From a69ad3c769dd2fdb70c61835f21c4ae5040864c9 Mon Sep 17 00:00:00 2001
From: Fredrik Foss-Indrehus <fredrik@ffoss.net>
Date: Mon, 30 Mar 2026 20:04:50 +0200
Subject: [PATCH] Strip ANSI escape codes when not writing to a terminal

ANSI color escape codes are stripped from job output when standard
output is redirected to a pipe or file, unless CLICOLOR_FORCE is set to
a value other than "0", or TERM is set to "dumb". This matches ninja's
behavior.

Signed-off-by: Fredrik Foss-Indrehus <fredrik@ffoss.net>
---
 README.md |  6 ------
 build.c   |  5 ++++-
 build.h   |  2 +-
 samu.1    |  4 ++++
 samu.c    | 10 ++++++++++
 util.c    | 36 ++++++++++++++++++++++++++++++++++++
 util.h    |  3 +++
 7 files changed, 58 insertions(+), 8 deletions(-)

diff --git a/README.md b/README.md
index d9bc61f..791528b 100644
--- a/README.md
+++ b/README.md
@@ -39,12 +39,6 @@ are several cases where it is slightly different:
   so the first to execute depends on the address returned by `malloc`.
   This may result in build failures due to insufficiently specified
   dependencies in the project's build system.
-- samurai does not post-process the job output in any way, so if it
-  includes escape sequences they will be preserved, while ninja strips
-  escape sequences if standard output is not a terminal. Some build
-  systems, like meson, force color output from gcc by default using
-  `-fdiagnostics-color=always`, so if you plan to save the output to a
-  log, you should pass `-Db_colorout=auto` to meson.
 - samurai follows the [POSIX Utility Syntax Guidelines], in particular
   guideline 9, so it requires that any command-line options precede
   the operands. It does not do GNU-style argument permutation.
diff --git a/build.c b/build.c
index 887ba33..6a782d2 100644
--- a/build.c
+++ b/build.c
@@ -469,8 +469,11 @@ jobdone(struct job *j)
 		j->failed = true;
 	}
 	close(j->fd);
-	if (j->buf.len && (!consoleused || j->failed))
+	if (j->buf.len && (!consoleused || j->failed)) {
+		if (!buildopts.color)
+			stripansi(&j->buf);
 		fwrite(j->buf.data, 1, j->buf.len, stdout);
+	}
 	j->buf.len = 0;
 	e = j->edge;
 	if (e->pool) {
diff --git a/build.h b/build.h
index 47d6ea3..a0075ec 100644
--- a/build.h
+++ b/build.h
@@ -2,7 +2,7 @@ struct node;
 
 struct buildoptions {
 	size_t maxjobs, maxfail;
-	_Bool verbose, explain, keepdepfile, keeprsp, dryrun;
+	_Bool verbose, explain, keepdepfile, keeprsp, dryrun, color;
 	const char *statusfmt;
 	double maxload;
 };
diff --git a/samu.1 b/samu.1
index d2f711e..7672690 100644
--- a/samu.1
+++ b/samu.1
@@ -245,6 +245,10 @@ Elapsed time in seconds (to 3 decimal places).
 .It Cm %%
 The '%' character.
 .El
+.It Ev CLICOLOR_FORCE
+If set to a value other than "0", force ANSI color escape codes to be printed even if standard output is not a terminal.
+.It Ev TERM
+If set to "dumb", disable ANSI color escape codes.
 .El
 .Sh SEE ALSO
 .Xr make 1
diff --git a/samu.c b/samu.c
index 0c389bc..75ae26a 100644
--- a/samu.c
+++ b/samu.c
@@ -3,6 +3,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include "arg.h"
 #include "build.h"
 #include "deps.h"
@@ -145,6 +146,8 @@ main(int argc, char *argv[])
 	struct node *n;
 	long num;
 	int tries;
+	const char *term, *clicolor_force;
+
 
 	argv0 = progname(argv[0], "samu");
 	parseenvargs(getenv("SAMUFLAGS"));
@@ -218,6 +221,13 @@ main(int argc, char *argv[])
 	if (!buildopts.statusfmt)
 		buildopts.statusfmt = "[%s/%t] ";
 
+	term = getenv("TERM");
+	clicolor_force = getenv("CLICOLOR_FORCE");
+
+	buildopts.color = isatty(1) && term && strcmp(term, "dumb") != 0;
+	if (!buildopts.color)
+		buildopts.color = clicolor_force && strcmp(clicolor_force, "0") != 0;
+
 	setvbuf(stdout, NULL, _IOLBF, 0);
 
 	tries = 0;
diff --git a/util.c b/util.c
index 8ee3ddd..522ca86 100644
--- a/util.c
+++ b/util.c
@@ -225,3 +225,39 @@ writefile(const char *name, struct string *s)
 
 	return ret;
 }
+
+static int
+islatinalpha(int c)
+{
+	return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z');
+}
+
+void
+stripansi(struct buffer *buf)
+{
+	char *read = buf->data;
+	char *write = buf->data;
+	char *end = buf->data + buf->len;
+
+	if (!buf->data)
+		return;
+
+	while (read < end) {
+		if (*read != '\033') {
+			*write++ = *read++;
+			continue;
+		}
+		if (read + 1 >= end)
+			break;
+		if (*(read + 1) != '[') {
+			read++;
+			continue;
+		}
+		read += 2;
+		while (read < end && !islatinalpha(*read))
+			read++;
+		if (read < end)
+			read++;
+	}
+	buf->len = write - buf->data;
+}
diff --git a/util.h b/util.h
index 5da348c..aa4eb84 100644
--- a/util.h
+++ b/util.h
@@ -40,3 +40,6 @@ void delevalstr(void *);
 void canonpath(struct string *);
 /* write a new file with the given name and contents */
 int writefile(const char *, struct string *);
+
+/* strip ANSI escape codes from buffer in-place */
+void stripansi(struct buffer *buf);