Makefile: add simexec(1)

Makefile

@@ -32,7 +32,7 @@ RUSTLIBS = --extern getopt=build/o/libgetopt.rlib \
 CFLAGS += -I$(SYSEXITS)
 
 .PHONY: all
-all: argued dj false fop hru intcmp mm npc rpn scrut str strcmp swab true
+all: dj false fop hru intcmp mm npc rpn simexec scrut str strcmp swab true
 
 # keep build/include until bindgen(1) has stdin support
 # https://github.com/rust-lang/rust-bindgen/issues/2703
@@ -87,11 +87,6 @@ build/o/libsysexits.rlib: build/include/sysexits.h
 build/include/sysexits.h: build $(SYSEXITS)sysexits.h
 	printf '\043define EXIT_FAILURE 1\n' | cat - $(SYSEXITS)sysexits.h > $@
 
-.PHONY: argued
-argued: build/bin/argued
-build/bin/argued: src/argued.rs build
-	$(RUSTC) $(RUSTFLAGS) -o $@ src/argued.rs
-
 .PHONY: dj
 dj: build/bin/dj
 build/bin/dj: src/dj.c build
@@ -137,6 +132,11 @@ scrut: build/bin/scrut
 build/bin/scrut: src/scrut.c build
 	$(CC) $(CFLAGS) -o $@ src/scrut.c
 
+.PHONY: simexec
+simexec: build/bin/simexec
+build/bin/simexec: src/simexec.c build
+	$(CC) $(CFLAGS) -o $@ src/simexec.c
+
 .PHONY: str
 str: build/bin/str
 build/bin/str: src/str.c build

docs/argued.1

@@ -1,28 +0,0 @@
-.\" Copyright (c) 2022–2024 DTB <trinity@trinity.moe>
-.\"
-.\" This work is licensed under CC BY-SA 4.0. To see a copy of this license,
-.\" visit <http://creativecommons.org/licenses/by-sa/4.0/>.
-.\"
-.TH ARGUED 1 2024-07-23 "Harakit-overgrown X.X.X"
-.SH NAME
-argued \(en check for arguments
-.\"
-.SH DESCRIPTION
-
-.BR argued (1)
-exits successfully if any arguments are provided, and unsuccessfully
-otherwise.
-.\"
-.SH AUTHOR
-
-Written by DTB
-.MT trinity@trinity.moe
-.ME .
-.\"
-.SH COPYRIGHT
-
-This work is marked with CC0 1.0. To see a copy of this license, visit
-<http://creativecommons.org/publicdomain/zero/1.0>.
-.\"
-.SH SEE ALSO
-.BR test (1)

docs/simexec.1

@@ -0,0 +1,79 @@
+.\" Copyright (c) 2022–2024 DTB <trinity@trinity.moe>
+.\"
+.\" This work is licensed under CC BY-SA 4.0. To see a copy of this license,
+.\" visit <http://creativecommons.org/licenses/by-sa/4.0/>.
+.\"
+.TH SIMEXEC 1 2024-07-23 "Harakit-overgrown X.X.X"
+.SH NAME
+simexec \(en execute a program with argv
+.\"
+.SH SYNOPSIS
+
+simexec
+.B binary argv...
+.SH DESCRIPTION
+Execute a binary with a certain argv.
+.SH CAVEATS
+
+Non-binary programs cannot be executed on their own. The PATH environment
+variable is not used and a valid pathname (relative or absolute) must be
+specified.
+
+.BR simexec (1)
+requires caution.
+.B argv
+are not just the operands for the binary but in fact the direct
+.B argv
+it will receive in runtime;
+the first argv entry is the program\(cqs name, and omitting this, though valid
+use of
+.BR simexec (1),
+can break false assumptions made by programmers.
+for example, the
+.BR true (1)
+implementation in the GNU coreutils project suffers a segmentation fault it is
+given no argv[0].
+
+While POSIX.1-2017 doesn't mandate there being an argv[0] per se, a Strictly
+Conforming POSIX Application must pass an argv[0]. It has also been said that
+those who do not pass an argv[0] are mean and nasty and smell of elderberries.
+
+.BR simexec (1)
+directly uses the
+.BR execv (3p)
+library function. It cannot execute shell scripts intelligently (via shebang).
+It is inadviseable to use
+.BR simexec (1)
+to simply execute a program when other methods would suffice.
+.\"
+.SH DIAGNOSTICS
+
+.BR simexec (1)
+exits with the returned value of
+.BR execv (3p),
+which will be 255 if an error occurs in execution, such as the binary not being
+found.
+This is indistinguishable from the executed binary exiting with the same
+status.
+
+Simexec will print a error message and return the proper
+.BR sysexits.h (3)
+value if invoked in an invalid manner.
+.\"
+.SH AUTHOR
+
+Written by DTB
+.MT trinity@trinity.moe
+.ME .
+.\"
+.SH COPYRIGHT
+.\"
+Copyright \(co 2022–2024 DTB. License AGPLv3+: GNU AGPL version 3 or later
+<https://gnu.org/licenses/gpl.html>.
+.\"
+.SH SEE ALSO
+.BR execv (3p)
+
+The C89 standard's draft, section 2.1.2.2: "Hosted environment".
+
+POSIX.1-2017 System Interfaces: execv. Particularly under the RATIONALE section header.

src/simexec.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022_2024 DTB <trinity@trinity.moe>
+ * Copyright (c) 2022–2024 DTB <trinity@trinity.moe>
  * SPDX-License-Identifier: AGPL-3.0-or-later
  *
  * This program is free software: you can redistribute it and/or modify it under
@@ -16,13 +16,19 @@
  * along with this program. If not, see https://www.gnu.org/licenses/.
  */
 
- use std::{ env::args, process::ExitCode };
+#include <stdio.h> /* fprintf(3), NULL */
+#include <unistd.h> /* execv(3), */
+#include <sysexits.h> /* EX_USAGE */
 
- fn main() -> ExitCode {
+char *program_name = "simexec";
- 	let argv = args().collect::<Vec<String>>();
 
- 	match argv.len() {
+int main(int argc, char *argv[]){
- 		0 | 1 => ExitCode::FAILURE,
+	if (argc < 2) {
- 		_ =>     ExitCode::SUCCESS
+		fprintf(stderr, "Usage: %s binary argv...\n",
- 	}
+			argv[0] == NULL ? program_name : argv[0]
- }
+		);
+		return EX_USAGE;
+	}
+
+	execv(argv[1], &argv[2]);
+}