Adding line number printing when output is piped out by domenicomastrangelo · Pull Request #2983 · sharkdp/bat

domenicomastrangelo · 2024-06-01T16:09:14Z

Updating ~~print_line function in~~ SimplePrinter to use line numbers when printing a line if line numbers are desired (self.config.style_components.numbers() / StyleComponent::LineNumbers).

This was a compatibility issue with cat until now as describe in issue #2935.

~~Updating of some integration tests was necessary as now we expect the output to contain line numbers.~~

keith-hall · 2024-06-01T19:08:31Z

tests/integration_tests.rs

        .assert()
        .success()
-        .stdout("dummy content\n");
+        .stdout("   1 dummy content\n");


I'm curious, is this really the expected behavior? The test invokes bat without any line number style component arguments. I think it should stay as it was before - according to the issue being solved, line numbers should only be displayed when piping when the command line argument was explicitly passed, no?

good catch!

I added a check for handle type here

this doesn't pass the test now, it seems like there may be an issue with the filename and the is_terminal() function or something like that

fn is_terminal(&self) -> bool

───────────────────────────────────────────
Returns true if the descriptor/handle refers to a terminal/tty.

On platforms where Rust does not know how to detect a terminal yet, this will return
false. This will also return false if an unexpected error occurred, such as from
passing an invalid file descriptor.

debugging it shows self.config.style_components.numbers() returns true, is there a different way to know if line numbers are requested that i'm missing?

My guess would be the following:

The SimplePrinter is used whenever stdout is not interactive, --color is not set to always, --decorations is not set to always and --force-colorization is not set either (see app.rs, config.rs and controller.rs). --style controls which style components (such as header or line numbers) are used. The default for --style is changes,grid,header-filename,numbers,snip. This default currently stays the same even if loop_through == true (which means that SimplePrinter will be used). Currently, SimplePrinter just does not care about --style.

So, when loop_through == true, the default for --style should be plain instead. Then your changes should work since they do when you specify --style=plain explicitly.

Thank you for the tip @einfachIrgendwer0815!

I updated the code and pushed the changes, now all the tests pass correctly and I removed all the integration test changes which were not necessary.

I also added a test for this specific case :)

…:domenicomastrangelo/bat into 2935-compatibility-issue-with-cat-piping

einfachIrgendwer0815 · 2024-11-16T11:30:04Z

I think I've found a simpler approach. The following should do the trick:

diff --git a/src/bin/bat/app.rs b/src/bin/bat/app.rs
index 8f69870f..cf385c88 100644
--- a/src/bin/bat/app.rs
+++ b/src/bin/bat/app.rs
@@ -251,9 +251,10 @@ impl App {
             loop_through: !(self.interactive_output
                 || self.matches.get_one::<String>("color").map(|s| s.as_str()) == Some("always")
                 || self
                     .matches
                     .get_one::<String>("decorations")
                     .map(|s| s.as_str())
                     == Some("always")
-                || self.matches.get_flag("force-colorization")),
+                || self.matches.get_flag("force-colorization")
+                || self.matches.get_flag("number")),
             tab_width: self

That way, whenever -n/--number is specified the default InteractivePrinter is used instead of the SimplePrinter.

Enselic · 2025-08-16T06:28:25Z

I certainly prefer things to be simple, thanks for the insight. So this PR is not needed then? I'll close it but let me know if I misunderstood something.

lmmx · 2025-10-16T12:00:29Z

I just came across this via #3316 and repeated the same idea in #3438 🙃

The issue reported in #2935 which remains in #3316 is that -n line numbers do not pipe.

It looks like a proposal was given above to continue this work (by editing or shipping as a fresh PR):

I think I've found a simpler approach. The following should do the trick:

diff --git a/src/bin/bat/app.rs b/src/bin/bat/app.rs
index 8f69870f..cf385c88 100644
--- a/src/bin/bat/app.rs
+++ b/src/bin/bat/app.rs
@@ -251,9 +251,10 @@ impl App {
             loop_through: !(self.interactive_output
                 || self.matches.get_one::<String>("color").map(|s| s.as_str()) == Some("always")
                 || self
                     .matches
                     .get_one::<String>("decorations")
                     .map(|s| s.as_str())
                     == Some("always")
-                || self.matches.get_flag("force-colorization")),
+                || self.matches.get_flag("force-colorization")
+                || self.matches.get_flag("number")),
             tab_width: self

That way, whenever -n/--number is specified the default InteractivePrinter is used instead of the SimplePrinter.

The logic for this now lives in the controller.rs module not app.rs but the same general idea as given above could be achieved by doing this at the branch point here where the SimplePrinter is gated:

bat/src/controller.rs

Lines 179 to 189 in a730eaa

    
           let mut printer: Box<dyn Printer> = if self.config.loop_through { 
        
               Box::new(SimplePrinter::new(self.config)) 
        
           } else { 
        
               Box::new(InteractivePrinter::new( 
        
                   self.config, 
        
                   self.assets, 
        
                   &mut opened_input, 
        
                   #[cfg(feature = "git")] 
        
                   &line_changes, 
        
               )?) 
        
           };

I can put that in a fresh PR (#3438), it sounds like this is a viable approach

That is the same idea I took away from reading through, emphasis added:

My initial impression is that if this were to change it may surprise people if regular piping suddenly started decorating style.

But in my case I want it to, at least when I actively pass in a style like -n. Not sure if it'd be possible to distinguish someone passing in the default style vs. it being defaulted to.

Maybe we need:

a 3rd printer, neither Simple nor Interactive, but de-coloured?

an extra config flag, to record if the user explicitly set a flag?

As an initial approximation we could simply set this based on the presence of non-default/non-empty style components

...in which case it doesn't need to be a new struct field at all

❇️ something else... ❇️

Originally posted by @lmmx in #3316

matches.get_flag indeed gives such a way to distinguish active style setting!

Domenico Mastrangelo and others added 5 commits June 1, 2024 00:50

Adding line number printing when output is piped out

bb411ab

Added CHANGELOG entry

debf7c3

cargo fmt --check

a3234bf

Fixed file_with_invalid_utf8_filename integration test

5727ccb

Merge branch 'master' into 2935-compatibility-issue-with-cat-piping

de19b52

keith-hall reviewed Jun 1, 2024

View reviewed changes

Domenico Mastrangelo and others added 10 commits June 1, 2024 22:49

Add check for non-terminal/tty handle

1eec98b

Merge branch '2935-compatibility-issue-with-cat-piping' of github.com…

9523e40

…:domenicomastrangelo/bat into 2935-compatibility-issue-with-cat-piping

cargo fmt

76832ef

Trigger Build

8ad55ab

Added current line number prefix

320f42b

Added current line number prefix

f96427f

Merge branch '2934-compatibility-issue-with-cat-piping' of github.com…

c0c1fd6

…:domenicomastrangelo/bat into 2935-compatibility-issue-with-cat-piping

Added switch to plain style as default:w in case of loop_through = true

2ba6813

Changed default to be Plain in case of loop_through

1f4d6f0

Merge branch 'master' into 2935-compatibility-issue-with-cat-piping

b13049a

Enselic closed this Aug 16, 2025

This was referenced Oct 16, 2025

feat: make output pipeable with -n, non-auto styles #3438

Merged

--style documentation is misleading #3316

Closed

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Adding line number printing when output is piped out#2983

Adding line number printing when output is piped out#2983
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