Strip ANSI escape codes when not writing to a terminal

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.

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) {

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;
 };

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

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;

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;
+}

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);