simexec(1): import from trinity/src

Makefile

@@ -32,7 +32,7 @@ RUSTLIBS = --extern getopt=build/o/libgetopt.rlib \
 CFLAGS += -I$(SYSEXITS)
 
 .PHONY: all
-all: dj false fop hru intcmp mm npc retval rpn scrut str strcmp swab true
+all: dj false fop hru intcmp mm npc rpn scrut str strcmp swab true
 
 # keep build/include until bindgen(1) has stdin support
 # https://github.com/rust-lang/rust-bindgen/issues/2703
@@ -122,11 +122,6 @@ npc: build/bin/npc
 build/bin/npc: src/npc.c build
 	$(CC) $(CFLAGAS) -o $@ src/npc.c
 
-.PHONY: retval
-retval: build/bin/retval
-build/bin/retval: src/retval.rs build rustlibs
-	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/retval.rs
-
 .PHONY: rpn
 rpn: build/bin/rpn
 build/bin/rpn: src/rpn.rs build rustlibs

docs/simexec.1

@@ -0,0 +1,49 @@
+.TH SIMEXEC 1
+
+.SH NAME
+
+simexec \(en execute a program with the given argv
+
+.SH SYNOPSIS
+
+simexec
+.RB [ pathname ]
+.RB [ argv... ]
+
+.SH DESCRIPTION
+
+Simexec executes a given program with the given argv.
+
+.SH PITFALLS
+
+Non-binary programs cannot be executed. The PATH environment variable is not used and a valid pathname (relative or absolute) must be specified.
+.PP
+Simexec relies on the user to take proper precautions.
+argv is not just the operands for the program but in fact directly the argv it will receive in runtime;
+the first argv entry is the program's name, and forgoing this, though acceptable by simexec, can break customary assumptions.
+for example, the true(1) implementation in the GNU coreutils suffers a segmentation fault if there is no argv[0].
+.PP
+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.
+.PP
+Simexec directly uses the execv library function. It cannot execute shell scripts intelligently (via shebang).
+It is inadviseable to use simexec as an alternative to simply calling a program, and in fact probably inadviseable to use simexec at all.
+
+.SH DIAGNOSTICS
+
+Simexec returns the value of execv(3), which will be -1 (or 0xFF; 255) if an error occurs.
+This is not distinguishable from the executed program returning the same exit status.
+.PP
+Simexec will print a error message and return the proper sysexits(3) value if used in an invalid manner.
+
+.SH COPYRIGHT
+
+Public domain.
+
+.SH SEE ALSO
+
+exec(3)
+.PP
+The C89 standard's draft, section 2.1.2.2: "Hosted environment".
+.PP
+POSIX.1-2017 System Interfaces: execv. Particularly under the RATIONALE section header.

src/simexec.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2024 DTB <trinity@trinity.moe>
+ * Copyright (c) 2023 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
@@ -16,24 +16,20 @@
  * 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 */
 
-extern crate sysexits;
-use sysexits::EX_USAGE;
+char *program_name = "simexec";
 
-fn usage(s: &str) -> ExitCode {
-	eprintln!("Usage: {} status", s);
-	ExitCode::from(EX_USAGE)
-}
+int main(int argc, char *argv[]){
 
-fn main() -> ExitCode {
-	let argv = args().collect::<Vec<String>>();
-
-	match argv.len() {
-		2 => match argv[1].parse::<u8>() {
-				Ok(e) => ExitCode::from(e),
-				_ => usage(&argv[0])
-			},
-		_ => usage(&argv[0])
+	if(argc < 2){
+		fprintf(stderr, "Usage: %s binary argv...\n",
+			argv[0] == NULL ? program_name : argv[0]
+		);
+		return EX_USAGE;
 	}
+
+	execv(argv[1], &argv[2]);
 }