fop(1), fop.1: update to use libdelimit

CONTRIBUTING

@@ -99,17 +99,247 @@ notice:
 Style
 =====
 
-Make sure lines never exceed 80 columns in width when using four-character
-indentation steps. This helps contributors with smaller screens, those using
-side-by-side editor windows or panes, and those who have no text wrapping in
-their editor or terminal.
+“Everyone knows that debugging is twice as hard as writing a program in the
+first place. So if you’re as clever as you can be when you write it, how
+will you ever debug it?”
+	– Brian Kernighan, The Elements of Programming Style
 
-For usage text and help messages, do not implement a -h option. Instead, print
-usage information when any erroneous option is specified. Follow the NetBSD
-style guide for the usage text’s output format [0].
+The following guidelines are conducive to clear and readable code that is
+consistent with the style of the rest of the Bonsai Computer System.
+
+Use:
+
+ 0. A single line for control flow statements short enough to be easily
+ understood at a glance:
+
+	if !(argc < 0) { usage(program_name); }
+
+ This applies to C switch statements and cases and Rust match statements, as
+ well:
+
+	switch (value) { /* aligning stuff to make it easier to read is fine */
+		case possibility: variable = foo;  break;
+		default:          variable = NULL; break;
+	}
+
+ 1. Switch cases in C and match arms in Rust should start another level of
+ indentation:
+
+	switch (value) {
+		case possibility:
+			statement;
+			break;
+		default:
+			statement;
+			break;
+	}
+
+	match result {
+		Ok(n) => variable = n,
+		Err(e) => error = e,
+	}
+
+ 2. Braces in control flow where their inclusion is left optional in C:
+
+	if (condition) { statement; }
+
+ 3. Empty lines between different kinds of statements:
+
+	int t;
+
+	assert(io->bufuse > 0);
+	assert(io->bufuse <= io->bs);
+
+	if ((t = write(io->fd, io->buf, io->bufuse)) < 0) {
+		io->error = errno;
+		t = 0;
+	} else if (t > 0) {
+		memmove(io->buf, &(io->buf)[t], (io->bufuse -= t));
+	}
+
+	io->bytes += t;
+	io->prec  += (t > 0 && io->bufuse > 0);
+	io->rec   += (t > 0 && io->bufuse == 0);
+
+	return io;
+
+ 4. Compiler options that yield the most useful warnings, such as -Wpedantic in
+ a lot of C compilers. Fix the warnings, too [0].
+
+ 5. One more level of indentation and one argument per line when a function
+ call or statement header is too long to fit on one line:
+	let usage = format!(
+		"Usage: {} [-d delimiter] index command [args...]",
+		argv[0],
+	);
+
+ 6. One more level of indentation than the keyword that initiated a multi-line
+ block.
+
+	if (condition) {
+		statement;
+		statement;
+	}
+
+ 7. The return value of all non-void functions, or explicitly ignore them (like
+ casting to void in C) [0]:
+
+	if ((a = malloc(sizeof char)) == NULL) {          /* handle this error */
+		(void)fprintf(stderr, "oh noes!");   /* explicitly ignore this one */
+		return EX_OSERR;       /* ...because the program is exiting anyway */
+	}
+
+ 8. The smallest possible scope for data [0].
+
+ 9. Comments noting all the symbols and macros used from a C header file, next
+ to its include macro:
+
+	#include <unistd.h> /* close(2), getopt(3), lseek(2), read(2), write(2),
+	(space-aligned)      * optarg, optind, STDIN_FILENO, STDOUT_FILENO */
+
+ 10. Spaces in control flow statements, after the keyword and before the
+ opening brace:
+
+	for (i = 2; i < argc; ++i) {
+
+
+ 11. In Rust, a trailing comma on all arguments or fields that are on their own
+ lines:
+
+	return Err(EvaluationError {
+		message: format!("{}: Invalid token", i),
+		code: EX_DATAERR,
+	})
+
+ 12. In Rust, place extern statements after use statements that include standard
+ library crates. Group like statements:
+
+	use std::fs::Path;
+
+	extern crate strerror;
+	extern crate sysexits;
+
+	use strerror::StrError;
+	use sysexits::{ EX_OSERR, EX_USAGE };
+
+ 13. If text is on the same line as a brace, spaces after an opening brace and
+ before a closing one:
+
+	use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
+
+ 14. Alphabetic sorting, where applicable:
+
+	use std::io::{ BufWriter, Read, Write, stderr, stdin, stdout }
+
+ 15. In Rust, use the to_owned() method on string types (str, OsStr, CStr, etc.)
+ and the to_string() method on other types.
+
+
+Avoid:
+
+ 16. Unbounded loops [0].
+
+ 17. Function pointers [0].
+
+ 18. Heap memory allocation [0].
+
+ 19. Using too much nested logic (within reason).
+
+ 20. Too many levels of dereferences [0]:
+
+	/* do not do this */
+	for (size_t i = 0; i < sizeof a / sizeof *a; ++i) {
+		if (a[i].id == MATCH) { a[i].val = 0; }
+	}
+
+	/* do this */
+	for (struct MadeUp *s = &a[0]; *s != NULL; s = &s[1]) {
+		if (s->id == MATCH) { s->val = 0; }
+	}
+
+ 21. Using C preprocessor macros; the fewer, the better [0].
+
+ 22. The exit(3p) and std::process::exit() functions; returning from the main
+ function skips a system call.
+
+
+Do not use:
+
+ 23. More than the length of one printed page for a function [0].
+
+ 24. Recursion, as it’s complex and can unexpectedly overflow the stack [0].
+
+ 25. Any functionality not in the POSIX C specification and language features not
+ in C99.
+
+ 26. Do-while loops, as they’re unique to C and confusing for casual programmers.
+
+ 27. Labels and goto statements; use sensible flow control [0].
+
+ 28. Pointer arithmetic, as it tends to be confusing and unnecessary; use
+ index-reference patterns like &p[1] instead of p + 1. &p[n] is the address at
+ p + sizeof p * n, not p + n, like pointer arithmetic suggests.
+
+ 29. C struct bitfields in unions, to access certain bits of bigger data types,
+ as it’s poorly defined in the C standards; use bit arithmetic.
+
+ 30. C trigraphs.
+
+ 31. Inclusions in C header files, to prevent multiple file inclusions.
+
+ 32. C preprocessor variables to prevent multiple inclusions of the same file,
+ such as:
+
+	#ifdef _FILE
+	#define _FILE
+	/* file body */
+	#endif /* ifdef _FILE */
+
+ Instead, take the time to ensure other files aren’t including any files twice.
+
+ 33. The gets(3p) function from <stdio.h>, as it’s impossible to prevent buffer
+ overflows when it's used; use fgets(3p) from <stdio.h>.
+
+ 34. The scanf(3p) function from <stdio.h> [1].
+
+ 35. Any functionality not described in the latest POSIX make(1) specification.
+
+ 36. Macros which panic on failure in Rust (such as the print!() and println!()
+ macros). Use a function and handle any errors. However, do use the eprintln!()
+ macro for error messages. Handling an error for writing an error message is
+ redundant.
+
+ 37. A -h option for help text. Instead, print usage information when any
+ erroneous option is specified. See the Usage Text section below.
+
+ 38. Lines which exceed 80 columns in width when using four-column indentation
+ steps. This helps contributors with smaller screens, those using side-by-side
+ editor windows or panes, and those who have no text wrapping in their editor or
+ terminal.
+
+
+Usage Text
+==========
+
+This section is adapted from the NetBSD style guide [2].
+
+When programs are invoked incorrectly and in the synopsis of manual pages, uasge
+text should be provided to the user. The following is the format used by this
+project for this purpose:
+
+All optional arguments are to be placed in square brackets (U+005B, U+005D).
+Mutually exclusive arguments can be separated by a vertical line (U+007C).
+Groups of arguments should be specified in alphabetical order in most cases. The
+order of arguments and an example of these rules follows:
+
+ 0. Options with no option arguments.
+ 1. Options with option arguments. Arguments should be specified inside the same
+ square brackets as the options.
+ 3. Non-option arguments.
+
+	"usage: f [-aDde] [-b b_arg] [-m m_arg] req1 req2 [opt1 [opt2]]\n"
+	"usage: f [-a | -b] [-c [-de] [-n number]]\n"
 
-If committing a new utility, please include tests and documentation (see
-tests/ and docs/) for the new tool.
 
 Committing
 ==========
@@ -117,6 +347,10 @@ Committing
 When contributing to Bonsai, please sign your commit with a PGP key and create
 the commit with an identity which can be easily contacted.
 
+If committing a new utility, please include tests and documentation (see
+tests/ and docs/) for the new tool.
+
+
 Format commit messages following these guidelines:
 
 $ git commit -m 'tool(1): add feature x'
@@ -147,9 +381,16 @@ Commit messages should be written in the present tense.
 References
 ==========
 
-[0] <http://cvsweb.netbsd.org/bsdweb.cgi/~checkout~/src/share/misc/style>
+[0] <https://web.eecs.umich.edu/~imarkov/10rules.pdf>
+[1] <http://sekrit.de/webdocs/c/beginners-guide-away-from-scanf.html>
+[2] <http://cvsweb.netbsd.org/bsdweb.cgi/~checkout~/src/share/misc/style>
 
 
 --
-This work © 2023–2024 by Emma Tebibyte is licensed under CC BY-SA 4.0. To view a
-copy of this license, visit <http://creativecommons.org/licenses/by-sa/4.0/>
+
+Copyright © 2023–2024 Emma Tebibyte <emma@tebibyte.media>
+Copyright © 2024 DTB <trinity@trinity.moe>
+Copyright © Wikipedia contributors
+
+This work is licensed under CC BY-SA 4.0. To view a copy of this license, visit
+<http://creativecommons.org/licenses/by-sa/4.0/>.

Makefile

@@ -30,7 +30,8 @@ SYSEXITS != printf '\043include <sysexits.h>\n' | cpp -M - | tr ' ' '\n' \
 
 CC ?= cc
 RUSTC ?= rustc
-RUSTFLAGS += --extern getopt=build/o/libgetopt.rlib \
+RUSTFLAGS += --extern delimit=build/o/libdelimit.rlib \
+	--extern getopt=build/o/libgetopt.rlib \
 	--extern strerror=build/o/libstrerror.rlib \
 	--extern sysexits=build/o/libsysexits.rlib
 CFLAGS += -I$(SYSEXITS)
@@ -88,8 +89,12 @@ docs: docs/ build
 include $(OS_INCLUDE)
 
 .PHONY: rustlibs
-rustlibs: build/o/libgetopt.rlib build/o/libstrerror.rlib \
-	 build/o/libsysexits.rlib $(OSLIB)
+rustlibs: build/o/libdelimit.rlib build/o/libgetopt.rlib \
+	 build/o/libstrerror.rlib build/o/libsysexits.rlib $(OSLIB)
+
+build/o/libdelimit.rlib: build src/libdelimit.rs
+	$(RUSTC) $(RUSTFLAGS) --crate-type=lib --crate-name=delimit \
+		-o $@ src/libdelimit.rs
 
 build/o/libgetopt.rlib: build src/libgetopt.rs
 	$(RUSTC) $(RUSTFLAGS) --crate-type=lib --crate-name=getopt \
@@ -120,7 +125,7 @@ build/bin/false: src/false.c build
 .PHONY: fileis
 fileis: build/bin/fileis
 build/bin/fileis: src/fileis.rs build rustlibs
-	$(RUSTC) $(RUSTFLAGS) $(RUSTLIBS) -o $@ src/fileis.rs
+	$(RUSTC) $(RUSTFLAGS) -o $@ src/fileis.rs
 
 .PHONY: fop
 fop: build/bin/fop

README

@@ -18,7 +18,8 @@ anywhere. Other utility sets aim to provide a number of fully-featured
 programs to be used individually, Harakit utilities are meant to be easily
 composable and work together in pipelines.
 
-See docs/ for more on the specific utilities currently implemented.
+See docs/ for more on the specific utilities currently implemented and see
+CONTRIBUTING for guidelines for contributions.
 
 
 Building

STYLE

@@ -1,254 +0,0 @@
-“Everyone knows that debugging is twice as hard as writing a program in the
-first place. So if you’re as clever as you can be when you write it, how
-will you ever debug it?”
-	– Brian Kernighan, The Elements of Programming Style
-
-
-The following guidelines are conducive to clear and readable code that is
-consistent with the style of the rest of the Bonsai Computer System.
-
-
-Use
-===
-
- 0. A single line for control flow statements short enough to be easily
- understood at a glance:
-
-	if !(argc < 0) { usage(program_name); }
-
- This applies to C switch statements and cases and Rust match statements, as
- well:
-
-	switch (value) { /* aligning stuff to make it easier to read is fine */
-		case possibility: variable = foo;  break;
-		default:          variable = NULL; break;
-	}
-
- 1. Switch cases in C and match arms in Rust should start another level of
- indentation:
-
-	switch (value) {
-		case possibility:
-			statement;
-			break;
-		default:
-			statement;
-			break;
-	}
-
-	match result {
-		Ok(n) => variable = n,
-		Err(e) => error = e,
-	}
-
- 2. Braces in control flow where their inclusion is left optional in C:
-
-	if (condition) { statement; }
-
- 3. Empty lines between different kinds of statements:
-
-	int t;
-
-	assert(io->bufuse > 0);
-	assert(io->bufuse <= io->bs);
-
-	if ((t = write(io->fd, io->buf, io->bufuse)) < 0) {
-		io->error = errno;
-		t = 0;
-	} else if (t > 0) {
-		memmove(io->buf, &(io->buf)[t], (io->bufuse -= t));
-	}
-
-	io->bytes += t;
-	io->prec  += (t > 0 && io->bufuse > 0);
-	io->rec   += (t > 0 && io->bufuse == 0);
-
-	return io;
-
- 4. Compiler options that yield the most useful warnings, such as -Wpedantic in
- a lot of C compilers. Fix the warnings, too [0].
-
- 5. One more level of indentation and one argument per line when a function
- call or statement header is too long to fit on one line:
-
-	let usage = format!(
-		"Usage: {} [-d delimiter] index command [args...]",
-		argv[0],
-	);
-
- 6. One more level of indentation than the keyword that initiated a multi-line
- block.
-
-	if (condition) {
-		statement;
-		statement;
-	}
-
- 7. The return value of all non-void functions, or explicitly ignore them (like
- casting to void in C) [0]:
-
-	if ((a = malloc(sizeof char)) == NULL) {          /* handle this error */
-		(void)fprintf(stderr, "oh noes!");   /* explicitly ignore this one */
-		return EX_OSERR;       /* ...because the program is exiting anyway */
-	}
-
- 8. The smallest possible scope for data [0].
-
- 9. Comments noting all the symbols and macros used from a C header file, next
- to its include macro:
-
-	#include <unistd.h> /* close(2), getopt(3), lseek(2), read(2), write(2),
-	(space-aligned)      * optarg, optind, STDIN_FILENO, STDOUT_FILENO */
-
- 10. Spaces in control flow statements, after the keyword and before the
- opening brace:
-
-	for (i = 2; i < argc; ++i) {
-
-
- 11. In Rust, a trailing comma on all arguments or fields that are on their own
- lines:
-
-	return Err(EvaluationError {
-		message: format!("{}: Invalid token", i),
-		code: EX_DATAERR,
-	})
-
- 12. In Rust, place extern statements after use statements that include standard
- library crates. Group like statements:
-
-	use std::fs::Path;
-
-	extern crate strerror;
-	extern crate sysexits;
-
-	use strerror::StrError;
-	use sysexits::{ EX_OSERR, EX_USAGE };
-
- 13. If text is on the same line as a brace, spaces after an opening brace and
- before a closing one:
-
-	use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
-
- 14. Alphabetic sorting, where applicable:
-
-	use std::io::{ BufWriter, Read, Write, stderr, stdin, stdout }
-
- 15. In Rust, use the to_owned() method on string types (str, OsStr, CStr, etc.)
- and the to_string() method on other types.
-
-
-Avoid
-=====
-
- 16. Unbounded loops [0].
-
- 17. Function pointers [0].
-
- 18. Heap memory allocation [0].
-
- 19. Using too much nested logic (within reason).
-
- 20. Too many levels of dereferences [0]:
-
-	/* do not do this */
-	for (size_t i = 0; i < sizeof a / sizeof *a; ++i) {
-		if (a[i].id == MATCH) { a[i].val = 0; }
-	}
-
-	/* do this */
-	for (struct MadeUp *s = &a[0]; *s != NULL; s = &s[1]) {
-		if (s->id == MATCH) { s->val = 0; }
-	}
-
- 21. Using C preprocessor macros; the fewer, the better [0].
-
- 22. The exit(3p) and std::process::exit() functions; returning from the main
- function skips a system call.
-
-
-Do Not Use
-==========
-
- 23. More than the length of one printed page for a function [0].
-
- 24. Recursion, as it’s complex and can unexpectedly overflow the stack [0].
-
- 25. Any functionality not in the POSIX C specification and language features not
- in C99.
-
- 26. Do-while loops, as they’re unique to C and confusing for casual programmers.
-
- 27. Labels and goto statements; use sensible flow control [0].
-
- 28. Pointer arithmetic, as it tends to be confusing and unnecessary; use
- index-reference patterns like &p[1] instead of p + 1. &p[n] is the address at
- p + sizeof p * n, not p + n, like pointer arithmetic suggests.
-
- 29. C struct bitfields in unions, to access certain bits of bigger data types,
- as it’s poorly defined in the C standards; use bit arithmetic.
-
- 30. C trigraphs.
-
- 31. Inclusions in C header files, to prevent multiple file inclusions.
-
- 32. C preprocessor variables to prevent multiple inclusions of the same file,
- such as:
-
-	#ifdef _FILE
-	#define _FILE
-	/* file body */
-	#endif /* ifdef _FILE */
-
- Instead, take the time to ensure other files aren’t including any files twice.
-
- 33. The gets(3p) function from <stdio.h>, as it’s impossible to prevent buffer
- overflows when it's used; use fgets(3p) from <stdio.h>.
-
- 34. The scanf(3p) function from <stdio.h> [1].
-
- 35. Any functionality not described in the latest POSIX make(1) specification.
-
- 36. Macros which panic on failure in Rust (such as the print!() and println!()
- macros). Use a function and handle any errors. However, do use the eprintln!()
- macro for error messages. Handling an error for writing an error message is
- redundant.
-
-
-Usage Text
-==========
-
-This section is adapted from the NetBSD style guide [2].
-
-When programs are invoked incorrectly and in the synopsis of manual pages, uasge
-text should be provided to the user. The following is the format used by this
-project for this purpose:
-
-All optional arguments are to be placed in square brackets (U+005B, U+005D).
-Mutually exclusive arguments can be separated by a vertical line (U+007C).
-Groups of arguments should be specified in alphabetical order in most cases. The
-order of arguments and an example of these rules follows:
-
- 0. Options with no option arguments.
- 1. Options with option arguments. Arguments should be specified inside the same
- square brackets as the options.
- 3. Non-option arguments.
-
-	"usage: f [-aDde] [-b b_arg] [-m m_arg] req1 req2 [opt1 [opt2]]\n"
-	"usage: f [-a | -b] [-c [-de] [-n number]]\n"
-
-
-References
-==========
-
-[0] <https://web.eecs.umich.edu/~imarkov/10rules.pdf>
-[1] <http://sekrit.de/webdocs/c/beginners-guide-away-from-scanf.html>
-[2] <http://cvsweb.netbsd.org/bsdweb.cgi/~checkout~/src/share/misc/style>
-
---
-Copyright © 2024 Emma Tebibyte <emma@tebibyte.media>
-Copyright © 2024 DTB <trinity@trinity.moe>
-Copyright © Wikipedia contributors
-
-This work is licensed under CC BY-SA 4.0. To view a copy of this license, visit
-<http://creativecommons.org/licenses/by-sa/4.0/>.

docs/dj.1

@@ -207,7 +207,7 @@ which are not reported.
 
 This program was based on the
 .BR dd (1p)
-utility as specified in POSIX. While character conversion may have been the
+utility as specified in \*(Px. While character conversion may have been the
 original intent of
 .BR dd (1p),
 it is irrelevant to its modern use. Because of this, this program eschews

docs/false.1

@@ -15,7 +15,7 @@ always be returned.
 .\"
 .SH RATIONALE
 
-In POSIX.1-2017,
+In \*(Px.1-2024,
 .BR false (1p)
 exists for the construction of control flow and loops based on a failure. This
 implementation functions as described in that standard.

docs/fop.1

@@ -11,10 +11,9 @@ fop \(en field operator
 .SH SYNOPSIS
 
 fop
-.RB ( -d )
-.RB [ delimiter ]
-.RB index 
-.RB program...
+.RB [ -d\ delimiter ]
+index program
+.RB [ arguments... ]
 .\"
 .SH DESCRIPTION
 
@@ -26,8 +25,17 @@ Performs operations on specified fields in data read from the standard input.
 Sets a delimiter by which the input data will be split into fields. The default
 is an ASCII record separator.
 .\"
+.SH DIAGNOSTICS
+in the event of an error, a debug message will be printed and the program will
+exit with the appropriate sysexits.h(3) error code.
+.\"
 .SH CAVEATS
 
+If the specified index does not exist in the data, the program
+will print all data to the standard output before exiting with an error. If
+input data is not delimited by the specified delimiter, the program will fill
+memory with the contents of the stream before it is output.
+
 Field indices are zero-indexed, which may be unexpected behavior for some users.
 .\"
 .SH RATIONALE

docs/intcmp.1

@@ -75,7 +75,7 @@ this is elegant but unintuitive.
 .\"
 .SH RATIONALE
 
-The traditional tool for integer comparisons in POSIX and other Unix shells has
+The traditional tool for integer comparisons in \*(Px and other Unix shells has
 been
 .BR test (1).
 This tool also handles string comparisons and file scrutiny. These parts of its

docs/mm.1

@@ -57,7 +57,7 @@ The
 .BR cat (1p)
 and
 .BR tee (1p)
-programs specified in POSIX together provide similar functionality. The
+programs specified in \*(Px together provide similar functionality. The
 separation of the two sets of functionality into separate APIs seemed
 unncessary.
 .\"

docs/npc.1

@@ -45,7 +45,7 @@ The program operates in single-byte chunks regardless of intended encoding.
 .\"
 .SH RATIONALE
 
-POSIX currently lacks a way to display non-printing characters in the terminal
+\*(Px currently lacks a way to display non-printing characters in the terminal
 using a standard tool. A popular extension to
 .BR cat (1p),
 the

docs/rpn.1

@@ -58,7 +58,7 @@ hardware of any given machine.
 
 An infix notation calculation utility,
 .BR bc (1p),
-is included in the POSIX standard, but does not accept expressions as arguments;
+is included in the \*(Px standard, but does not accept expressions as arguments;
 in scripts, any predefined, non-interactive input must be piped into the
 program. A
 .BR dc (1)

docs/strcmp.1

@@ -47,13 +47,13 @@ visual similarity and not byte similarity.
 .\"
 .SH RATIONALE
 
-The traditional tool for string comparisons in POSIX and other Unix shells has
+The traditional tool for string comparisons in \*(Px and other Unix shells has
 been
 .BR test (1).
 This tool also handles integer comparisons and file scrutiny. These parts of its
 functionality have been broken out into multiple utilities.
 
-This program\(cqs functionality may be performed on a POSIX-compliant system
+This program\(cqs functionality may be performed on a \*(Px-compliant system
 with
 .BR test (1p).
 .\"

docs/true.1

@@ -15,7 +15,7 @@ always be returned.
 .\"
 .SH RATIONALE
 
-In \fIPOSIX.1-2017\fP,
+In \fI\*(Px.1-2024\fP,
 .BR true (1p)
 exists for the construction of control flow and loops based on a success. This
 implementation functions as described in that standard.

src/fop.rs

@@ -18,14 +18,16 @@
 
 use std::{
 	env::args,
-	io::{ Error, Read, Write, stdin, stdout },
+	io::{ Error, Write, stdin, stdout },
 	process::{ Command, ExitCode, Stdio, exit },
 };
 
+extern crate delimit;
 extern crate getopt;
 extern crate strerror;
 extern crate sysexits;
 
+use delimit::Delimited;
 use getopt::GetOpt;
 use strerror::StrError;
 use sysexits::{ EX_DATAERR, EX_IOERR, EX_UNAVAILABLE, EX_USAGE };
@@ -90,78 +92,97 @@ fn main() -> ExitCode {
 		exit(usage(&argv[0]).into());
 	});
 
-	/* read entire standard input into memory */
-	let mut buf = String::new();
-	if let Err(e) = stdin().read_to_string(&mut buf) {
-		err(&argv[0], e);
-		exit(EX_IOERR.into());
-	};
+	let stdin = Box::new(stdin().lock());
 
-	/* split the buffer by the delimiter (by default, '\u{1E}') */
-	let mut fields = buf.split(&d).collect::<Vec<&str>>();
+	let mut input = Delimited::new(stdin, d.clone().as_bytes());
+	let mut n = 0;
 
-	/* collect arguments for the operator command */
-	let command_args = argv
-		.iter()
-		.clone()
-		.skip(command_arg + 1) /* skip the command name */
-		.collect::<Vec<&String>>();
+	let mut fopped = false;
 
-	/* spawn the command to operate on the field */
-	let mut spawned = Command::new(operator)
-		.args(command_args) /* spawn with the specified arguments */
-		.stdin(Stdio::piped())
-		.stdout(Stdio::piped()) /* piped stdout to handle output ourselves */
-		.spawn()
-		.unwrap_or_else( |e| {
+	while let Some(i) = input.next() {
+		let v = match i {
+			Ok(v) => v,
+			Err(e) => {
+				err(&argv[0], e);
+				exit(EX_IOERR.into());
+			},
+		};
+
+		let mut out = Vec::new();
+
+		if n == index { /* fop it */
+			/* collect arguments for the operator command */
+			let command_args = argv
+				.iter()
+				.clone()
+				.skip(command_arg + 1) /* skip the command name */
+				.collect::<Vec<&String>>();
+
+			/* spawn the command to operate on the field */
+			let mut spawned = Command::new(operator)
+				.args(command_args) /* spawn with the specified arguments */
+				.stdin(Stdio::piped())
+				/* piped stdout to handle output ourselves */
+				.stdout(Stdio::piped()) 
+				.spawn()
+				.unwrap_or_else( |e| {
+					err(&argv[0], e);
+					exit(EX_UNAVAILABLE.into());
+				});
+
+			/* feed the spawned program’s stdin the field value */
+			if let Some(mut child_stdin) = spawned.stdin.take() {
+				let _ = child_stdin.write_all(&v);
+				drop(child_stdin); /* stay safe! drop your children! */
+
+				let output = spawned.wait_with_output().unwrap_or_else(|e| {
+					err(&argv[0], e);
+					exit(EX_IOERR.into());
+			});
+
+				/* get the output with which the original field will
+				 * be replaced */
+				let mut replace = output.stdout.clone();
+
+				/* pop trailing newline out if the input did not contain it */
+				if v.iter().last() != Some(&b'\n')
+					&& replace.pop() != Some(b'\n')
+				{
+					out = output.stdout;
+				} else {
+					out = replace;
+				}
+			}
+
+			fopped = true;
+		} else {
+			out = v;
+		}
+
+		/* since we cannot know when we’re done, place a new delimiter before
+		 * each index unless it is the 0th */
+		if n != 0 {
+			stdout().write_all(d.as_bytes()).unwrap_or_else(|e| {
+				err(&argv[0], e);
+				exit(EX_IOERR.into());
+			});
+		}
+
+		stdout().write_all(&out).unwrap_or_else(|e| {
 			err(&argv[0], e);
-			exit(EX_UNAVAILABLE.into());
+			exit(EX_IOERR.into());
 		});
 
-	/* get field we want to pipe into spawned program */
-	let field = fields.get(index).unwrap_or_else(|| {
+
+		n += 1;
+	}
+
+	if fopped {
+		return ExitCode::SUCCESS;
+	} else {
 		eprintln!("{}: {}: no such index in input", argv[0], index);
-		exit(EX_DATAERR.into());
-	});
-
-	/* get the stdin of the newly spawned program and feed it the field val */
-	if let Some(mut child_stdin) = spawned.stdin.take() {
-		let _ = child_stdin.write_all(field.as_bytes());
-		drop(child_stdin); /* stay safe! drop your children! */
+		return EX_DATAERR.into();
 	}
 
-	let output = spawned.wait_with_output().unwrap_or_else(|e| {
-		err(&argv[0], e);
-		exit(EX_IOERR.into());
-	});
 
-	/* get the output with which the original field will be replaced */
-	let mut replace = output.stdout.clone();
-
-	/* pop trailing newline out if the input did not contain it */
-	if fields[index].chars().last() != Some('\n') /* no newline */
-		&& replace.pop() != Some(b'\n') { /* pop last char of replacement */
-		/* restore replacement to original command output if popped char was not
-		 * a newline */
-		replace = output.stdout;
-	}
-
-	/* convert the output of the program to UTF-8 */
-	let new_field = String::from_utf8(replace).unwrap_or_else(|e| {
-		eprintln!("{}: {}", argv[0], e);
-		exit(EX_IOERR.into());
-	});
-
-	/* store the new field in the old fields vector */
-	fields[index] = &new_field;
-
-	/* fop it */ 
-	stdout().write_all(
-		fields.join(&d.to_string()).as_bytes()
-	).unwrap_or_else(|e| {
-		err(&argv[0], e);
-		exit(EX_IOERR.into());
-	});
-
-	ExitCode::SUCCESS
 }

src/libdelimit.rs

@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2025 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/.
+ */
+
+use std::{
+    io::{ Read, Result },
+    mem::self,
+};
+
+const BUFFER_SIZE: usize = 4096;
+
+pub struct Delimited {
+    stream: Box<dyn Read>,
+    delimiter: Vec<u8>,
+    buffer: Vec<u8>
+}
+
+impl Delimited {
+	pub fn new(stream: Box<dyn Read>, delimiter: &[u8]) -> Self {
+        Delimited {
+            stream,
+            delimiter: delimiter.to_vec(),
+            buffer: Vec::with_capacity(BUFFER_SIZE),
+        }
+    }
+}
+
+impl Iterator for Delimited {
+    type Item = Result<Vec<u8>>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut buf = [0; BUFFER_SIZE];
+
+        loop {
+            if let Some(p) = find_subslice(&self.buffer, &self.delimiter) {
+                let chunk = self.buffer.drain(..p).collect::<Vec<_>>();
+                
+                let _ = self.buffer.drain(..self.delimiter.len());
+
+                return Some(Ok(chunk));
+            }
+
+            match self.stream.read(&mut buf) {
+                Ok(0) => {
+                    if self.buffer.is_empty() {
+                        return None;
+                    }
+
+                    return Some(Ok(mem::take(&mut self.buffer)));
+                },
+                Ok(n) => {
+                    let content = &buf[..n];
+                    self.buffer.extend_from_slice(&content);
+                },
+                Err(e) => {
+                    return Some(Err(e));
+                },
+            }
+        }
+    }
+}
+
+fn find_subslice(stack: &[u8], key: &[u8]) -> Option<usize> {
+    if key.len() == 1 {
+        return stack.iter().position(|&b| b == key[0]);
+    }
+    if key.len() > stack.len() {
+        return None;
+    }
+    for i in 0..=stack.len() - key.len() {
+        if &stack[i..i + key.len()] == key {
+            return Some(i);
+        }
+    }
+
+    None
+}

src/scrut.c

@@ -1,116 +0,0 @@
-/*
- * Copyright (c) 2023–2024 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 <assert.h> /* assert(3) */
-#include <stdio.h> /* fprintf(3), stderr, NULL */
-#include <stdlib.h> /* EXIT_FAILURE, EXIT_SUCCESS */
-#include <string.h> /* memset(3), strchr(3) */
-#include <sysexits.h> /* EX_OSERR, EX_USAGE */
-#include <unistd.h> /* access(3), getopt(3), pledge(2), unveil(2), F_OK, R_OK,
-					 * W_OK, X_OK */
-#include <sys/stat.h> /* lstat(3), stat struct, S_ISBLK, S_ISCHR, S_ISDIR,
-                       * S_ISFIFO, S_ISGID, S_ISREG, S_ISLNK, S_ISSOCK,
-                       * S_ISUID, S_ISVTX */
-
-char *program_name = "scrut";
-#define OPTS "bcdefgkprsuwxLS"
-/* this is an array so main:sel's size can be known at compile time */
-static char opts[] = OPTS;
-
-static int
-usage(char *argv0) {
-	(void)fprintf(stderr, "Usage: %s [-" OPTS "] file...\n", argv0);
-
-	return EX_USAGE;
-}
-
-int main(int argc, char *argv[]) {
-	char sel[(sizeof opts) / (sizeof *opts)];
-
-	program_name = argv[0] == NULL ? program_name : argv[0];
-
-#ifdef __OpenBSD__
-	if (pledge("rpath stdio unveil", "") == -1) {
-		perror(program_name);
-		return EX_OSERR;
-	}
-#endif
-
-	if (argc < 2) { return usage(program_name); }
-
-	{ /* option parsing */
-		char *p;
-
-		memset(sel, '\0', sizeof sel);
-		for (int c; (c = getopt(argc, argv, opts)) != -1;) {
-			if ((p = strchr(opts, c)) == NULL) { return usage(argv[0]); }
-			else {
-				assert(p - opts < sizeof sel / sizeof *sel); /* bounds check */
-				sel[p - opts] = c;
-			}
-		}
-
-		/* straighten out selections; permute out nulls */
-		p = sel;
-		for (size_t i = 0; i < (sizeof sel) / (sizeof *sel); ++i) {
-			if (sel[i] != '\0') {
-				*p = sel[i];
-				if (&sel[i] != p++) { sel[i] = '\0'; }
-			}
-		}
-	}
-
-	if (optind == argc) { return usage(argv[0]); }
-
-	for (argv += optind ; *argv != NULL; argv = &argv[1]) {
-		struct stat buf;
-
-#ifdef __OpenBSD__
-		if (unveil(*argv, "rw") == -1) {
-			perror(program_name);
-			return EX_OSERR;
-		}
-#endif
-
-		if(access(*argv, F_OK) != 0 || lstat(*argv, &buf) == -1) {
-			return EXIT_FAILURE; /* doesn't exist or isn't stattable */
-		}
-
-		for (size_t i = 0; sel[i] != '\0'; ++i) {
-			if (
-					(sel[i] == 'b' && !S_ISBLK(buf.st_mode))
-					|| (sel[i] == 'c' && !S_ISCHR(buf.st_mode))
-					|| (sel[i] == 'd' && !S_ISDIR(buf.st_mode))
-					|| (sel[i] == 'e' && 0)
-					|| (sel[i] == 'f' && !S_ISREG(buf.st_mode))
-					|| (sel[i] == 'g' && !(buf.st_mode & S_ISGID))
-					|| (sel[i] == 'k' && !(buf.st_mode & S_ISVTX))
-					|| (sel[i] == 'p' && !S_ISFIFO(buf.st_mode))
-					|| (sel[i] == 'r' && access(*argv, R_OK) != 0)
-					|| (sel[i] == 'u' && !(buf.st_mode & S_ISUID))
-					|| (sel[i] == 'w' && access(*argv, W_OK) != 0)
-					|| (sel[i] == 'x' && access(*argv, X_OK) != 0)
-					|| (sel[i] == 'L' && !S_ISLNK(buf.st_mode))
-					|| (sel[i] == 'S' && !S_ISSOCK(buf.st_mode))
-			) { return EXIT_FAILURE; }
-		}
-	}
-
-	return EXIT_SUCCESS;
-}