Make '--output' optional benfred#229

If no filename is specified by the user it is auto generated from
filename/pid the current time and the appropriate extension.

Cargo.toml

@@ -34,6 +34,7 @@ serde_json = "1.0"
 rand = "0.8"
 rand_distr = "0.4"
 remoteprocess = {version="0.4.2", features=["unwind"]}
+chrono = "0.4.19"
 
 [target.'cfg(unix)'.dependencies]
 termios = "0.3.2"

src/config.rs

@@ -143,7 +143,7 @@ impl Config {
                 .value_name("filename")
                 .help("Output filename")
                 .takes_value(true)
-                .required(true))
+                .required(false))
             .arg(Arg::with_name("format")
                 .short("f")
                 .long("format")

src/main.rs

@@ -13,6 +13,7 @@ extern crate lazy_static;
 extern crate libc;
 #[macro_use]
 extern crate log;
+extern crate chrono;
 #[cfg(unwind)]
 extern crate lru;
 extern crate memmap;
@@ -66,6 +67,8 @@ use stack_trace::{StackTrace, Frame};
 use console_viewer::ConsoleViewer;
 use config::{Config, FileFormat, RecordDuration};
 
+use chrono::{SecondsFormat, Local};
+
 #[cfg(unix)]
 fn permission_denied(err: &Error) -> bool {
     err.iter_chain().any(|cause| {
@@ -154,8 +157,24 @@ fn record_samples(pid: remoteprocess::Pid, config: &Config) -> Result<(), Error>
     };
 
     let filename = match config.filename.as_ref() {
-        Some(filename) => filename,
-        None => return Err(format_err!("A filename is required to record samples"))
+        Some(filename) => filename.clone(),
+        None => {
+            let ext = match config.format.as_ref() {
+                Some(FileFormat::flamegraph) => "svg",
+                Some(FileFormat::speedscope) => "json",
+                Some(FileFormat::raw) => "txt",
+                None => return Err(format_err!("A file format is required to record samples"))
+            };
+            let local_time = Local::now().to_rfc3339_opts(SecondsFormat::Secs, true);
+            let name = match config.python_program.as_ref() {
+                Some(prog) => prog[0].to_string(),
+                None  => match config.pid.as_ref() {
+                    Some(pid) => pid.to_string(),
+                    None => String::from("unknown")
+                }
+            };
+            format!("{}-{}.{}", name, local_time, ext)
+            }
     };
 
     let sampler = sampler::Sampler::new(pid, config)?;
@@ -294,25 +313,25 @@ fn record_samples(pid: remoteprocess::Pid, config: &Config) -> Result<(), Error>
     }
 
     {
-    let mut out_file = std::fs::File::create(filename)?;
+    let mut out_file = std::fs::File::create(&filename)?;
     output.write(&mut out_file)?;
     }
 
     match config.format.as_ref().unwrap() {
         FileFormat::flamegraph => {
-            println!("{}Wrote flamegraph data to '{}'. Samples: {} Errors: {}", lede, filename, samples, errors);
+            println!("{}Wrote flamegraph data to '{}'. Samples: {} Errors: {}", lede, &filename, samples, errors);
             // open generated flame graph in the browser on OSX (theory being that on linux
             // you might be SSH'ed into a server somewhere and this isn't desired, but on
             // that is pretty unlikely for osx) (note to self: xdg-open will open on linux)
             #[cfg(target_os = "macos")]
-            std::process::Command::new("open").arg(filename).spawn()?;
+            std::process::Command::new("open").arg(&filename).spawn()?;
         },
         FileFormat::speedscope =>  {
-            println!("{}Wrote speedscope file to '{}'. Samples: {} Errors: {}", lede, filename, samples, errors);
+            println!("{}Wrote speedscope file to '{}'. Samples: {} Errors: {}", lede, &filename, samples, errors);
             println!("{}Visit https://www.speedscope.app/ to view", lede);
         },
         FileFormat::raw => {
-            println!("{}Wrote raw flamegraph data to '{}'. Samples: {} Errors: {}", lede, filename, samples, errors);
+            println!("{}Wrote raw flamegraph data to '{}'. Samples: {} Errors: {}", lede, &filename, samples, errors);
             println!("{}You can use the flamegraph.pl script from https://github.com/brendangregg/flamegraph to generate a SVG", lede);
         }
     };