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diff --git a/COPYING b/COPYING
new file mode 100644
index 0000000..d159169
--- /dev/null
+++ b/COPYING
@@ -0,0 +1,339 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 2, June 1991
+
+ Copyright (C) 1989, 1991 Free Software Foundation, Inc.,
+ 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
+
+  The licenses for most software are designed to take away your
+freedom to share and change it.  By contrast, the GNU General Public
+License is intended to guarantee your freedom to share and change free
+software--to make sure the software is free for all its users.  This
+General Public License applies to most of the Free Software
+Foundation's software and to any other program whose authors commit to
+using it.  (Some other Free Software Foundation software is covered by
+the GNU Lesser General Public License instead.)  You can apply it to
+your programs, too.
+
+  When we speak of free software, we are referring to freedom, not
+price.  Our General Public Licenses are designed to make sure that you
+have the freedom to distribute copies of free software (and charge for
+this service if you wish), that you receive source code or can get it
+if you want it, that you can change the software or use pieces of it
+in new free programs; and that you know you can do these things.
+
+  To protect your rights, we need to make restrictions that forbid
+anyone to deny you these rights or to ask you to surrender the rights.
+These restrictions translate to certain responsibilities for you if you
+distribute copies of the software, or if you modify it.
+
+  For example, if you distribute copies of such a program, whether
+gratis or for a fee, you must give the recipients all the rights that
+you have.  You must make sure that they, too, receive or can get the
+source code.  And you must show them these terms so they know their
+rights.
+
+  We protect your rights with two steps: (1) copyright the software, and
+(2) offer you this license which gives you legal permission to copy,
+distribute and/or modify the software.
+
+  Also, for each author's protection and ours, we want to make certain
+that everyone understands that there is no warranty for this free
+software.  If the software is modified by someone else and passed on, we
+want its recipients to know that what they have is not the original, so
+that any problems introduced by others will not reflect on the original
+authors' reputations.
+
+  Finally, any free program is threatened constantly by software
+patents.  We wish to avoid the danger that redistributors of a free
+program will individually obtain patent licenses, in effect making the
+program proprietary.  To prevent this, we have made it clear that any
+patent must be licensed for everyone's free use or not licensed at all.
+
+  The precise terms and conditions for copying, distribution and
+modification follow.
+
+                    GNU GENERAL PUBLIC LICENSE
+   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
+
+  0. This License applies to any program or other work which contains
+a notice placed by the copyright holder saying it may be distributed
+under the terms of this General Public License.  The "Program", below,
+refers to any such program or work, and a "work based on the Program"
+means either the Program or any derivative work under copyright law:
+that is to say, a work containing the Program or a portion of it,
+either verbatim or with modifications and/or translated into another
+language.  (Hereinafter, translation is included without limitation in
+the term "modification".)  Each licensee is addressed as "you".
+
+Activities other than copying, distribution and modification are not
+covered by this License; they are outside its scope.  The act of
+running the Program is not restricted, and the output from the Program
+is covered only if its contents constitute a work based on the
+Program (independent of having been made by running the Program).
+Whether that is true depends on what the Program does.
+
+  1. You may copy and distribute verbatim copies of the Program's
+source code as you receive it, in any medium, provided that you
+conspicuously and appropriately publish on each copy an appropriate
+copyright notice and disclaimer of warranty; keep intact all the
+notices that refer to this License and to the absence of any warranty;
+and give any other recipients of the Program a copy of this License
+along with the Program.
+
+You may charge a fee for the physical act of transferring a copy, and
+you may at your option offer warranty protection in exchange for a fee.
+
+  2. You may modify your copy or copies of the Program or any portion
+of it, thus forming a work based on the Program, and copy and
+distribute such modifications or work under the terms of Section 1
+above, provided that you also meet all of these conditions:
+
+    a) You must cause the modified files to carry prominent notices
+    stating that you changed the files and the date of any change.
+
+    b) You must cause any work that you distribute or publish, that in
+    whole or in part contains or is derived from the Program or any
+    part thereof, to be licensed as a whole at no charge to all third
+    parties under the terms of this License.
+
+    c) If the modified program normally reads commands interactively
+    when run, you must cause it, when started running for such
+    interactive use in the most ordinary way, to print or display an
+    announcement including an appropriate copyright notice and a
+    notice that there is no warranty (or else, saying that you provide
+    a warranty) and that users may redistribute the program under
+    these conditions, and telling the user how to view a copy of this
+    License.  (Exception: if the Program itself is interactive but
+    does not normally print such an announcement, your work based on
+    the Program is not required to print an announcement.)
+
+These requirements apply to the modified work as a whole.  If
+identifiable sections of that work are not derived from the Program,
+and can be reasonably considered independent and separate works in
+themselves, then this License, and its terms, do not apply to those
+sections when you distribute them as separate works.  But when you
+distribute the same sections as part of a whole which is a work based
+on the Program, the distribution of the whole must be on the terms of
+this License, whose permissions for other licensees extend to the
+entire whole, and thus to each and every part regardless of who wrote it.
+
+Thus, it is not the intent of this section to claim rights or contest
+your rights to work written entirely by you; rather, the intent is to
+exercise the right to control the distribution of derivative or
+collective works based on the Program.
+
+In addition, mere aggregation of another work not based on the Program
+with the Program (or with a work based on the Program) on a volume of
+a storage or distribution medium does not bring the other work under
+the scope of this License.
+
+  3. You may copy and distribute the Program (or a work based on it,
+under Section 2) in object code or executable form under the terms of
+Sections 1 and 2 above provided that you also do one of the following:
+
+    a) Accompany it with the complete corresponding machine-readable
+    source code, which must be distributed under the terms of Sections
+    1 and 2 above on a medium customarily used for software interchange; or,
+
+    b) Accompany it with a written offer, valid for at least three
+    years, to give any third party, for a charge no more than your
+    cost of physically performing source distribution, a complete
+    machine-readable copy of the corresponding source code, to be
+    distributed under the terms of Sections 1 and 2 above on a medium
+    customarily used for software interchange; or,
+
+    c) Accompany it with the information you received as to the offer
+    to distribute corresponding source code.  (This alternative is
+    allowed only for noncommercial distribution and only if you
+    received the program in object code or executable form with such
+    an offer, in accord with Subsection b above.)
+
+The source code for a work means the preferred form of the work for
+making modifications to it.  For an executable work, complete source
+code means all the source code for all modules it contains, plus any
+associated interface definition files, plus the scripts used to
+control compilation and installation of the executable.  However, as a
+special exception, the source code distributed need not include
+anything that is normally distributed (in either source or binary
+form) with the major components (compiler, kernel, and so on) of the
+operating system on which the executable runs, unless that component
+itself accompanies the executable.
+
+If distribution of executable or object code is made by offering
+access to copy from a designated place, then offering equivalent
+access to copy the source code from the same place counts as
+distribution of the source code, even though third parties are not
+compelled to copy the source along with the object code.
+
+  4. You may not copy, modify, sublicense, or distribute the Program
+except as expressly provided under this License.  Any attempt
+otherwise to copy, modify, sublicense or distribute the Program is
+void, and will automatically terminate your rights under this License.
+However, parties who have received copies, or rights, from you under
+this License will not have their licenses terminated so long as such
+parties remain in full compliance.
+
+  5. You are not required to accept this License, since you have not
+signed it.  However, nothing else grants you permission to modify or
+distribute the Program or its derivative works.  These actions are
+prohibited by law if you do not accept this License.  Therefore, by
+modifying or distributing the Program (or any work based on the
+Program), you indicate your acceptance of this License to do so, and
+all its terms and conditions for copying, distributing or modifying
+the Program or works based on it.
+
+  6. Each time you redistribute the Program (or any work based on the
+Program), the recipient automatically receives a license from the
+original licensor to copy, distribute or modify the Program subject to
+these terms and conditions.  You may not impose any further
+restrictions on the recipients' exercise of the rights granted herein.
+You are not responsible for enforcing compliance by third parties to
+this License.
+
+  7. If, as a consequence of a court judgment or allegation of patent
+infringement or for any other reason (not limited to patent issues),
+conditions are imposed on you (whether by court order, agreement or
+otherwise) that contradict the conditions of this License, they do not
+excuse you from the conditions of this License.  If you cannot
+distribute so as to satisfy simultaneously your obligations under this
+License and any other pertinent obligations, then as a consequence you
+may not distribute the Program at all.  For example, if a patent
+license would not permit royalty-free redistribution of the Program by
+all those who receive copies directly or indirectly through you, then
+the only way you could satisfy both it and this License would be to
+refrain entirely from distribution of the Program.
+
+If any portion of this section is held invalid or unenforceable under
+any particular circumstance, the balance of the section is intended to
+apply and the section as a whole is intended to apply in other
+circumstances.
+
+It is not the purpose of this section to induce you to infringe any
+patents or other property right claims or to contest validity of any
+such claims; this section has the sole purpose of protecting the
+integrity of the free software distribution system, which is
+implemented by public license practices.  Many people have made
+generous contributions to the wide range of software distributed
+through that system in reliance on consistent application of that
+system; it is up to the author/donor to decide if he or she is willing
+to distribute software through any other system and a licensee cannot
+impose that choice.
+
+This section is intended to make thoroughly clear what is believed to
+be a consequence of the rest of this License.
+
+  8. If the distribution and/or use of the Program is restricted in
+certain countries either by patents or by copyrighted interfaces, the
+original copyright holder who places the Program under this License
+may add an explicit geographical distribution limitation excluding
+those countries, so that distribution is permitted only in or among
+countries not thus excluded.  In such case, this License incorporates
+the limitation as if written in the body of this License.
+
+  9. The Free Software Foundation may publish revised and/or new versions
+of the General Public License from time to time.  Such new versions will
+be similar in spirit to the present version, but may differ in detail to
+address new problems or concerns.
+
+Each version is given a distinguishing version number.  If the Program
+specifies a version number of this License which applies to it and "any
+later version", you have the option of following the terms and conditions
+either of that version or of any later version published by the Free
+Software Foundation.  If the Program does not specify a version number of
+this License, you may choose any version ever published by the Free Software
+Foundation.
+
+  10. If you wish to incorporate parts of the Program into other free
+programs whose distribution conditions are different, write to the author
+to ask for permission.  For software which is copyrighted by the Free
+Software Foundation, write to the Free Software Foundation; we sometimes
+make exceptions for this.  Our decision will be guided by the two goals
+of preserving the free status of all derivatives of our free software and
+of promoting the sharing and reuse of software generally.
+
+                            NO WARRANTY
+
+  11. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
+FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW.  EXCEPT WHEN
+OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
+PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
+OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  THE ENTIRE RISK AS
+TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU.  SHOULD THE
+PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
+REPAIR OR CORRECTION.
+
+  12. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
+REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
+INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
+OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
+TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
+YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
+PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGES.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+convey the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software; you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation; either version 2 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..5e2eb7b
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,19 @@
+PREFIX ?= /usr/local
+DESTDIR ?=
+BINDIR ?= $(PREFIX)/bin
+MANDIR ?= $(PREFIX)/share/man
+
+CFLAGS ?= -O3 -march=native
+CFLAGS += -std=c99 -Wall
+
+all: cscript
+
+cscript:
+
+install: cscript
+	@install -v -d "$(DESTDIR)$(BINDIR)" && install -v -m 0755 cscript "$(DESTDIR)$(BINDIR)/cscript"
+
+clean:
+	rm -f cscript
+
+.PHONY: all clean install
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..3ea230e
--- /dev/null
+++ b/README.md
@@ -0,0 +1,37 @@
+# cscript
+#### by [Jason A. Donenfeld](mailto:Jason@zx2c4.com)
+
+`cscript` executes C code from stdin using any variety of compiler arguments. It can be used from the command line:
+
+```
+$ echo 'main(){puts("hello world");}' | cscript
+```
+
+Or it can be used at the top of scripts:
+
+```
+ #!/usr/bin/cscript
+ main(){puts("hello world");}
+```
+
+One might even register .c as an executable file type:
+
+```
+# echo ':cfile:E::c::/usr/bin/cscript:' > /proc/sys/fs/binfmt_misc/register
+$ echo 'main(){puts("hello world");}' > a.c
+$ chmod +x a.c
+$ ./a.c
+```
+
+It respects the `CC` environment variable, and does not create any temporary dentries that need to be cleaned up ever.
+
+### Building
+
+```
+$ make
+$ sudo make install PREFIX=/usr
+```
+
+### License
+
+This project is released under the [GPLv2](COPYING).
diff --git a/cscript.c b/cscript.c
new file mode 100644
index 0000000..c7dbcf5
--- /dev/null
+++ b/cscript.c
@@ -0,0 +1,109 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <fcntl.h>
+
+int main(int argc, char *argv[], char *envp[])
+{
+	int fd, fd2, input = -1, pipes[2] = { 0 }, status;
+	pid_t compiler_pid;
+	char *output_path;
+
+	if (argc > 1 && argv[argc - 1][0] != '-') {
+		input = open(argv[1], O_RDONLY);
+		++argv;
+		--argc;
+		if (input < 0) {
+			perror("Error: unable to open input file");
+			return 1;
+		}
+		if (pipe(pipes) < 0) {
+			perror("Error: unable to open filter pipe");
+			return 1;
+		}
+	}
+
+	fd = open(getenv("HOME") ?: getenv("TMPDIR") ?: "/tmp", O_TMPFILE | O_EXCL | O_RDWR, S_IWUSR | S_IRUSR);
+	if (fd < 0) {
+		perror("Error: unable to create temporary inode");
+		return 1;
+	}
+	if (asprintf(&output_path, "/proc/self/fd/%d", fd) < 0) {
+		perror("Error: unable to allocate memory for fd string");
+		return 1;
+	}
+
+	compiler_pid = fork();
+	if (compiler_pid < 0) {
+		perror("Error: unable to fork for compiler");
+		return 1;
+	}
+
+	if (compiler_pid == 0) {
+		const char *cc = getenv("CC") ?: "gcc";
+		close(input);
+		if (pipes[0] != 0) {
+			close(pipes[1]);
+			if (dup2(pipes[0], 0) < 0) {
+				perror("Error: unable to duplicate pipe fd");
+				_exit(1);
+			}
+			close(pipes[0]);
+		}
+		execlp(cc, cc, "-xc", "-o", output_path, "-", NULL);
+		_exit(1);
+	}
+
+	if (input != -1) {
+		char beginning[2];
+		ssize_t len;
+
+		close(pipes[0]);
+		len = read(input, beginning, 2);
+		if (len < 0) {
+			perror("Error: unable to read from input file");
+			return 1;
+		} else if (len == 2 && beginning[0] == '#' && beginning[1] == '!')
+			len = write(pipes[1], "//", 2);
+		else if (len > 0)
+			len = write(pipes[1], beginning, len);
+		if (len < 0) {
+			perror("Error: unable to write input preamble");
+			return 1;
+		}
+		if (splice(input, NULL, pipes[1], NULL, 0x7fffffff, 0) < 0) {
+			perror("Error: unable to splice input to compiler child");
+			return 1;
+		}
+		close(pipes[1]);
+	}
+
+	if (waitpid(compiler_pid, &status, 0) != compiler_pid || (!WIFEXITED(status) || WEXITSTATUS(status))) {
+		fprintf(stderr, "Error: compiler process did not complete successfully\n");
+		return 1;
+	}
+
+	fd2 = open(output_path, O_RDONLY);
+	if (fd2 < 0) {
+		perror("Error: unable to reopen temporary inode");
+		return 1;
+	}
+	close(fd);
+
+	if (fexecve(fd2, argv, envp) < 0) {
+		perror("Error: could not execute compiled program");
+		return 1;
+	}
+	return 0;
+}
diff --git a/example.c b/example.c
new file mode 100755
index 0000000..9db558a
--- /dev/null
+++ b/example.c
@@ -0,0 +1,99 @@
+#!/usr/bin/env cscript
+
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <inttypes.h>
+#include <errno.h>
+
+enum { PASCALS_TRIANGLE_MAX_ROWS_FOR_UINT64 = 68 };
+
+static uint64_t **create_pascals_triangle(size_t num_rows)
+{
+	uint64_t **triangle;
+	size_t i, j;
+
+	if (!num_rows || num_rows > PASCALS_TRIANGLE_MAX_ROWS_FOR_UINT64) {
+		errno = EINVAL;
+		return NULL;
+	}
+	
+	triangle = reallocarray(NULL, num_rows + 1, sizeof(*triangle));
+	if (!triangle)
+		return NULL;
+	triangle[num_rows] = NULL;
+
+	for (i = 0; i < num_rows; ++i) {
+		triangle[i] = reallocarray(NULL, i + 1, sizeof(**triangle));
+		if (!triangle[i]) {
+			for (j = 0; j < i; ++j)
+				free(triangle[j]);
+			free(triangle);
+			return NULL;
+		}
+		triangle[i][0] = triangle[i][i] = 1;
+		for (j = 1; j < i; ++j)
+			triangle[i][j] = triangle[i - 1][j - 1] + triangle[i - 1][j];
+	}
+
+	return triangle;
+}
+
+static void free_pascals_triangle(uint64_t **triangle)
+{
+	size_t i;
+
+	if (!triangle)
+		return;
+
+	for (i = 0; triangle[i]; ++i)
+		free(triangle[i]);
+	free(triangle);
+}
+
+static void print_pascals_triangle(FILE *file, uint64_t **triangle)
+{
+	size_t i, j;
+
+	for (i = 0; triangle[i]; ++i) {
+		for (j = 0; j < i + 1; ++j)
+			fprintf(file, "%" PRIu64 " ", triangle[i][j]);
+		fputc('\n', file);
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	uint64_t **triangle;
+	size_t num_rows;
+	char *endptr;
+
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s ROWS\n", argv[0]);
+		return 1;
+	}
+	
+	num_rows = strtoul(argv[1], &endptr, 10);
+	if (!*argv[1] || *endptr) {
+		fprintf(stderr, "ERROR: `%s' is not a valid number\n", argv[1]);
+		return 1;
+	}
+
+	triangle = create_pascals_triangle(num_rows);
+	if (!triangle) {
+		perror("ERROR: unable to create triangle");
+		return 1;
+	}
+	print_pascals_triangle(stdout, triangle);
+	free_pascals_triangle(triangle);
+	
+	return 0;
+}