Added a CLI command to report console output

changelog.html

@@ -68,6 +68,8 @@ Upcoming changes</a>
     Display class loading statistics in <code>/computer/<i>name</i>/systemInfo</code>.
   <li class=rfe>
     Added <tt>list-plugins</tt> CLI command.
+  <li class=rfe>
+    Added <tt>console</tt> CLI command that dumps console output from a build.
 </ul>
 </div><!--=TRUNK-END=-->
 

core/src/main/java/hudson/cli/ConsoleCommand.java

+package hudson.cli;
+
+import hudson.Extension;
+import hudson.console.AnnotatedLargeText;
+import hudson.model.AbstractBuild;
+import hudson.model.AbstractProject;
+import hudson.model.Item;
+import hudson.model.PermalinkProjectAction.Permalink;
+import hudson.util.IOUtils;
+import org.kohsuke.args4j.Argument;
+import org.kohsuke.args4j.CmdLineException;
+import org.kohsuke.args4j.Option;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.io.PrintStream;
+
+/**
+ * cat/tail/head of the console output.
+ *
+ * @author Kohsuke Kawaguchi
+ */
+@Extension
+public class ConsoleCommand extends CLICommand {
+    @Override
+    public String getShortDescription() {
+        return "Retrieves console output of a build";
+    }
+
+    @Argument(metaVar="JOB",usage="Name of the job",required=true)
+    public AbstractProject<?,?> job;
+
+    @Argument(metaVar="BUILD",usage="Build number or permalink to point to the build. Defaults to the last build",required=false,index=1)
+    public String build="lastBuild";
+
+    @Option(name="-f",usage="If the build is in progress, stay around and append console output as it comes, like 'tail -f'")
+    public boolean follow = false;
+
+    @Option(name="-n",metaVar="N",usage="Display the last N lines")
+    public int n = -1;
+
+    protected int run() throws Exception {
+        job.checkPermission(Item.BUILD);
+
+        AbstractBuild<?,?> run;
+
+        try {
+            int n = Integer.parseInt(build);
+            run = job.getBuildByNumber(n);
+            if (run==null)
+                throw new CmdLineException("No such build #"+n);
+        } catch (NumberFormatException e) {
+            // maybe a permalink?
+            Permalink p = job.getPermalinks().get(build);
+            if (p!=null) {
+                run = (AbstractBuild)p.resolve(job);
+                if (run==null)
+                    throw new CmdLineException("Permalink "+build+" produced no build");
+            } else {
+                Permalink nearest = job.getPermalinks().findNearest(build);
+                throw new CmdLineException(String.format("Not sure what you meant by \"%s\". Did you mean \"%s\"?", build, nearest.getId()));
+            }
+        }
+
+        OutputStreamWriter w = new OutputStreamWriter(stdout, getClientCharset());
+        try {
+            long pos = n>=0 ? seek(run) : 0;
+
+            if (follow) {
+                AnnotatedLargeText logText;
+                do {
+                    logText = run.getLogText();
+                    pos = logText.writeLogTo(pos, w);
+                } while (!logText.isComplete());
+            } else {
+                InputStream in = run.getLogInputStream();
+                IOUtils.skip(in,pos);
+                IOUtils.copy(new InputStreamReader(in,run.getCharset()),w);
+            }
+        } finally {
+            w.flush(); // this pointless flush needed to work around SSHD-154
+            w.close();
+        }
+
+        return 0;
+    }
+
+    /**
+     * Find the byte offset in the log input stream that marks "last N lines".
+     */
+    private long seek(AbstractBuild<?, ?> run) throws IOException {
+        class RingBuffer {
+            long[] lastNlines = new long[n];
+            int ptr=0;
+
+            RingBuffer() {
+                for (int i=0; i<n; i++)
+                    lastNlines[i] = -1;
+            }
+
+            void add(long pos) {
+                lastNlines[ptr] = pos;
+                ptr = (ptr+1)%lastNlines.length;
+            }
+
+            long get() {
+                long v = lastNlines[ptr];
+                if (v<0)    return lastNlines[0];   // didn't even wrap around
+                return v;
+            }
+        }
+        RingBuffer rb = new RingBuffer();
+
+        InputStream in = run.getLogInputStream();
+        try {
+            byte[] buf = new byte[4096];
+            int len;
+            byte prev=0;
+            long pos=0;
+            boolean prevIsNL = false;
+            while ((len=in.read(buf))>=0) {
+                for (int i=0; i<len; i++) {
+                    byte ch = buf[i];
+                    boolean isNL = ch=='\r' || ch=='\n';
+                    if (!isNL && prevIsNL)  rb.add(pos);
+                    if (isNL && prevIsNL && !(prev=='\r' && ch=='\n'))  rb.add(pos);
+                    pos++;
+                    prev = ch;
+                    prevIsNL = isNL;
+                }
+            }
+
+            return rb.get();
+        } finally {
+            IOUtils.closeQuietly(in);
+        }
+    }
+
+    @Override
+    protected void printUsageSummary(PrintStream stderr) {
+        stderr.println(
+            "Produces the console output of a specific build to stdout, as if you are doing 'cat build.log'"
+        );
+    }
+}