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<!DOCTYPE html> < html lang = "en" > < head > < meta charset = "utf-8" > < meta name = "viewport" content = "width=device-width, initial-scale=1.0" > < meta name = "generator" content = "rustdoc" > < meta name = "description" content = "Prints to `stdout`." > < title > print in anstream - Rust< / title > < script > if ( window . location . protocol !== "file:" ) document . head . insertAdjacentHTML ( "beforeend" , "SourceSerif4-Regular-46f98efaafac5295.ttf.woff2,FiraSans-Regular-018c141bf0843ffd.woff2,FiraSans-Medium-8f9a781e4970d388.woff2,SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2,SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2" . split ( "," ) . map ( f => ` <link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/ ${ f } "> ` ) . join ( "" ) ) < / script > < link rel = "stylesheet" href = "../static.files/normalize-76eba96aa4d2e634.css" > < link rel = "stylesheet" href = "../static.files/rustdoc-dd39b87e5fcfba68.css" > < meta name = "rustdoc-vars" data-root-path = "../" data-static-root-path = "../static.files/" data-current-crate = "anstream" data-themes = "" data-resource-suffix = "" data-rustdoc-version = "1.80.0 (051478957 2024-07-21)" data-channel = "1.80.0" data-search-js = "search-d52510db62a78183.js" data-settings-js = "settings-4313503d2e1961c2.js" > < script src = "../static.files/storage-118b08c4c78b968e.js" > < / script > < script defer src = "sidebar-items.js" > < / script > < script defer src = "../static.files/main-20a3ad099b048cf2.js" > < / script > < noscript > < link rel = "stylesheet" href = "../static.files/noscript-df360f571f6edeae.css" > < / noscript > < link rel = "alternate icon" type = "image/png" href = "../static.files/favicon-32x32-422f7d1d52889060.png" > < link rel = "icon" type = "image/svg+xml" href = "../static.files/favicon-2c020d218678b618.svg" > < / head > < body class = "rustdoc macro" > <!-- [if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif] --> < nav class = "mobile-topbar" > < button class = "sidebar-menu-toggle" title = "show sidebar" > < / button > < / nav > < nav class = "sidebar" > < div class = "sidebar-crate" > < h2 > < a href = "../anstream/index.html" > anstream< / a > < span class = "version" > 0.6.14< / span > < / h2 > < / div > < div class = "sidebar-elems" > < / div > < / nav > < div class = "sidebar-resizer" > < / div > < main > < div class = "width-limiter" > < rustdoc-search > < / rustdoc-search > < section id = "main-content" class = "content" > < div class = "main-heading" > < h1 > Macro < a href = "index.html" > anstream< / a > ::< wbr > < a class = "macro" href = "#" > print< / a > < button id = "copy-path" title = "Copy item path to clipboard" > Copy item path< / button > < / h1 > < span class = "out-of-band" > < a class = "src" href = "../src/anstream/macros.rs.html#61-88" > source< / a > · < button id = "toggle-all-docs" title = "collapse all docs" > [< span > − < / span > ]< / button > < / span > < / div > < pre class = "rust item-decl" > < span class = "macro" > macro_rules!< / span > print {
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($(< span class = "macro-nonterminal" > $arg< / span > :tt)< span class = "kw-2" > *< / span > ) => { ... };
}< / pre > < details class = "toggle top-doc" open > < summary class = "hideme" > < span > Expand description< / span > < / summary > < div class = "docblock" > < p > Prints to < a href = "fn.stdout.html" title = "fn anstream::stdout" > < code > stdout< / code > < / a > .< / p >
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< p > Equivalent to the < a href = "https://doc.rust-lang.org/1.80.0/std/macro.println.html" title = "macro std::println" > < code > println!< / code > < / a > macro except that a newline is not printed at
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the end of the message.< / p >
< p > Note that stdout is frequently line-buffered by default so it may be
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necessary to use < a href = "https://doc.rust-lang.org/1.80.0/std/io/trait.Write.html#tymethod.flush" title = "method std::io::Write::flush" > < code > std::io::Write::flush()< / code > < / a > to ensure the output is emitted
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immediately.< / p >
< p > < strong > NOTE:< / strong > The < code > print!< / code > macro will lock the standard output on each call. If you call
< code > print!< / code > within a hot loop, this behavior may be the bottleneck of the loop.
To avoid this, lock stdout with < a href = "struct.AutoStream.html#method.lock" title = "method anstream::AutoStream::lock" > < code > AutoStream::lock< / code > < / a > :< / p >
< div class = "example-wrap" > < pre class = "rust rust-example-rendered" > < code > < span class = "kw" > use < / span > std::io::Write < span class = "kw" > as _< / span > ;
< span class = "kw" > let < / span > < span class = "kw-2" > mut < / span > lock = anstream::stdout().lock();
< span class = "macro" > write!< / span > (lock, < span class = "string" > "hello world"< / span > ).unwrap();< / code > < / pre > < / div >
< p > Use < code > print!< / code > only for the primary output of your program. Use
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< a href = "https://doc.rust-lang.org/1.80.0/std/macro.eprint.html" title = "macro std::eprint" > < code > eprint!< / code > < / a > instead to print error and progress messages.< / p >
< p > < strong > NOTE:< / strong > Not all < code > print!< / code > calls will be captured in tests like < a href = "https://doc.rust-lang.org/1.80.0/std/macro.print.html" title = "macro std::print" > < code > std::print!< / code > < / a > < / p >
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< ul >
< li > Capturing will automatically be activated in test binaries< / li >
< li > Otherwise, only when the < code > test< / code > feature is enabled< / li >
< / ul >
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< h2 id = "panics" > < a class = "doc-anchor" href = "#panics" > §< / a > Panics< / h2 >
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< p > Panics if writing to < code > stdout< / code > fails for any reason < strong > except< / strong > broken pipe.< / p >
< p > Writing to non-blocking stdout can cause an error, which will lead
this macro to panic.< / p >
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< h2 id = "examples" > < a class = "doc-anchor" href = "#examples" > §< / a > Examples< / h2 >
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< div class = "example-wrap" > < pre class = "rust rust-example-rendered" > < code > < span class = "kw" > use < / span > std::io::Write < span class = "kw" > as _< / span > ;
< span class = "kw" > use < / span > anstream::print;
< span class = "kw" > use < / span > anstream::stdout;
< span class = "macro" > print!< / span > (< span class = "string" > "this "< / span > );
< span class = "macro" > print!< / span > (< span class = "string" > "will "< / span > );
< span class = "macro" > print!< / span > (< span class = "string" > "be "< / span > );
< span class = "macro" > print!< / span > (< span class = "string" > "on "< / span > );
< span class = "macro" > print!< / span > (< span class = "string" > "the "< / span > );
< span class = "macro" > print!< / span > (< span class = "string" > "same "< / span > );
< span class = "macro" > print!< / span > (< span class = "string" > "line "< / span > );
stdout().flush().unwrap();
< span class = "macro" > print!< / span > (< span class = "string" > "this string has a newline, why not choose println! instead?\n"< / span > );
stdout().flush().unwrap();< / code > < / pre > < / div >
< / div > < / details > < / section > < / div > < / main > < / body > < / html >
