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fb65d1f950
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b5cd33bfe6
7
Makefile
7
Makefile
@ -32,7 +32,7 @@ RUSTLIBS = --extern getopt=build/o/libgetopt.rlib \
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CFLAGS += -I$(SYSEXITS)
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.PHONY: all
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all: dj false fop hru intcmp mm npc rpn simexec scrut str strcmp swab true
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all: dj false fop hru intcmp mm npc rpn scrut str strcmp swab true
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# keep build/include until bindgen(1) has stdin support
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# https://github.com/rust-lang/rust-bindgen/issues/2703
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@ -132,11 +132,6 @@ scrut: build/bin/scrut
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build/bin/scrut: src/scrut.c build
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$(CC) $(CFLAGS) -o $@ src/scrut.c
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.PHONY: simexec
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simexec: build/bin/simexec
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build/bin/simexec: src/simexec.c build
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$(CC) $(CFLAGS) -o $@ src/simexec.c
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.PHONY: str
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str: build/bin/str
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build/bin/str: src/str.c build
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@ -1,79 +1,49 @@
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.\" Copyright (c) 2022–2024 DTB <trinity@trinity.moe>
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.\"
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.\" This work is licensed under CC BY-SA 4.0. To see a copy of this license,
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.\" visit <http://creativecommons.org/licenses/by-sa/4.0/>.
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.\"
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.TH SIMEXEC 1 2024-07-23 "Harakit-overgrown X.X.X"
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.TH SIMEXEC 1
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.SH NAME
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simexec \(en execute a program with argv
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.\"
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simexec \(en execute a program with the given argv
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.SH SYNOPSIS
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simexec
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.B binary argv...
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.RB [ pathname ]
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.RB [ argv... ]
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.SH DESCRIPTION
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Execute a binary with a certain argv.
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.SH CAVEATS
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Non-binary programs cannot be executed on their own. The PATH environment
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variable is not used and a valid pathname (relative or absolute) must be
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specified.
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Simexec executes a given program with the given argv.
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.BR simexec (1)
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requires caution.
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.B argv
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are not just the operands for the binary but in fact the direct
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.B argv
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it will receive in runtime;
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the first argv entry is the program\(cqs name, and omitting this, though valid
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use of
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.BR simexec (1),
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can break false assumptions made by programmers.
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for example, the
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.BR true (1)
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implementation in the GNU coreutils project suffers a segmentation fault it is
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given no argv[0].
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.SH PITFALLS
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While POSIX.1-2017 doesn't mandate there being an argv[0] per se, a Strictly
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Conforming POSIX Application must pass an argv[0]. It has also been said that
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those who do not pass an argv[0] are mean and nasty and smell of elderberries.
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Non-binary programs cannot be executed. The PATH environment variable is not used and a valid pathname (relative or absolute) must be specified.
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.PP
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Simexec relies on the user to take proper precautions.
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argv is not just the operands for the program but in fact directly the argv it will receive in runtime;
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the first argv entry is the program's name, and forgoing this, though acceptable by simexec, can break customary assumptions.
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for example, the true(1) implementation in the GNU coreutils suffers a segmentation fault if there is no argv[0].
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.PP
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While POSIX.1-2017 doesn't mandate there being an argv[0] per se a Strictly Conforming POSIX Application must pass an argv[0].
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It has also been said that those who do not pass an argv[0] are mean and nasty and smell of elderberries.
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.PP
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Simexec directly uses the execv library function. It cannot execute shell scripts intelligently (via shebang).
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It is inadviseable to use simexec as an alternative to simply calling a program, and in fact probably inadviseable to use simexec at all.
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.BR simexec (1)
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directly uses the
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.BR execv (3p)
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library function. It cannot execute shell scripts intelligently (via shebang).
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It is inadviseable to use
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.BR simexec (1)
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to simply execute a program when other methods would suffice.
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.\"
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.SH DIAGNOSTICS
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.BR simexec (1)
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exits with the returned value of
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.BR execv (3p),
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which will be 255 if an error occurs in execution, such as the binary not being
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found.
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This is indistinguishable from the executed binary exiting with the same
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status.
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Simexec returns the value of execv(3), which will be -1 (or 0xFF; 255) if an error occurs.
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This is not distinguishable from the executed program returning the same exit status.
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.PP
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Simexec will print a error message and return the proper sysexits(3) value if used in an invalid manner.
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Simexec will print a error message and return the proper
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.BR sysexits.h (3)
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value if invoked in an invalid manner.
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.\"
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.SH AUTHOR
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Written by DTB
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.MT trinity@trinity.moe
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.ME .
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.\"
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.SH COPYRIGHT
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.\"
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Copyright \(co 2022–2024 DTB. License AGPLv3+: GNU AGPL version 3 or later
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<https://gnu.org/licenses/gpl.html>.
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.\"
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Public domain.
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.SH SEE ALSO
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.BR execv (3p)
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exec(3)
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.PP
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The C89 standard's draft, section 2.1.2.2: "Hosted environment".
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.PP
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POSIX.1-2017 System Interfaces: execv. Particularly under the RATIONALE section header.
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@ -1,5 +1,5 @@
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/*
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* Copyright (c) 2022–2024 DTB <trinity@trinity.moe>
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* Copyright (c) 2023 DTB <trinity@trinity.moe>
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*
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* This program is free software: you can redistribute it and/or modify it under
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@ -23,7 +23,8 @@
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char *program_name = "simexec";
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int main(int argc, char *argv[]){
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if (argc < 2) {
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if(argc < 2){
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fprintf(stderr, "Usage: %s binary argv...\n",
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argv[0] == NULL ? program_name : argv[0]
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);
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