scroll(1): renamed from pg(1)

I could trace strcmp(1) as far back as
<293436c5ad/src/streq.c>
in my repo.

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 rpn scrut str strcmp swab true
+all: dj false fop hru intcmp mm npc rpn scroll scrut str strcmp swab true
 
 # keep build/include until bindgen(1) has stdin support
 # https://github.com/rust-lang/rust-bindgen/issues/2703
@@ -109,18 +109,23 @@ build/bin/hru: src/hru.rs build rustlibs
 
 .PHONY: intcmp
 intcmp: build/bin/intcmp
-build/bin/intcmp: src/intcmp.c build
-	$(CC) $(CFLAGS) -o $@ src/intcmp.c
+build/bin/intcmp: src/intcmp.rs build rustlibs
+	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/intcmp.rs
 
 .PHONY: mm
 mm: build/bin/mm
-build/bin/mm: src/mm.c build
-	$(CC) $(CFLAGS) -o $@ src/mm.c
+build/bin/mm: src/mm.rs build rustlibs 
+	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/mm.rs
 
 .PHONY: npc
 npc: build/bin/npc
 build/bin/npc: src/npc.c build
-	$(CC) $(CFLAGAS) -o $@ src/npc.c
+	$(CC) $(CFLAGS) -o $@ src/npc.c
+
+.PHONY: scroll
+scroll: build/bin/scroll
+build/bin/scroll: src/scroll.c build
+	$(CC) $(CFLAGS) -o $@ src/scroll.c
 
 .PHONY: rpn
 rpn: build/bin/rpn

docs/mm.1

@@ -3,14 +3,14 @@
 .\" 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 MM 1 2024-06-17 "Harakit X.X.X"
+.TH MM 1 2024-07-14 "Harakit X.X.X"
 .SH NAME
 mm \(en middleman
 .\"
 .SH SYNOPSIS
 
 mm
-.RB [ -aenu ]
+.RB [ -aetu ]
 .RB [ -i\ input ]
 .RB [ -o\ output ]
 .\"
@@ -21,19 +21,25 @@ Catenate input files and write them to the start of each output file or stream.
 .SH OPTIONS
 
 .IP \fB-a\fP
-Opens subsequent outputs for appending rather than updating.
+Opens outputs for appending rather than updating.
 .IP \fB-e\fP
 Use the standard error as an output.
-.IP \fB-i\fP\ \fIinput\fP
-Opens a path as an input. If one or more of the input files is \(lq-\(rq or if
-no inputs are specified, the standard input shall be used.
-.IP \fB-o\fP\ \fIoutput\fP
-Opens a path as an output. If one or more of the output files is \(lq-\(rq or if
-no outputs are specified, the standard output shall be used.
+.IP \fB-t\fP
+Causes outputs to be overwritten instead of being truncated.
 .IP \fB-u\fP
 Ensures neither input or output will be buffered.
-.IP \fB-n\fP
-Causes SIGINT signals to be ignored.
+.IP \fB-i\fP\ \fIinput\fP
+Opens a path as an input. If one or more of the input files is \(lq-\(rq or if
+no inputs are specified, the standard input shall be used. If specified as the
+last option and if there are trailing arguments to the program, they shall be
+appended to the list of files to use as inputs.
+.IP \fB-o\fP\ \fIoutput\fP
+Opens a path as an output. If one or more of the output files is \(lq-\(rq or if
+no outputs are specified and the
+.B -e
+option is not specified, the standard output shall be used. If specified as the
+last option and if there are trailing arguments to the program, they shall be
+appended to the list of files to use as outputs.
 .\"
 .SH DIAGNOSTICS
 
@@ -45,10 +51,6 @@ exits with the appropriate
 .BR sysexits.h (3)
 status.
 .\"
-.SH CAVEATS
-
-Existing files are not truncated on ouput and are instead overwritten.
-.\"
 .SH RATIONALE
 
 The

docs/scroll.1

@@ -0,0 +1,52 @@
+.\" Copyright (c) 2024 DTB <trinity@trinity.moe>
+.\" Copyright (c) 2024 Emma Tebibyte <emma@tebibyte.media>
+.\"
+.\" 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 PG 1 2024-07-31 "Harakit X.X.X"
+.SH NAME
+scroll \(en present output
+.\"
+.SH SYNOPSIS
+
+scroll
+.RB ( -p
+.RB [ prompt ])
+.\"
+.SH DESCRIPTION
+
+Print standard input to standard output, accepting commands between pages.
+.\"
+.SH OPTIONS
+
+.IP -p
+Replace the default prompt (\(lq: \(rq) with the option argument.
+.\"
+.SH DIAGNOSTICS
+
+In the event of an error, a debug message will be printed and the program will
+exit with the appropriate
+.BR sysexits.h (3)
+error code.
+.\"
+.SH RATIONALE
+
+Plan 9 from Bell Labs had
+.BR p (1),
+a similar \(lqcooked\(rq-mode paginator (as opposed to \(lqraw\(rq mode, which a
+vast majority of paginators use).
+.\"
+.SH AUTHOR
+
+Written by DTB
+.MT trinity@trinity.moe
+.ME .
+.\"
+.SH COPYRIGHT
+
+Copyright \(co 2024 DTB. License AGPLv3+: GNU AGPL version 3 or later
+<https://gnu.org/licenses/agpl.html>.
+.\"
+.SH SEE ALSO
+.BR more (1p)

docs/strcmp.1

@@ -4,7 +4,7 @@
 .\" 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 STRCMP 1 2024-06-17 "Harakit X.X.X"
+.TH STRCMP 1 2024-07-15 "Harakit X.X.X"
 .SH NAME
 strcmp \(en compare strings
 .\"
@@ -20,15 +20,15 @@ Check whether string arguments are the same.
 .SH DIAGNOSTICS
 
 The program will exit successfully if the strings are identical. Otherwise, it
-will exit with an error code of 1 if a string passed has a lesser byte value
-than one of the prior strings:
+will exit with an error code less than 128 if a string passed has a lesser byte
+value than one of the prior strings:
 
 .RS
 strcmp b a
 .RE
 
-or with an error code of 255 if it has a greater byte value than one of the
-prior strings:
+or with an error code greater than 128 if it has a greater byte value than one
+of the prior strings:
 
 .RS
 strcmp a b

docs/swab.1

@@ -11,7 +11,6 @@ swab \(en swap bytes
 .SH SYNOPSIS
 
 swab
-.RB [ -f ]
 .RB [ -w\ word_size ]
 .\"
 .SH DESCRIPTION
@@ -20,8 +19,6 @@ Swap the latter and former halves of a block of bytes.
 .\"
 .SH OPTIONS
 
-.IP \fB-f\fP
-Ignore SIGINT signal.
 .IP \fB-w\fP\ \fIword_size\fP
 Configures the word size; that is, the size in bytes of the block size on which
 to operate. The default word size is 2. The word size must be cleanly divisible

src/intcmp.c

@@ -1,91 +0,0 @@
-/*
- * Copyright (c) 2023 DTB <trinity@trinity.moe>
- * Copyright (c) 2024 Emma Tebibyte <emma@tebibyte.media>
- * SPDX-License-Identifier: AGPL-3.0-or-later
- *
- * This program is free software: you can redistribute it and/or modify it under
- * the terms of the GNU Affero General Public License as published by the Free
- * Software Foundation, either version 3 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 Affero General Public License for more
- * details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program. If not, see https://www.gnu.org/licenses/.
- */
-
-#include <errno.h> /* errno */
-#include <stdio.h> /* fprintf(3), stderr */
-#include <stdlib.h> /* strtol(3), size_t, EXIT_FAILURE */
-#include <unistd.h> /* getopt(3), optind */
-#include <sysexits.h> /* EX_OK, EX_USAGE */
-
-#define /* 0b00? */    EQUAL   0x01 /* | -e  | 0b001 | 1 */
-#define /* 0b0?0 */    GREATER 0x02 /* | -g  | 0b010 | 2 */
-/*             Equal | Greater 0x03    | -ge | 0b011 | 3 */
-#define /* 0b?00 */    LESSER  0x04 /* | -l  | 0b100 | 4 */
-/*             Equal | Lesser  0x05    | -le | 0b101 | 5 */
-/* (Inequal) Greater | Lesser  0x06    | -gl | 0b110 | 6 */
-
-char *program_name = "intcmp";
-
-static int
-usage(char *argv0) {
-	(void)fprintf(stderr, "Usage: %s [-egl] integer integer...\n", argv0);
-
-	return EX_USAGE;
-}
-
-int main(int argc, char *argv[]) {
-	int c;
-	size_t i;
-	unsigned char mode;
-	int r; /* reference integer */
-	mode = 0;
-
-	if (argc < 3) {
-		return usage(argv[0] == NULL ? program_name : argv[0]);
-	}
-
-	while ((c = getopt(argc, argv, "egl")) != -1) {
-		switch (c) {
-			case 'e': mode |= EQUAL;   break;
-			case 'g': mode |= GREATER; break;
-			case 'l': mode |= LESSER;  break;
-			default:  return usage(argv[0]);
-		}
-	}
-
-	if (optind + 2 /* ref cmp */ > argc) { return usage(argv[0]); }
-
-	i = optind;
-
-	do {
-		r = c;
-		c = strtol(argv[i], &argv[i], 10);
-
-		if (*argv[i] != '\0' || errno != 0) {
-			fprintf(
-				stderr,
-				"%s: argument #%d: Invalid integer\n",
-				argv[0],
-				(int)i
-			);
-			return EX_USAGE;
-		}
-
-		if (i == optind) { continue; }
-
-		/* rule enforcement; if a mode isn't permitted and the numbers
-		 * correspond to it, return 1 */
-		if (   (!(mode & EQUAL) && r == c)
-			|| (!(mode & GREATER) && r > c)
-			|| (!(mode & LESSER) && r < c)
-		) { return 1; }
-	} while (++i < argc);
-	
-	return EX_OK;
-}

src/intcmp.rs

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2023–2024 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
+ * the terms of the GNU Affero General Public License as published by the Free
+ * Software Foundation, either version 3 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 Affero General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see https://www.gnu.org/licenses/.
+ */
+
+use std::{
+	env::args,
+	process::ExitCode
+};
+
+extern crate getopt;
+use getopt::GetOpt;
+
+extern crate sysexits;
+use sysexits::EX_USAGE;
+
+fn usage(s: &str) -> ExitCode {
+	eprintln!("Usage: {} [-egl] integer integer...", s);
+	ExitCode::from(EX_USAGE as u8)
+}
+
+fn main() -> ExitCode {
+	let argv = args().collect::<Vec<String>>();
+	let mut e = false; /* args can be == */
+	let mut g = false; /* args can be > */
+	let mut l = false; /* args can be < */
+	let mut optind = 0;
+
+	if argv.len() < 3 { return usage(&argv[0]); }
+
+	while let Some(opt) = argv.getopt("egl") {
+		match opt.opt() {
+			Ok("e") => e = true,
+			Ok("g") => g = true,
+			Ok("l") => l = true,
+			_ => { return usage(&argv[0]); },
+		}
+		optind = opt.ind();
+	}
+
+	if argv.len() - optind < 2 /* see usage */ { return usage(&argv[0]); }
+
+	let mut prev: Option<usize> = None; /* no previous operand */
+	let mut currn: usize;
+
+	for arg in argv.iter().skip(optind) { /* iterate operands */
+		match arg.parse::<usize>() { /* parse current operand */
+			Ok(n) => currn = n,
+			_ => {
+				eprintln!("{}: {}: Invalid integer", &argv[0], arg);
+				return ExitCode::from(EX_USAGE as u8);
+			}
+		}
+
+		if let Some(prevn) = prev { /* if there was a previous opr., test */
+			if (!e && prevn == currn)
+					|| (!g && prevn > currn)
+					|| (!l && prevn < currn)
+				{ return ExitCode::FAILURE; }
+		}
+
+		prev = Some(currn); /* there is a previous operand */
+	}
+
+	ExitCode::SUCCESS
+}

src/mm.c

@@ -1,242 +0,0 @@
-/*
- * Copyright (c) 2024 DTB <trinity@trinity.moe>
- * Copyright (c) 2024 Emma Tebibyte <emma@tebibyte.media>
- * SPDX-License-Identifier: AGPL-3.0-or-later
- *
- * This program is free software: you can redistribute it and/or modify it under
- * the terms of the GNU Affero General Public License as published by the Free
- * Software Foundation, either version 3 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 Affero General Public License for more
- * details.
- *
- * You should have received a copy of the GNU Affero General Public License
- * along with this program. If not, see https://www.gnu.org/licenses/.
- */
-
-#include <errno.h> /* errno */
-#include <signal.h> /* signal(2), SIG_ERR, SIG_IGN, SIGINT */
-#include <stdio.h> /* fclose(3), fopen(3), fprintf(3), getc(3), putc(3),
-                    * setvbuf(3), size_t, _IONBF, NULL */
-#include <stdlib.h> /* free(3), realloc(3) */
-#include <string.h> /* strcmp(3), strerror(3) */
-#include <unistd.h> /* getopt(3) */
-#include <sysexits.h> /* EX_IOERR, EX_OK, EX_OSERR, EX_USAGE */
-
-/* This structure is how open files are tracked. */
-struct Files{
-	size_t a;	/* allocation */
-	size_t s;	/* used size */
-	char *mode;	/* file opening mode */
-	char **names;	/* file names */
-	FILE **files;	/* file pointers */
-};
-
-/* How much to grow the allocation when it's saturated. */
-#ifndef ALLOC_INCREMENT
-#	define ALLOC_INCREMENT 1
-#endif
-
-/* How much to grow the allocation at program start. */
-#ifndef ALLOC_INITIAL
-#	define ALLOC_INITIAL 10
-#endif
-
-/* pre-allocated strings */
-char *program_name = "mm";
-static char *stdin_name = "<stdin>";
-static char *stdout_name = "<stdout>";
-static char *stderr_name = "<stderr>";
-static char *(fmode[]) = { (char []){"rb"}, (char []){"rb+"} };
-static char *wharsh = "wb";
-
-/* Adds the open FILE pointer for the file at the path s to the files struct,
- * returning the FILE if successful and NULL if not, allocating more memory in
- * the files buffers as needed. */
-static FILE *
-Files_append(struct Files *files, FILE *file, char *name) {
-
-	if (file == NULL || (files->s == files->a
-			&& ((files->files = realloc(files->files,
-					(files->a += (files->a == 0)
-						? ALLOC_INITIAL
-						: ALLOC_INCREMENT)
-					* sizeof *(files->files))) == NULL
-				|| (files->names = realloc(files->names,
-					files->a * sizeof *(files->names))) == NULL)))
-		return NULL;
-
-	files->names[files->s] = name;
-	return files->files[files->s++] = file;
-}
-
-/* Opens the file at the path p and puts it in the files struct, returning NULL
- * if either the opening or the placement of the open FILE pointer fail. */
-#define Files_open(files, p) \
-	Files_append((files), fopen((p), (files)->mode), (p))
-
-/* Prints a diagnostic message based on errno and returns an exit status
- * appropriate for an OS error. */
-static int
-oserr(char *s, char *r) {
-	(void)fprintf(stderr, "%s: %s: %s\n", s, r, strerror(errno));
-
-	return EX_OSERR;
-}
-
-static int
-usage(char *argv0) {
-	(void)fprintf(
-		stderr,
-		"Usage: %s [-aenu] [-i input]... [-o output]...\n",
-		argv0
-	);
-
-	return EX_USAGE;
-}
-
-int main(int argc, char *argv[]) {
-	struct Files files[2]; /* {read, write} */
-	int retval;
-
-	/* Initializes the files structs with their default values, standard
-	 * input and standard output. If an input or an output is specified
-	 * these initial values will be overwritten, so to, say, use mm(1)
-	 * equivalently to tee(1p), -o - will need to be specified before
-	 * additional files to ensure standard output is still written. */
-	for (size_t i = 0; i < 2; ++i) {
-		files[i].a = 0;
-		files[i].s = 0;
-		files[i].mode = fmode[i];
-		files[i].files = NULL;
-		files[i].names = NULL;
-
-		if (Files_append(
-					&files[i],
-					i == 0 ? stdin : stdout,
-					i == 0 ? stdin_name : stdout_name
-				) == NULL) {
-			return oserr(program_name, i == 0 ? stdin_name : stdout_name);
-		}
-
-		files[i].s = 0;
-	}
-
-	if (argc > 0) {
-		int c;
-		char unbuffered = 0;
-
-		program_name = argv[0];
-
-		while ((c = getopt(argc, argv, "aehi:no:u")) != -1) {
-			switch (c) {
-				case 'a': /* "rb+" -> "ab" */
-					files[1].mode[0] = 'a';
-					files[1].mode[2] = '\0';
-					break;
-				case 'e':
-					if (Files_append(&files[1], stderr, stderr_name) == NULL) {
-						return oserr(program_name, stderr_name);
-					}
-					break;
-				case 'i':
-					if (
-						(strcmp(optarg, "-") == 0
-						&& Files_append(&files[0], stdin, stdin_name) != NULL)
-						|| Files_open(&files[0], optarg) != NULL
-					) { break; }
-
-					return oserr(program_name, optarg);
-				case 'o':
-					if (
-						(strcmp(optarg, "-") == 0
-						&& Files_append(&files[1], stdout, stdout_name) != NULL)
-						|| Files_open(&files[1], optarg) != NULL
-					) { break; }
-					/* does not exist, so try to create it */
-					if (errno == ENOENT) {
-						files[1].mode = wharsh;
-
-						if (Files_open(&files[1], optarg) != NULL) {
-							files[1].mode = fmode[1];
-							break;
-						}
-					}
-
-					return oserr(program_name, optarg);
-				case 'n':
-					if (signal(SIGINT, SIG_IGN) == SIG_ERR) {
-						return oserr(program_name, "-n");
-					}
-
-					break;
-				case 'u': unbuffered = 1; break;
-				default: return usage(program_name);
-			}
-		}
-
-		if (unbuffered) { /* Unbuffer files. */
-			for (
-				size_t i = 0;
-				i < files[0].s;
-				setvbuf(files[0].files[i++], NULL, _IONBF, 0)
-			);
-			for (
-				size_t i = 0;
-				i < files[1].s;
-				setvbuf(files[1].files[i++], NULL, _IONBF, 0)
-			);
-		}
-	}
-
-	if (optind != argc) { return usage(program_name); }
-
-	files[0].s += files[0].s == 0;
-	files[1].s += files[1].s == 0;
-	
-
-	retval = EX_OK;
-
-	/* Actual program loop. */
-	for (size_t i = 0; i < files[0].s; ++i) { /* iterate ins */
-		int c;
-
-		while ((c = getc(files[0].files[i])) != EOF) { /* iterate chars */
-			for (size_t j = 0; j < files[1].s; ++j) { /* iterate outs */
-				if (putc(c, files[1].files[j]) == EOF) { /* notebook's full */
-					retval = EX_IOERR;
-					(void)fprintf(
-						stderr,
-						"%s: %s: %s\n",
-						program_name,
-						files[1].names[j],
-						strerror(errno)
-					);
-
-					if (fclose(files[1].files[j]) == EOF) {
-						(void)fprintf(
-							stderr,
-							"%s: %s: %s\n",
-							program_name,
-							files[1].names[j],
-							strerror(errno)
-						);
-					}
-
-					/* massage out the tense muscle */
-					for(size_t k = j--; k < files[1].s - 1; ++k){
-						files[1].files[k] = files[1].files[k+1];
-						files[1].names[k] = files[1].names[k+1];
-					}
-
-					if(--files[1].s == 0) { return retval; }
-				}
-			}
-		}
-	}
-
-	return retval;
-}

src/mm.rs

@@ -0,0 +1,185 @@
+/*
+ * Copyright (c) 2024 Emma Tebibyte <emma@tebibyte.media>
+ * Copyright (c) 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
+ * the terms of the GNU Affero General Public License as published by the Free
+ * Software Foundation, either version 3 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 Affero General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see https://www.gnu.org/licenses/.
+ */
+
+use std::{
+	env::args,
+	fs::File,
+	io::{ stdin, stdout, stderr, BufWriter, Read, Write },
+	os::fd::{ AsRawFd, FromRawFd },
+	process::{ exit, ExitCode },
+};
+
+extern crate getopt;
+extern crate strerror;
+extern crate sysexits;
+
+use getopt::GetOpt;
+use strerror::StrError;
+use sysexits::{ EX_IOERR, EX_USAGE };
+
+use ArgMode::*;
+
+enum ArgMode { In, Out }
+
+fn main() -> ExitCode {
+	let argv = args().collect::<Vec<_>>();
+	let usage = format!("Usage: {} [-aetu] [-i input] [-o output]", argv[0]);
+
+	let mut a = false; /* append to the file */
+	let mut e = false; /* use stderr as an output */
+	let mut t = true; /* do not truncate the file before writing */
+	let mut u = false; /* unbuffer i/o */
+	let mut ins = Vec::new(); /* initial input file path vector */
+	let mut outs = Vec::new(); /* initial output file path vector */
+	let mut mode: Option<ArgMode> = None; /* mode set by last-used option */
+	let mut optind = 0;
+
+	while let Some(opt) = argv.getopt("aei:o:tu") {
+		match opt.opt() {
+			Ok("a") => a = true,
+			Ok("e") => e = true, 
+			Ok("u") => u = true,
+			Ok("t") => t = false,
+			Ok("i") => { /* add inputs */
+				let input = opt.arg().unwrap();
+				ins.push(input);
+				mode = Some(In); /* latest argument == -i */
+			},
+			Ok("o") => { /* add output */
+				let output = opt.arg().unwrap(); 
+				outs.push(output);
+				mode = Some(Out); /* latest argument == -o */
+			},
+			Err(_) | Ok(_) => {
+				eprintln!("{}", usage);
+				return ExitCode::from(EX_USAGE as u8);
+			},
+		};
+
+		optind = opt.ind();
+	}
+
+	let remaining = argv.iter().skip(optind);
+
+	/* check the last flag specified */
+	if let Some(m) = mode {
+		for arg in remaining {
+			/* move the subsequent arguments to the list of inputs or outputs */
+			match m {
+				In => ins.push(arg.to_string()),
+				Out => outs.push(arg.to_string()),
+			};
+		}
+	} else {
+		eprintln!("{}", usage);
+		return ExitCode::from(EX_USAGE as u8);
+	}
+
+	/* use stdin if no inputs are specified */
+	if ins.is_empty() { ins.push("-".to_string()); }
+
+	/* use stdout if no outputs are specified */
+	if outs.is_empty() && !e { outs.push("-".to_string()); }
+	
+	/* map all path strings to files */
+	let inputs = ins.iter().map(|file| {
+		/* if a file is “-”, it is stdin */
+		if *file == "-" {
+			/* portable way to access stdin as a file */
+			return unsafe { File::from_raw_fd(stdin().as_raw_fd()) };
+		}
+
+		match File::open(file) {
+			Ok(f) => f,
+			Err(e) => {
+				eprintln!("{}: {}: {}", argv[0], file, e.strerror());
+				exit(EX_IOERR);
+			},
+		}
+	}).collect::<Vec<_>>();
+
+	/* map all path strings to files */
+	let mut outputs = outs.iter().map(|file| {
+		/* of a file is “-”, it is stdout */
+		if *file == "-" {
+			/* portable way to access stdout as a file */
+			return unsafe { File::from_raw_fd(stdout().as_raw_fd()) }; 
+		}
+
+		let options = File::options()
+			/* don’t truncate if -t is specified, append if -a is specified */
+			.truncate(t)
+			.append(a)
+			/* enable the ability to create and write to files */
+			.create(true)
+			.write(true)
+			/* finally, open the file! */
+			.open(file);
+
+		match options {
+			Ok(f) => return f,
+			Err(e) => {
+				eprintln!("{}: {}: {}", argv[0], file, e.strerror());
+				exit(EX_IOERR);
+			},
+		};
+	}).collect::<Vec<_>>();
+
+	/* if -e is specified, use stderr */
+	if e {
+		/* portable way to access stderr as a file */
+		outputs.push(unsafe { File::from_raw_fd(stderr().as_raw_fd()) });
+	}
+
+	let mut outputs = outputs.iter().map(|o| {
+		if u {
+			/* unbuffered writing through a buffer of capacity 0 */
+			BufWriter::with_capacity(0, o)
+		} else {
+			/* theoretically buffered writing */
+			BufWriter::new(o)
+		}
+	}).collect::<Vec<_>>();
+
+	for file in inputs {
+		for byte in file.bytes().map(|b| {
+			b.unwrap_or_else(|e| {
+				eprintln!("{}: {}", argv[0], e.strerror());
+				exit(EX_IOERR);
+			})
+		}) {
+			for out in &mut outputs {
+				if let Err(e) = out.write(&[byte]) {
+					eprintln!("{}: {}", argv[0], e.strerror());
+					return ExitCode::from(EX_IOERR as u8);
+				}
+
+				if u {
+					/* immediately flush the output for -u */
+					if let Err(e) = out.flush() { 
+						eprintln!("{}: {}", argv[0], e.strerror());
+						return ExitCode::from(EX_IOERR as u8);
+					}
+				}
+			}
+		}
+	}
+
+	ExitCode::SUCCESS
+}

src/scroll.c

@@ -0,0 +1,288 @@
+/*
+ * Copyright (c) 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
+ * the terms of the GNU Affero General Public License as published by the Free
+ * Software Foundation, either version 3 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 Affero General Public License for more
+ * details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program. If not, see https://www.gnu.org/licenses/.
+ */
+
+#include <assert.h> /* assert(3) */
+#include <errno.h> /* errno */
+#include <stdbool.h> /* bool */
+#include <stdio.h> /* fclose(3), feof(3), fgetc(3), fgets(3), fopen(3),
+                    * fprintf(3), fputc(3), perror(3), stderr, stdin, stdout,
+                    * EOF, FILE, NULL */
+#include <stdlib.h> /* size_t */
+#include <string.h> /* strchr(3), strcmp(3) */
+#include <unistd.h> /* getopt(3) */
+
+/* Commands start with cmd_. They take an argc and NULL-terminated argv, like
+ * main, and return a status from <sysexits.h>. Return values other than EX_OK
+ * and EX_USAGE cause pg(1) to exit with that value, except EX_UNAVAILABLE,
+ * which causes pg(1) to exit with the status EX_OK. */
+#include <sysexits.h>
+
+#define CMDLINE_MAX 99+1 /* Maximum length of command line. */
+
+static char *whitespace = " \n\r\t\v";
+
+//static
+struct Tube {
+	char *name;   // command line
+	FILE *in;     // process stdin
+	FILE *out;    // process stdoout
+	size_t index; // in pipeline
+};
+
+static struct {
+	size_t quantity;
+	enum { LINES = 0, BYTES = 1 } type;
+} default_page_unit = { 22, LINES } /* Plan 9 default */;
+
+static char *prompt = ": ";
+static char *program_name = "pg";
+
+static char *
+permute_out(char *s, size_t i) {
+	for (
+		;
+		s[i] != '\0';
+		s[i] = s[i + 1], ++i
+	);
+
+	return s;
+}
+
+/* strtok(3p), but supports double-quotes and escapes (but only for escaping
+ * quotes).  Unmatched quotes in str are considered literal. The behavior of
+ * strtok_quoted when '\'', '"', or '\\' are in sep is undefined. Use of UTF-8
+ * separators with strtok_quoted is undefined. */
+static char *
+strtok_quoted(char *str, char *sep) {
+	static char *s;
+
+	if (str != NULL) { s = str; }
+
+	while (strchr(sep, *s) != NULL) { // skip beginning whitespace
+		if(*++s == '\0') { return NULL; } // no remaining except seps
+	}
+
+	{
+		bool in_escape = 0; // previous char was '\\'
+		char quote = '\0';  // quotation mark used, or '\0' if none
+
+		for (int i = 0; s[i] != '\0'; ++i)
+			switch (s[i]) {
+				case '\\':
+					// if literal "\\", permute out a backslash
+					if (in_escape) { (void)permute_out(s, i--); }
+					in_escape = !in_escape;
+					break;
+				case '\'': case '"':
+					if (in_escape) { // \"
+						s[i] = s[i - 1];
+						(void)permute_out(s, i--); // permute out backslash
+					} else if (s[i] == quote) {
+						quote = '\0';
+						(void)permute_out(s, i--); // second quote
+					} else {
+						quote = s[i];
+						if (strchr(&s[i + 1], quote) != NULL) { // has a match
+							(void)permute_out(s, i--); // permute out lquote
+						}
+					}
+					break;
+				case '\0': return s;
+				default:
+					if (!in_escape
+					    	&& quote == '\0'
+					    	&& (strchr(sep, s[i]) != NULL || s[i] == '\0')) {
+						char *t; // start of current token
+
+						t = s;
+						s = s[i] != '\0'
+							? &t[i + 1] // store start of next token,
+							: &t[i];    // or the address of the nul if found
+						s[i] = '\0'; // NUL terminate current token
+
+						return t;
+					}
+			}
+	}
+
+	return s;
+}
+
+/* Page at most l bytes from f without consideration of a buffer (print them to
+ * stdout). */
+static int
+pg_b_u(FILE *f, size_t l) {
+	int c;
+
+	while ((c = fgetc(f)) != EOF) {
+		if ((c = fputc(c, stdout)) == EOF || --l == 0) { break; }
+	}
+
+	return c;
+}
+
+/* Page at most l lines, which are lengths of characters terminated by nl, from
+ * f without consideration of a buffer (print them to stdout). */
+static int
+pg_l_u(FILE *f, size_t l, char nl) {
+	int c;
+
+	while ((c = fgetc(f)) != EOF) {
+		if ((c = fputc(c, stdout)) == EOF || (l -= (c == nl)) == 0) { break; }
+	}
+
+	return c;
+}
+
+static int
+cmd_quit(int argc, char **argv, char **envp) { return EX_UNAVAILABLE; }
+
+static int
+cmd_default_page(int argc, char **argv, char **envp) {
+	if (argc > 1) { return EX_USAGE; } // should be impossible
+	else if (default_page_unit.type == BYTES) {
+		return pg_b_u(stdin, default_page_unit.quantity) == EOF
+			? EX_UNAVAILABLE
+			: EX_OK;
+	} else if (default_page_unit.type == LINES) {
+		return pg_l_u(stdin, default_page_unit.quantity, '\n') == EOF
+			? EX_UNAVAILABLE
+			: EX_OK;
+	} else { return EX_SOFTWARE; }
+}
+
+static int
+cmd_page_down_lines(int argc, char **argv, char **envp) {
+	switch (argc) {
+		case 1: return cmd_default_page(argc, argv, envp);
+		case 2: /* not implemented */
+		default:
+			(void)fprintf(stderr, "Usage: %s" /*" (lines)"*/ "\n", argv[0]);
+			return EX_USAGE;
+	}
+}
+
+/* A CmdMap must be NULL-terminated. */
+static struct CmdMap{ char *name; int (*fn)(int, char **, char **); }
+builtins[] = {
+	/* don't make the user feel trapped */
+	{ ":q", cmd_quit }, { ":q!", cmd_quit },
+	{ "exit", cmd_quit }, { "q", cmd_quit }, { "Q", cmd_quit },
+	{ "quit", cmd_quit }, { "ZZ", cmd_quit },
+	
+	{ NULL, NULL }
+};
+
+#define ARGV_MAX 10
+/* Find and execute the command in the command map, given a corresponding
+ * command line. */
+static int
+cmdline_exec(struct CmdMap *map, char *cmdline, char **envp) {
+	static int argc;
+	static char *argv[ARGV_MAX];
+
+	if ((argv[(argc = 0)] = strtok_quoted(cmdline, whitespace)) == NULL) {
+		while (cmdline[0] != '\0') { cmdline = &cmdline[1]; }
+		argv[argc] = cmdline;
+		argv[++argc] = NULL;
+	} else {
+		while (
+			(argv[++argc] = strtok_quoted(NULL, whitespace)) != NULL
+			&& argc < ARGV_MAX
+		);
+	}
+
+	for (; map->name != NULL; map = &map[1]) {
+		if(strcmp(map->name, argv[0]) == 0) {
+			return map->fn(argc, argv, envp);
+		}
+	}
+
+	(void)fprintf(stderr, "%s: %s: not found\n", program_name, argv[0]);
+	return EX_USAGE;
+}
+
+static int
+ioerr(char *argv0) {
+	perror(argv0);
+
+	return EX_IOERR;
+}
+
+static int
+usage(char *argv0) {
+	(void)fprintf(stderr, "Usage: %s [-p prompt]\n", argv0);
+
+	return EX_USAGE;
+}
+
+int main(int argc, char *argv[]) {
+	unsigned char cmd[CMDLINE_MAX];
+	FILE *t;
+
+	if (argc > 0) {
+		int c;
+
+		program_name = argv[0];
+
+		while ((c = getopt(argc, argv, "p:")) != -1) {
+			switch (c) {
+				case 'p': prompt = optarg; break;
+				default:  return usage(program_name);
+			}
+		}
+	}
+
+	if (argc > optind) { return usage(program_name); }
+
+
+	if ((t = fopen("/dev/tty", "rb")) == NULL) {
+		perror(program_name);
+
+		return EX_OSERR;
+	}
+
+	for (;;) {
+		if (fputs(prompt, stderr) == EOF) { return ioerr(program_name); }
+
+		// if the line...
+		if (fgets((char *)cmd, (sizeof cmd) / (sizeof *cmd), t) != NULL) {
+			if (strchr((char *)cmd, '\n') == NULL) { // was taken incompletely
+				int c;
+
+				while ((c = fgetc(t)) != '\n') { // ...fast-forward stream
+					if (c == EOF) { break; }
+				}
+			}
+		} else { fputc('\n', stdout); } // EOF at start of line; finish prompt
+
+		if (feof(t)) { return EX_OK; }
+
+		{
+			int r;
+
+			switch ((r = cmdline_exec(builtins, (char *)cmd, NULL))){
+				case EX_OK: case EX_USAGE: break;
+				case EX_UNAVAILABLE: return EX_OK;
+				default: return r;
+			}
+		}
+	}
+
+	/* UNREACHABLE */ assert(0);
+}

src/strcmp.c

@@ -16,7 +16,6 @@
  * You should have received a copy of the GNU Affero General Public License
  * along with this program. If not, see https://www.gnu.org/licenses/.
  */
-
 #include <stdio.h> /* fprintf(3), stderr */
 #include <sysexits.h> /* EX_OK, EX_USAGE */
 

src/swab.rs

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2024 DTB <trinity@trinity.moe>
+ * Copyright (c) 2024 Emma Tebibyte <emma@tebibyte.media>
  * SPDX-License-Identifier: AGPL-3.0-or-later
  *
  * This program is free software: you can redistribute it and/or modify it under
@@ -18,7 +19,7 @@
 
 use std::{
 	env::args,
-	io::{ stdin, stdout, Error, ErrorKind, Read, Write },
+	io::{ stdin, stdout, Error, Read, Write },
 	process::ExitCode,
 	vec::Vec
 };
@@ -28,13 +29,21 @@ extern crate sysexits;
 extern crate strerror;
 
 use getopt::GetOpt;
-use sysexits::{ EX_IOERR, EX_OK, EX_USAGE };
+use sysexits::{ EX_IOERR, EX_OK, EX_OSERR, EX_USAGE };
 use strerror::StrError;
 
-fn err(s: &str, e: Error) { eprintln!("{}: {}", s, e.strerror()); }
+fn oserr(argv0: &str, e: Error) -> ExitCode {
+	eprintln!("{}: {}", argv0, e.strerror());
+	ExitCode::from(EX_OSERR as u8)
+}
+
+fn ioerr(argv0: &str, e: Error) -> ExitCode {
+	eprintln!("{}: {}", argv0, e.strerror());
+	ExitCode::from(EX_IOERR as u8)
+}
 
 fn usage(s: &str) -> ExitCode {
-	eprintln!("Usage: {} [-f] [-w word_size]", s);
+	eprintln!("Usage: {} [-w word_size]", s);
 	ExitCode::from(EX_USAGE as u8)
 }
 
@@ -43,26 +52,26 @@ fn main() -> ExitCode {
 	let mut buf: Vec<u8> = Vec::new(); // holds the sequence getting swabbed
 	let mut input = stdin();
 	let mut output = stdout().lock();
-
-	let mut force = false;
+	let mut optind: usize = 1;   // argv[0]
 	let mut wordsize: usize = 2; // default; mimics dd(1p) conv=swab
 
-	while let Some(opt) = argv.getopt("fw:") {
+	while let Some(opt) = argv.getopt("w:") {
 		match opt.opt() {
-			Ok("f") => force = true,
-			Ok("w") => { // sets new sequence length
-				if let Some(arg) = opt.arg() {
-					match arg.parse::<usize>() {
-						// an odd sequence length is nonsensical
-						Ok(w) if w % 2 == 0 => { wordsize = w; () },
+			Ok("w") => {
+					match opt.arg().unwrap().parse::<usize>() {
+						Ok(w) if w % 2 == 0 => { wordsize = w; },
 						_ => { return usage(&argv[0]); },
 					}
-				}
+				optind = opt.ind();
 			},
 			_ => { return usage(&argv[0]); }
 		}
 	}
 
+	if optind < argv.len() {
+		return usage(&argv[0]);
+	}
+
 	buf.resize(wordsize, 0);
 
 	loop {
@@ -73,22 +82,16 @@ fn main() -> ExitCode {
 
 				if let Err(e) = output.write(&right)
 						.and_then(|_| output.write(&left)) {
-					err(&argv[0], e);
-					break ExitCode::from(EX_IOERR as u8) // write error
+					break ioerr(&argv[0], e);
 				}
 
 			},
 			Ok(v) => { // partial read; partially write
 				if let Err(e) = output.write(&buf[..v]) {
-					err(&argv[0], e);
-					break ExitCode::from(EX_IOERR as u8) // write error
+					break ioerr(&argv[0], e);
 				}
 			},
-			Err(e) if e.kind() == ErrorKind::Interrupted && force => continue,
-			Err(e) => {
-				err(&argv[0], e);
-				break ExitCode::from(EX_IOERR as u8) // read error (or signal)
-			}
+			Err(e) => break oserr(&argv[0], e)
 		}
 	}
 }