从 Java 运行 Grep 命令
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Running Grep command from java
提问by Ramu Pasupuleti
I want to run grep command from java.
我想从 java 运行 grep 命令。
Here is what I had tried. Please let me know, why it is not displaying ouput.
这是我尝试过的。请让我知道，为什么它不显示输出。
public static void main(String args[]) throws IOException{
Runtime rt = Runtime.getRuntime();
String[] cmd = { "/bin/sh", "-c", "grep 'Report Process started' server.log|wc -l" };
Process proc = rt.exec(cmd);
BufferedReader is = new BufferedReader(new InputStreamReader(proc.getInputStream()));
String line;
while ((line = is.readLine()) != null) {
System.out.println(line);
}
System.out.println("Done");
}
采纳答案by anubhava
You don't need to pipe grep's output to wc -l. Just use grep -clike this:
您不需要将 grep 的输出通过管道传输到wc -l. 只需grep -c像这样使用：
String[] cmd = {"/bin/sh", "-c", "grep -c 'Report Process started' /path/to/server.log"};
Though I must say that doing this right inside Java is much cleaner. Consider code like this:
尽管我必须说在 Java 中正确执行此操作要干净得多。考虑这样的代码：
String logdata = new Scanner(new File("/path/to/server.log")).useDelimiter("\Z").next();
final String needle = "Report Process started";
int occurrences = 0;
int index = 0;
while (index < logdata.length() && (index = logdata.indexOf(needle, index)) >= 0) {
occurrences++;
index += needle.length();
}
回答by vels4j
You must check for any errors.
您必须检查是否有任何错误。
private static void printStream(InputStream in) throws IOException {
BufferedReader is = new BufferedReader(new InputStreamReader(in));
String line;
while ((line = is.readLine()) != null) {
System.out.println(line);
}
}
public static void main(String args[]) {
try {
Runtime rt = Runtime.getRuntime();
String[] cmd = {"/bin/sh", "-c", "grep 'Report Process started' server.log|wc -l"};
Process proc = rt.exec(cmd);
printStream(proc.getInputStream());
System.out.println("Error : ");
printStream(proc.getErrorStream());
} catch (Exception ex) {
ex.printStackTrace();
}
}
