From 2e33b2a55355d17c2f20b0eab9a014a7687497f6 Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Tue, 6 Aug 2019 14:34:34 -0400
Subject: initial implementation

---
 tee.c | 92 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 tee.c

diff --git a/tee.c b/tee.c
new file mode 100644
index 0000000..7159ae0
--- /dev/null
+++ b/tee.c
@@ -0,0 +1,92 @@
+/*
+ * UNG's Not GNU
+ *
+ * Copyright (c) 2011-2019, Jakob Kaivo <jkk@ung.org>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#define _POSIX_C_SOURCE 2
+#include <errno.h>
+#include <locale.h>
+#include <signal.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#if FOPEN_MAX < 13
+#undef FOPEN_MAX
+#define FOPEN_MAX 13
+#endif
+
+static FILE *outputs[FOPEN_MAX];
+static int noutputs = 0;
+
+static int addoutput(const char *path, const char *mode)
+{
+	outputs[noutputs] = fopen(path, mode);
+	if (outputs[noutputs] == NULL) {
+		fprintf(stderr, "tee: %s: %s\n", path, strerror(errno));
+		return 1;
+	}
+
+	noutputs++;
+	return 0;
+}
+
+int main(int argc, char *argv[])
+{
+	setlocale(LC_ALL, "");
+	char *mode = "w";
+
+	int c;
+	while ((c = getopt(argc, argv, "ai")) != -1) {
+		switch (c) {
+		case 'a':
+			mode = "a";
+			break;
+
+		case 'i':
+			signal(SIGINT, SIG_IGN);
+			break;
+
+		default:
+			return 1;
+		}
+	}
+
+	if (argc - optind > FOPEN_MAX) {
+		fprintf(stderr, "tee: too many outputs (max %d)\n", FOPEN_MAX);
+		return 1;
+	}
+
+	int r = 0;
+	while (optind < argc) {
+		r |= addoutput(argv[optind++], mode);
+	}
+
+	while ((c = getchar()) != EOF) {
+		fputc(c, stdout);
+		for (int i = 0; i < noutputs; i++) {
+			fputc(c, outputs[i]);
+		}
+	}
+
+	return r;
+}
-- 
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