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Java中执行Shell命令

Java执行Shell命令返回127

引言

在Java开发中,我们经常需要调用系统的Shell命令来完成一些特定的任务。然而,有时候执行Shell命令可能会返回一个特定的错误码,比如127。本文将介绍什么是Shell命令返回码,以及当Java执行Shell命令返回127时可能的原因和解决办法。

什么是Shell命令返回码?

Shell命令返回码是指Shell命令在执行完毕后返回给调用者的一个整数值。在Unix和类Unix系统中,执行成功的命令返回码通常是0,而非零的返回码表示执行失败或出现了某种错误。其中,特定的返回码可能有特定的含义,如127。

为什么Java执行Shell命令返回127?

当我们在Java中执行Shell命令时,Java会调用系统的Shell来执行命令,并获取其返回码。如果Java执行Shell命令返回127,那么可能有以下几个原因:

  1. 没有找到Shell可执行文件:当Java执行Shell命令时,会尝试在系统环境变量PATH所指定的路径中查找Shell可执行文件。如果没有找到Shell可执行文件,Java就无法执行命令并返回127。

  2. Shell命令无法执行:当Java执行Shell命令时,如果Shell命令本身无法执行或者不存在,Java将无法执行命令并返回127。这可能是因为Shell命令的路径错误、权限不足等原因导致的。

  3. Shell命令执行失败:当Java执行Shell命令时,如果Shell命令执行失败,比如命令语法错误、参数错误等,Shell会返回一个非零的错误码。如果返回的错误码正好是127,那么Java就会将该错误码作为执行Shell命令返回的结果。

如何解决Java执行Shell命令返回127的问题?

要解决Java执行Shell命令返回127的问题,我们可以采取以下几个步骤:

  1. 检查Shell可执行文件路径:首先,我们需要确保系统中正确配置了Shell可执行文件的路径。可以通过执行echo $PATH命令来查看系统环境变量PATH中是否包含了Shell可执行文件的路径。如果没有包含,可以通过修改环境变量配置文件或者手动添加路径来解决。

  2. 检查Shell命令是否可执行:其次,我们需要验证Shell命令本身是否可执行。可以尝试在命令行中直接执行Shell命令,看是否能够正常执行。如果无法执行,可能是Shell命令的路径错误或者权限不足导致的。可以尝试修改Shell命令的路径或者修改权限来解决。

  3. 检查Shell命令执行是否失败:最后,我们需要检查Shell命令的执行情况。可以通过捕获Java执行Shell命令时的异常来获取更多的错误信息。可以使用ProcessBuilder类来执行Shell命令,并通过调用Process对象的waitFor()方法来获取命令执行的返回码。如果返回的错误码为127,可以通过Process对象的getErrorStream()方法来获取错误信息,并进一步分析和解决问题。

下面是一个使用Java执行Shell命令的示例代码:

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;


public class ShellCommandExecutor {

public static void main(String[] args) {

try {

ProcessBuilder processBuilder = new ProcessBuilder("ls", "-l");

Process process = processBuilder.start();



        <span class="token class-name">BufferedReader</span> reader <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">BufferedReader</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">InputStreamReader</span><span class="token punctuation">(</span>process<span class="token punctuation">.</span><span class="token function">getInputStream</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token class-name">String</span> line<span class="token punctuation">;</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>line <span class="token operator">=</span> reader<span class="token punctuation">.</span><span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>line<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>

        <span class="token keyword">int</span> exitCode <span class="token operator">=</span> process<span class="token punctuation">.</span><span class="token function">waitFor</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>exitCode <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Shell command executed successfully."</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Shell command failed with exit code: "</span> <span class="token operator">+</span> exitCode<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">IOException</span> <span class="token operator">|</span> <span class="token class-name">InterruptedException</span> e<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        e<span class="token punctuation">.</span><span class="token function">printStackTrace</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>


        <span class="token class-name">BufferedReader</span> reader <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">BufferedReader</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">InputStreamReader</span><span class="token punctuation">(</span>process<span class="token punctuation">.</span><span class="token function">getInputStream</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token class-name">String</span> line<span class="token punctuation">;</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>line <span class="token operator">=</span> reader<span class="token punctuation">.</span><span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token operator">!=</span> <span class="token keyword">null</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>line<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>

        <span class="token keyword">int</span> exitCode <span class="token operator">=</span> process<span class="token punctuation">.</span><span class="token function">waitFor</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span>exitCode <span class="token operator">==</span> <span class="token number">0</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Shell command executed successfully."</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
            <span class="token class-name">System</span><span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"Shell command failed with exit code: "</span> <span class="token operator">+</span> exitCode<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">IOException</span> <span class="token operator">|</span> <span class="token class-name">InterruptedException</span> e<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        e<span class="token punctuation">.</span><span class="token function">printStackTrace</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span>
}

在上面的示例代码中,我们使用ProcessBuilder类来执行Shell命令ls -l,并通过BufferedReader来读取命令的输出。最后,我们通过waitFor()方法获取命

原文链接:https://blog.51cto.com/u_16213412/9356728
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