From 6e9e7e7af213c9258bc4009e05bb9a3ba5d172b6 Mon Sep 17 00:00:00 2001
From: Lars Wirzenius <liw@liw.fi>
Date: Wed, 5 Jan 2022 12:39:50 +0200
Subject: feat: output file for run command

Sponsored-by: author
---
 src/bin/obnam-benchmark.rs | 23 ++++++++++++++++++-----
 src/result.rs              | 10 +++++++++-
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/src/bin/obnam-benchmark.rs b/src/bin/obnam-benchmark.rs
index 5df2aeb..41118cb 100644
--- a/src/bin/obnam-benchmark.rs
+++ b/src/bin/obnam-benchmark.rs
@@ -4,6 +4,7 @@ use obnam_benchmark::result::SuiteMeasurements;
 use obnam_benchmark::specification::Specification;
 use obnam_benchmark::suite::Suite;
 use std::fs::File;
+use std::io::Write;
 use std::path::PathBuf;
 use std::process::exit;
 use structopt::StructOpt;
@@ -61,9 +62,14 @@ struct Run {
     #[structopt(parse(from_os_str))]
     spec: PathBuf,
 
-    /// Name of file where the results will be written.
+    /// Name of file where the results will be written. Default is
+    /// stdout.
     #[structopt(long, parse(from_os_str))]
-    output: PathBuf,
+    output: Option<PathBuf>,
+
+    /// Construct output filename from benchmark run metadata.
+    #[structopt(short, long)]
+    auto: bool,
 }
 
 impl Run {
@@ -76,9 +82,16 @@ impl Run {
         for step in spec.steps().iter() {
             result.push(suite.execute(step)?);
         }
-        debug!("writing results to {}", self.output.display());
-        let output = File::create(&self.output)?;
-        serde_json::to_writer_pretty(&output, &result)?;
+
+        let output = serde_json::to_string_pretty(&result)?;
+        if let Some(filename) = &self.output {
+            std::fs::write(filename, output)?
+        } else if self.auto {
+            let filename = format!("{}_{}.json", result.hostname(), result.timestamp());
+            std::fs::write(filename, output)?
+        } else {
+            std::io::stdout().write_all(output.as_bytes())?;
+        };
         Ok(())
     }
 }
diff --git a/src/result.rs b/src/result.rs
index 4a0277e..22a49a0 100644
--- a/src/result.rs
+++ b/src/result.rs
@@ -67,13 +67,21 @@ impl SuiteMeasurements {
             measurements: vec![],
             obnam_version,
             obnam_benchmark_version: render_testament!(TESTAMENT),
-            benchmark_started: Utc::now().to_string(),
+            benchmark_started: Utc::now().format("%Y-%m-%dT%H%M%S").to_string(),
             hostname: hostname.to_string(),
             host_ram: mem.mem_total,
             host_cpus: cpu.num_cores(),
         })
     }
 
+    pub fn hostname(&self) -> &str {
+        &self.hostname
+    }
+
+    pub fn timestamp(&self) -> &str {
+        &self.benchmark_started
+    }
+
     pub fn push(&mut self, m: OpMeasurements) {
         self.measurements.push(m);
     }
-- 
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