init

.clang-format

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+# CS 631 - Advanced Programming in the Unix Environment
+# clang-format source code format file
+# Author: Anthony Webster
+#
+# I created this file based on the criteria specified at <https://stevens.netmeister.org/631/style>.
+# I don't really care what you do with this file. I've just written this to (hopefully) be helpful.
+# But, because it's "the right thing to do", this file is licensed under the MIT license.
+#
+# Copyright (c) 2024 Anthony Webster
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+BasedOnStyle: LLVM
+# Despite my strong disagreement with using 80 columns, the style guide says we
+# should try to keep code within 80 columns. So I guess we have to set this to 80.
+ColumnLimit: 80
+TabWidth: 4
+IndentWidth: 4
+UseTab: AlignWithSpaces
+LineEnding: LF
+InsertBraces: true
+IndentCaseBlocks: false
+BreakBeforeBraces: Linux
+MaxEmptyLinesToKeep: 2
+IncludeBlocks: Regroup
+SortIncludes: CaseInsensitive
+IncludeCategories:
+  # Kernel includes first
+  - Regex: '^<sys/'
+    Priority: 1
+    SortPriority: 1
+    CaseSensitive: false
+  # Network includes after kernel includes, without a blank line
+  - Regex: '^<(net|netinet|protocols)/'
+    Priority: 1
+    SortPriority: 2
+    CaseSensitive: false
+  # /usr includes next, separated by a blank line
+  - Regex: '^<'
+    Priority: 2
+    SortPriority: 3
+    CaseSensitive: false
+  # And other includes after /usr, separated by a blank line
+  - Regex: '^"'
+    Priority: 3
+    SortPriority: 4
+    CaseSensitive: false
+
+# These aren't explicitly stated in the style guide but are derived from how the style guide is formatted.
+BitFieldColonSpacing: None
+SpaceAfterLogicalNot: false
+SpaceBeforeAssignmentOperators: true
+QualifierAlignment: Left
+PointerAlignment: Right
+AllowShortFunctionsOnASingleLine: None
+AlwaysBreakAfterDefinitionReturnType: All
+SeparateDefinitionBlocks: Always
+SpaceAfterCStyleCast: false
+AllowShortIfStatementsOnASingleLine: false
+AllowShortBlocksOnASingleLine: Never
+AllowShortLoopsOnASingleLine: false
+AllowShortEnumsOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+ContinuationIndentWidth: 4
+
+

.gitignore

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+*.o
+ls

Makefile

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+CC = gcc
+CFLAGS = -g -Wall -Werror -Wextra -Wformat=2 -Wjump-misses-init -Wlogical-op -Wpedantic -Wshadow
+#CFLAGS = -ansi -g -Wall -Werror -Wextra -Wformat=2 -Wjump-misses-init -Wlogical-op -Wpedantic -Wshadow
+#CFLAGS = -Wall -Werror -Wextra -Wpedantic 
+EXECUTABLE = ls
+
+SOURCES = ls.c
+OBJECTS = $(SOURCES:.c=.o)
+
+all: $(EXECUTABLE)
+
+$(EXECUTABLE): $(OBJECTS)
+	$(CC) $(OBJECTS) -o $(EXECUTABLE) $(LDFLAGS)
+
+%.o: %.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+clean:
+	rm -f $(OBJECTS) $(EXECUTABLE)
+
+.PHONY: all clean

checklist

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+For each assignment, copy this file into your homework
+submission directory and answer all questions.
+
+Did I write all the code myself?
+   - Don't copy and paste code from the internet, your
+     classmates, sample solutions, or anywhere else.
+     Review https://stevens.netmeister.org/631/#plagiarism
+
+
+Did I use any AI technologies?  If so, did I properly
+acknowledge this help?
+   - Review https://stevens.netmeister.org/631/use-of-ai.html
+
+
+Does my code follow the style guide?
+   - Code is communication.  Make sure your code is
+     readable, well-structured, properly indented,
+     with sensibily named variables and functions.
+
+yes i use a clang formatter a classmate wrote
+
+
+Does my code compile without warnings or errors on a
+NetBSD 10.0 system?
+  - Always use *at least* 'cc -Wall -Werror -Wextra',
+    possibly
+    'cc -ansi -g -Wall -Werror -Wextra -Wformat=2 -Wjump-misses-init -Wlogical-op -Wpedantic -Wshadow'.
+
+yes
+
+Did I provide a Makefile?
+  - 'make' should use the above CFLAGS and produce an
+    executable
+
+yup
+
+Did I provide a README to explain any problems or
+issues I encountered?
+  - Make sure that your text is well-formatted, plain
+    ASCII in proper English.  Use a spell checker.
+
+yes
+
+Did I check the return value of all function calls?
+  - Yes, that does include but is not limited to malloc(3).
+
+for non atomic / fillable ones yes
+
+Did I send error messages to stderr?  Did I use
+strerror(3) or perror(3) etc. to print meaningful
+error messages?
+
+yeah we have a unified err interface!! 
+
+Did I use only meaningful and necessary comments?
+  - Your comments should explain the 'why', not the
+    'what'.
+
+yes
+
+Does my program only generate meaningful output?
+Debugging information should be removed.
+
+yes
+
+Does my program return zero on success, non-zero otherwise?
+
+yeah
+
+
+Did I make sure that my .h files only include function
+forward declarations, macros, etc., no function
+implementations or other code?
+
+n/a
+
+Did I check that I have avoided code duplication?
+Writing the same or very similar code multiple times
+is a sign that my program could benefit from being
+restructured.
+
+yes
+
+For any string manipulation, did I use size-bounded
+functions?
+  - Use strlcat(3)/strlcpy(3) instead of
+    strcat(3)/strcpy(3) etc.
+yeah

ls.c

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+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <dirent.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libgen.h>
+#include <limits.h>
+#include <stdarg.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+void ls_ent(const char *path);
+void do_regfile(const char *path, const struct stat *sb);
+void do_dir(const char *path, const struct stat *sb);
+void do_symlink(const char *path, const struct stat *sb);
+void do_blockdev(const char *path, const struct stat *sb);
+void do_char(const char *path, const struct stat *sb);
+void do_fifo(const char *path, const struct stat *sb);
+void do_socket(const char *path, const struct stat *sb);
+void do_unknown(const char *path, const struct stat *sb);
+
+int
+main(int argc, char *argv[])
+{
+	int i;
+	if (argc == 1) {
+		ls_ent(".");
+	} else {
+		for (i = 1; i < argc; i++) {
+			if (argv[i][0] == '-') {
+				/* argparsing */
+			} else {
+				ls_ent(argv[i]);
+			}
+		}
+	}
+	return 0;
+}
+
+void
+ls_ent(const char *path)
+{
+	struct stat sb;
+	if (lstat(path, &sb) == -1) {
+		err(1, "Failed to stat %s", path);
+	}
+	switch (sb.st_mode & S_IFMT) {
+	case S_IFREG:
+		do_regfile(path, &sb);
+		break;
+	case S_IFDIR:
+		do_dir(path, &sb);
+		break;
+	case S_IFLNK:
+		do_symlink(path, &sb);
+		break;
+	case S_IFCHR:
+		do_char(path, &sb);
+		break;
+	case S_IFIFO:
+		do_fifo(path, &sb);
+		break;
+	case S_IFSOCK:
+		do_socket(path, &sb);
+		break;
+	default:
+		do_unknown(path, &sb);
+		break;
+	}
+}
+
+void
+do_regfile(const char *path, const struct stat *sb)
+{
+	(void)sb;
+	printf("reg: %s\n", path);
+}
+
+void
+do_dir(const char *path, const struct stat *sb)
+{
+	DIR *d;
+	struct dirent *dir;
+	char full_path[PATH_MAX];
+
+	(void)sb;
+	d = opendir(path);
+	if (!d) {
+		err(1, "Failed to open dir: %s", path);
+	}
+	printf("dir: %s\n", path);
+	while ((dir = readdir(d))) {
+		/* avoids infinite recursion :( */
+		if (strcmp(dir->d_name, ".") == 0 || strcmp(dir->d_name, "..") == 0) {
+			continue;
+		}
+		snprintf(full_path, sizeof(full_path), "%s/%s", path, dir->d_name);
+		ls_ent(full_path);
+	}
+	closedir(d);
+}
+
+void
+do_symlink(const char *path, const struct stat *sb)
+{
+	(void)sb;
+	printf("sym: %s\n", path);
+}
+
+void
+do_blockdev(const char *path, const struct stat *sb)
+{
+	(void)sb;
+	printf("blk: %s\n", path);
+}
+
+void
+do_char(const char *path, const struct stat *sb)
+{
+	(void)sb;
+	printf("char: %s\n", path);
+}
+
+void
+do_fifo(const char *path, const struct stat *sb)
+{
+	(void)sb;
+	printf("fifo: %s\n", path);
+}
+
+void
+do_socket(const char *path, const struct stat *sb)
+{
+	(void)sb;
+	printf("sock: %s\n", path);
+}
+
+void
+do_unknown(const char *path, const struct stat *sb)
+{
+	(void)sb;
+	printf("wtf: %s\n", path);
+}

lstest.sh

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+#! /bin/sh
+#set -e
+
+COMMANDS="./ls
+./ls -l
+./ls -la
+./ls -lai
+./ls -lairt
+./ls -lairtus
+./ls -d
+./ls -d .
+./ls -d . .. /
+./ls -n /home
+./ls -l /dev
+./ls -lsh
+./ls -lF
+./ls -A ~/testdir
+./ls -w ~/testdir
+./ls ~/testdir | more
+./ls ~/testdir/d
+./ls -l ~/testdir/d
+./ls -la ~/testdir/d
+BLOCKSIZE=bacon ./ls -ls
+BLOCKSIZE=0 ./ls -ls
+BLOCKSIZE=2048 ./ls -ls
+BLOCKSIZE=-50 ./ls -ls
+BLOCKSIZE=50 ./ls -ls
+TZ=PST8PDT ./ls -lc
+TZ=bacon ./ls -lc
+./ls -lks
+./ls / /tmp ~ .
+./ls -?
+./ls /does/not/exit
+./ls /nowhere"
+
+IFS="
+"
+
+for c in ${COMMANDS}; do
+	echo ${c}
+	timeout --foreground 60 sh -c "eval ${c}" || echo timed out
+done
+
+echo "./ls -lR /"
+timeout 600 ./ls -lR / || echo timed out

mktestdir.sh

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+#! /bin/sh
+
+set -e
+
+mkdir -p testdir
+cd testdir
+
+mkdir d
+touch empty
+mkfifo fifo
+echo file > file
+ln file file2
+ln -s "" emptylink
+ln -s /nowhere
+ln -s file2 symlink
+touch -a -t 201810012222 atime
+touch -t 196912010000 longago
+touch -t 300011111111 inthefuture
+mkdir subdir
+chmod 1755 subdir
+ln -s . subdir/loopdir
+touch executable
+chmod 755 executable
+touch suid:sgid
+chmod 6755 suid:sgid
+touch missing-exec
+chmod 4000 missing-exec
+touch " "
+touch "	"
+touch "foo
bar"
+
+su root -c "chown nobody:operator file"
+su root -c "chown games:daemon d"
+#sudo chown nobody:operator file
+#sudo chown games:daemon d
+#su root -c "cp /dev/wd0 ."
+touch noowner
+su root -c "chown 1234 noowner"
+#sudo chown 1234 noowner
+touch nogroup
+su root -c "chown :1234 nogroup"
+#sudo chown :1234 nogroup
+ln -s / "ls-LR"
+su root -c "cp -a /dev/null null"
+#sudo cp -a /dev/null null
+touch $(yes a | head -255 | tr -d '\n')
+
+cat >hole.c <<EOF
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+char buf1[] = "abcdefghij";
+char buf2[] = "ABCDEFGHIJ";
+
+#define BIGNUM 10240000
+
+int
+main(void) {
+	int fd;
+
+	if ((fd = creat("file.hole", S_IRUSR | S_IWUSR)) < 0) {
+		perror("creat error");
+		return EXIT_FAILURE;
+	}
+	if (write(fd, buf1, strlen(buf1)) != (ssize_t)strlen(buf1)) {
+		perror("error writing buf1");
+		return EXIT_FAILURE;
+	}
+
+	if (lseek(fd, BIGNUM, SEEK_CUR) == -1) {
+		perror("lseek error");
+		return EXIT_FAILURE;
+	}
+
+	if (write(fd, buf2, strlen(buf2)) != (ssize_t)strlen(buf2)) {
+		perror("error writing buf2");
+		return EXIT_FAILURE;
+	}
+
+	return EXIT_SUCCESS;
+}
+EOF
+
+cc -Wall -Werror hole.c
+./a.out
+
+mkdir nested
+cd nested
+(
+for i in `jot 512`; do
+	mkdir $i
+	cd $i
+done
+)
+
+(
+for i in `jot 30`; do
+	mkdir `yes a | head -255 | tr -d '\n'`
+	ln -s a* b
+	cd b
+done
+)

readme.rst

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+==
+ls
+==
+
+
+above was spellchecked by claude3

shell.nix

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+{ pkgs ? import <nixpkgs> {}}:
+
+pkgs.mkShell {
+  buildInputs = with pkgs; [
+    gcc
+    clang-tools
+  ];
+}