Output hygiene: write to stderr by default

src/bin/cargo.rs

@@ -161,26 +161,26 @@ fn execute(flags: Flags, config: &mut Config) -> CliResult {
 
     if flags.flag_version {
         let version = cargo::version();
-        println!("{}", version);
+        eprintln!("{}", version);
         if flags.flag_verbose > 0 {
-            println!("release: {}.{}.{}",
+            eprintln!("release: {}.{}.{}",
                      version.major,
                      version.minor,
                      version.patch);
             if let Some(ref cfg) = version.cfg_info {
                 if let Some(ref ci) = cfg.commit_info {
-                    println!("commit-hash: {}", ci.commit_hash);
-                    println!("commit-date: {}", ci.commit_date);
+                    eprintln!("commit-hash: {}", ci.commit_hash);
+                    eprintln!("commit-date: {}", ci.commit_date);
                 }
             }
         }
         return Ok(());
     }
 
     if flags.flag_list {
-        println!("Installed Commands:");
+        eprintln!("Installed Commands:");
         for command in list_commands(config) {
-            println!("    {}", command);
+            eprintln!("    {}", command);
         }
         return Ok(());
     }

src/bin/login.rs

@@ -68,7 +68,7 @@ pub fn execute(options: Options, config: &mut Config) -> CliResult {
                     options.flag_host.clone().unwrap_or(config.api.unwrap())
                 }
             };
-            println!("please visit {}me and paste the API Token below", host);
+            eprintln!("please visit {}me and paste the API Token below", host);
             let mut line = String::new();
             let input = io::stdin();
             input.lock().read_line(&mut line).chain_err(|| {

src/bin/pkgid.rs

@@ -74,7 +74,7 @@ pub fn execute(options: Options, config: &mut Config) -> CliResult {
     };
     let spec = spec.as_ref().map(|s| &s[..]);
     let spec = ops::pkgid(&ws, spec)?;
-    println!("{}", spec);
+    eprintln!("{}", spec);
     Ok(())
 }
 

src/bin/version.rs

@@ -21,7 +21,7 @@ Options:
 pub fn execute(_: Options, _: &mut Config) -> CliResult {
     debug!("executing; cmd=cargo-version; args={:?}", env::args().collect::<Vec<_>>());
 
-    println!("{}", cargo::version());
+    eprintln!("{}", cargo::version());
 
     Ok(())
 }

src/cargo/core/manifest.rs

@@ -355,7 +355,7 @@ impl Manifest {
     pub fn print_teapot(&self, config: &Config) {
         if let Some(teapot) = self.im_a_teapot {
             if config.cli_unstable().print_im_a_teapot {
-                println!("im-a-teapot = {}", teapot);
+                eprintln!("im-a-teapot = {}", teapot);
             }
         }
     }

src/cargo/lib.rs

@@ -143,7 +143,7 @@ pub fn exit_with_error(err: CliError, shell: &mut Shell) -> ! {
         } else if fatal {
             drop(shell.error(&error))
         } else {
-            println!("{}", error);
+            eprintln!("{}", error);
         }
 
         if !handle_cause(&error, shell) || hide {

src/cargo/ops/cargo_install.rs

@@ -558,9 +558,9 @@ pub fn install_list(dst: Option<&str>, config: &Config) -> CargoResult<()> {
     let dst = metadata(config, &dst)?;
     let list = read_crate_list(&dst)?;
     for (k, v) in list.v1.iter() {
-        println!("{}:", k);
+        eprintln!("{}:", k);
         for bin in v {
-            println!("    {}", bin);
+            eprintln!("    {}", bin);
         }
     }
     Ok(())

src/cargo/ops/cargo_new.rs

@@ -493,7 +493,7 @@ authors = [{}]
         let default_file_content : &[u8] = if i.bin {
             b"\
 fn main() {
-    println!(\"Hello, world!\");
+    eprintln!(\"Hello, world!\");
 }
 "
         } else {

src/cargo/ops/cargo_package.rs

@@ -49,7 +49,7 @@ pub fn package(ws: &Workspace,
         }).collect();
         list.sort();
         for file in list.iter() {
-            println!("{}", file.display());
+            eprintln!("{}", file.display());
         }
         return Ok(None)
     }

src/cargo/ops/cargo_rustc/mod.rs

@@ -2,7 +2,6 @@ use std::collections::{HashMap, HashSet};
 use std::env;
 use std::ffi::{OsStr, OsString};
 use std::fs;
-use std::io::{self, Write};
 use std::path::{self, PathBuf};
 use std::sync::Arc;
 
@@ -415,7 +414,7 @@ fn rustc<'a, 'cfg>(cx: &mut Context<'a, 'cfg>,
                         });
                     } else {
                         // Forward non-JSON to stderr
-                        writeln!(io::stderr(), "{}", line)?;
+                        eprintln!("{}", line);
                     }
                     Ok(())
                 }

src/cargo/ops/registry.rs

@@ -432,12 +432,12 @@ pub fn modify_owners(config: &Config, opts: &OwnersOptions) -> CargoResult<()> {
             format!("failed to list owners of crate {}", name)
         })?;
         for owner in owners.iter() {
-            print!("{}", owner.login);
+            eprint!("{}", owner.login);
             match (owner.name.as_ref(), owner.email.as_ref()) {
-                (Some(name), Some(email)) => println!(" ({} <{}>)", name, email),
+                (Some(name), Some(email)) => eprintln!(" ({} <{}>)", name, email),
                 (Some(s), None) |
-                (None, Some(s)) => println!(" ({})", s),
-                (None, None) => println!(),
+                (None, Some(s)) => eprintln!(" ({})", s),
+                (None, None) => eprintln!(),
             }
         }
     }
@@ -529,15 +529,15 @@ pub fn search(query: &str,
             }
             None => name
         };
-        println!("{}", line);
+        eprintln!("{}", line);
     }
 
     let search_max_limit = 100;
     if total_crates > u32::from(limit) && limit < search_max_limit {
-        println!("... and {} crates more (use --limit N to see more)",
+        eprintln!("... and {} crates more (use --limit N to see more)",
                  total_crates - u32::from(limit));
     } else if total_crates > u32::from(limit) && limit >= search_max_limit {
-        println!("... and {} crates more (go to http://crates.io/search?q={} to see more)",
+        eprintln!("... and {} crates more (go to http://crates.io/search?q={} to see more)",
                  total_crates - u32::from(limit),
                  percent_encode(query.as_bytes(), QUERY_ENCODE_SET));
     }

src/cargo/util/profile.rs

@@ -46,7 +46,7 @@ impl Drop for Profiler {
                 let mut last = 0;
                 for (i, &(l, time, ref msg)) in msgs.iter().enumerate() {
                     if l != lvl { continue }
-                    println!("{} {:6}ms - {}",
+                    eprintln!("{} {:6}ms - {}",
                              repeat("    ").take(lvl + 1).collect::<String>(),
                              time, msg);
 

src/doc/src/getting-started/first-steps.md

@@ -38,7 +38,7 @@ Here’s what’s in `src/main.rs`:
 
 ```rust
 fn main() {
-    println!("Hello, world!");
+    eprintln!("Hello, world!");
 }
 ```
 

src/doc/src/guide/creating-a-new-project.md

@@ -39,7 +39,7 @@ Here’s what’s in `src/main.rs`:
 
 ```rust
 fn main() {
-    println!("Hello, world!");
+    eprintln!("Hello, world!");
 }
 ```
 

src/doc/src/guide/dependencies.md

@@ -77,7 +77,7 @@ use regex::Regex;
 
 fn main() {
     let re = Regex::new(r"^\d{4}-\d{2}-\d{2}$").unwrap();
-    println!("Did our date match? {}", re.is_match("2014-01-01"));
+    eprintln!("Did our date match? {}", re.is_match("2014-01-01"));
 }
 ```
 

src/doc/src/reference/build-scripts.md

@@ -285,7 +285,7 @@ Next, let’s peek at the library itself:
 include!(concat!(env!("OUT_DIR"), "/hello.rs"));
 
 fn main() {
-    println!("{}", message());
+    eprintln!("{}", message());
 }
 ```
 

tests/cargotest/support/mod.rs

@@ -760,7 +760,7 @@ impl ham::Matcher<ProcessBuilder> for Execs {
 
 impl<'a> ham::Matcher<&'a mut ProcessBuilder> for Execs {
     fn matches(&self, process: &'a mut ProcessBuilder) -> ham::MatchResult {
-        println!("running {}", process);
+        eprintln!("running {}", process);
         let res = process.exec_with_output();
 
         match res {