From 6e16a2036ec72d55ca6e280105aad2d2705cc91f Mon Sep 17 00:00:00 2001
From: Nicholas De Nova <nanovad@gmail.com>
Date: Sun, 25 Sep 2016 20:07:27 -0500
Subject: [PATCH] Add tee(1).

---
 utils/.gitignore |   1 +
 utils/Makefile   |   1 +
 utils/tee.c      | 157 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 159 insertions(+)
 create mode 100644 utils/tee.c

diff --git a/utils/.gitignore b/utils/.gitignore
index 5c8d51d1..8a5d2ffe 100644
--- a/utils/.gitignore
+++ b/utils/.gitignore
@@ -42,6 +42,7 @@ sleep
 sort
 stat
 tail
+tee
 time
 touch
 tr
diff --git a/utils/Makefile b/utils/Makefile
index 359d0c6a..53f10fe3 100644
--- a/utils/Makefile
+++ b/utils/Makefile
@@ -54,6 +54,7 @@ sleep \
 sort \
 stat \
 tail \
+tee \
 time \
 touch \
 tr \
diff --git a/utils/tee.c b/utils/tee.c
new file mode 100644
index 00000000..67399491
--- /dev/null
+++ b/utils/tee.c
@@ -0,0 +1,157 @@
+/*
+ * Copyright (c) 2016 Nicholas De Nova.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * tee.c
+ * Write stdin to stdout and the specified output files.
+ */
+
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static void compact_arguments(int* argc, char*** argv)
+{
+	for ( int i = 0; i < *argc; i++ )
+	{
+		while ( i < *argc && !(*argv)[i] )
+		{
+			for ( int n = i; n < *argc; n++ )
+				(*argv)[n] = (*argv)[n+1];
+			(*argc)--;
+		}
+	}
+}
+
+int main(int argc, char* argv[])
+{
+	bool append = false;
+	bool ignore_interrupts = false;
+
+	for ( int i = 1; i < argc; i++ )
+	{
+		const char* arg = argv[i];
+		if ( arg[0] != '-' || !arg[1] )
+			continue;
+		argv[i] = NULL;
+		if ( !strcmp(arg, "--") )
+			break;
+		if ( arg[1] != '-' )
+		{
+			char c;
+			while ( (c = *++arg) )
+				switch ( c )
+				{
+				case 'a': append = true; break;
+				case 'i': ignore_interrupts = true; break;
+				default:
+					errx(1, "unknown option -- '%c'", c);
+				}
+		}
+		else if ( !strcmp(arg, "--append") )
+			append = true;
+		else if ( !strcmp(arg, "--ignore-interrupts") )
+			ignore_interrupts = true;
+		else
+			errx(1, "unknown option: %s", arg);
+	}
+
+	compact_arguments(&argc, &argv);
+
+	if ( ignore_interrupts )
+		signal(SIGINT, SIG_IGN);
+
+	int files_count = argc - 1;
+	char buffer[65536];
+	bool ok = true;
+	bool stdout_ok = true;
+
+	int* fds = malloc(files_count * sizeof(*fds));
+	if ( !fds )
+		err(1, "malloc");
+
+	for ( int i = 0; i < files_count; i++ )
+	{
+		int oflags = O_CREAT | O_WRONLY | (append ? O_APPEND : O_TRUNC);
+		fds[i] = open(argv[i + 1], oflags, 0666);
+		if ( fds[i] < 0 )
+		{
+			warn("%s", argv[i + 1]);
+			ok = false;
+		}
+	}
+
+	while ( true )
+	{
+		ssize_t bytes_read = read(0, buffer, sizeof(buffer));
+		if ( bytes_read < 0 )
+			err(1, "stdin");
+		if ( bytes_read == 0 )
+			break;
+		ssize_t stdout_written = 0;
+		while ( stdout_written < bytes_read )
+		{
+			ssize_t stdout_left = bytes_read - stdout_written;
+			ssize_t stdout_amount;
+
+			if ( stdout_ok )
+			{
+				stdout_amount = write(1, buffer + stdout_written, stdout_left);
+				if ( stdout_amount < 0 )
+				{
+					warn("stdout");
+					stdout_ok = false;
+					ok = false;
+				}
+			}
+
+			if ( !stdout_ok )
+				stdout_amount = stdout_left;
+
+			for ( int i = 0; i < files_count; i++ )
+			{
+				if ( fds[i] < 0 )
+					continue;
+
+				ssize_t bytes_written = 0;
+				while ( bytes_written < stdout_amount )
+				{
+					char* outgoing = buffer + stdout_written + bytes_written;
+					size_t left = stdout_amount - bytes_written;
+					ssize_t amount = write(fds[i], outgoing, left);
+					if ( amount < 0 )
+					{
+						warn("%s", argv[i + 1]);
+						close(fds[i]);
+						fds[i] = -1;
+						ok = false;
+						break;
+					}
+					bytes_written += amount;
+				}
+			}
+			stdout_written += stdout_amount;
+		}
+	}
+
+	return ok ? 0 : 1;
+}