * @throws YDataValidationException if the data is not valid
     */
    public void validate(YVariable variable, Element data, String source)
            throws YDataValidationException {
        List<YVariable> vars = new ArrayList<YVariable>(1);
        vars.add(variable);
        validate(vars, data, source);
    }

    /**
     * Validates a collection of variables against the schema. This is achieved by
     * temporarily adding a schema element declaration for the data. This avoids
     * attempting to create a new schema containing only the relevant data types.
     *
     * @param vars variables to be validated
     * @param data XML representation fo the variables to be validated
     * @param source
     * @throws YDataValidationException if the data is not valid
     */
    public void validate(Collection vars, Element data, String source)
            throws YDataValidationException {
        try {
            String schema = ensurePrefixedSchema(handler.getSchema());
            org.w3c.dom.Document xsd = DOMUtil.getDocumentFromString(schema);
            String ns = XMLConstants.W3C_XML_SCHEMA_NS_URI;

            //need to determine the prefix for the schema namespace
            String prefix = ensureValidPrefix(xsd.lookupPrefix(ns));

            org.w3c.dom.Element element = xsd.createElementNS(ns, prefix + "element");
            element.setAttribute("name", data.getName());

            org.w3c.dom.Element complex = xsd.createElementNS(ns, prefix + "complexType");
            org.w3c.dom.Element sequence = xsd.createElementNS(ns, prefix + "sequence");

            ArrayList varList = new ArrayList(vars);
            Collections.sort(varList);               // sort on YParameter ordering value

            for (Object obj : varList) {
                YVariable var = (YVariable) obj;
                org.w3c.dom.Element child = xsd.createElementNS(ns, prefix + "element");
                child.setAttribute("name", var.getName());

                String type = var.getDataTypeName();
                if (XSDType.isBuiltInType(type)) {
                    type = prefix + type;
                }
                else if (YInternalType.isType(type)) {
                    type = prefix + type;
                    xsd.getDocumentElement().appendChild(DOMUtil.getDocumentFromString(
                            YInternalType.valueOf(type).getSchemaString()).getDocumentElement());
                }
                child.setAttribute("type", type);

                if (var.isOptional()) {
                    child.setAttribute("minOccurs", "0");
                }

                sequence.appendChild(child);
            }

            complex.appendChild(sequence);
            element.appendChild(complex);
            xsd.getDocumentElement().appendChild(element);

            SchemaHandler handler =
                          new SchemaHandler(DOMUtil.getXMLStringFragmentFromNode(xsd));

            if (! handler.compileSchema()) {
                throw new YDataValidationException(
                    handler.getSchema(),
                    data,
                    handler.getConcatenatedMessage(),
                    source,
                    "Problem with process model.  Failed to compile schema");
            }

            if (! handler.validate(JDOMUtil.elementToString(data))) {
                throw new YDataValidationException(
                    handler.getSchema(),
                    data,
                    handler.getConcatenatedMessage(),
                    source,
                    "Problem with process model.  Schema validation failed");
            }
        }
        catch (Exception e) {
            if (e instanceof YDataValidationException) throw (YDataValidationException) e;
        }
    }

    /**
     * @return String representation of the schema
     */
    public String getSchema() {
        return handler.getSchema();
    }

    /**
     * @return All error/warning messages relating to the last validation/compilation
     */
    public List<String> getMessages() {
        return handler.getMessages();
    }

    /**
     * @return the set of (first-level) type names defined in this schema
     */
    public Set<String> getPrimaryTypeNames() {
        return handler.getPrimaryTypeNames();
    }

    /**
     * Utility method to ensure the prefix is valid (enforces : and
     * defaults to xs:)
     *
     * @param prefix to validate
     * @return validated prefix
     */
    private String ensureValidPrefix(String prefix) {
        if (StringUtil.isNullOrEmpty(prefix)) {
            return "xs:";
        }
        else if (! prefix.endsWith(":")) {
            return prefix + ":";
        }
        return prefix;
    }


    /**
     * A schema may not have a valid prefix if a spec contains no complex types, so
     * this makes sure it gets one in that case
     * @param schema the schema string to check
     * @return a correctly (or defaultly) prefixed schema string
     */
    private String ensurePrefixedSchema(String schema) {
        if (!schema.contains(":schema")) {
            schema = schema.replaceFirst("schema xmlns", "schema xmlns:xs");
            schema = schema.replaceAll("<", "<xs:")
                           .replaceAll("<xs:/", "</xs:")
                           .replaceAll("type=\"", "type=\"xs:");
        }    
        return schema ;
    }
}

或者，您可以将输出通过管道传送到一个寻呼机less，它会显示\ras^M并且还可以帮助您识别您要查找的行。