Added a simple shell, jsh

25 files changed, 336 insertions, 321 deletions

diff --git a/.DS_Store b/.DS_Store
deleted file mode 100644
index b48a754..0000000
--- a/.DS_Store
+++ /dev/null
diff --git a/.vscode/configurationCache.log b/.vscode/configurationCache.log
deleted file mode 100644
index 3fb4b13..0000000
--- a/.vscode/configurationCache.log
+++ /dev/null
@@ -1 +0,0 @@
-{"buildTargets":["all","clean","install","src"],"launchTargets":[],"customConfigurationProvider":{"workspaceBrowse":{"browsePath":[],"compilerArgs":[]},"fileIndex":[]}}
\ No newline at end of file
diff --git a/.vscode/dryrun.log b/.vscode/dryrun.log
deleted file mode 100644
index 51f061e..0000000
--- a/.vscode/dryrun.log
+++ /dev/null
@@ -1,5 +0,0 @@
-make all -f "/Users/jmm/Documents/git/ProjectMustang/makefile" --dry-run --always-make --keep-going --print-directory

-make: Entering directory `/Users/jmm/Documents/git/ProjectMustang'
-make: Nothing to be done for `all'.
-make: Leaving directory `/Users/jmm/Documents/git/ProjectMustang'
- 

diff --git a/.vscode/settings.json b/.vscode/settings.json
deleted file mode 100644
index 65e1ec0..0000000
--- a/.vscode/settings.json
+++ /dev/null
@@ -1,3 +0,0 @@
-{
-    "makefile.extensionOutputFolder": "./.vscode"
-}
\ No newline at end of file
diff --git a/.vscode/targets.log b/.vscode/targets.log
deleted file mode 100644
index 4086f67..0000000
--- a/.vscode/targets.log
+++ /dev/null
@@ -1,275 +0,0 @@
-make all -f "/Users/jmm/Documents/git/ProjectMustang/makefile" --print-data-base --no-builtin-variables --no-builtin-rules --question

-# GNU Make 3.81
-# Copyright (C) 2006  Free Software Foundation, Inc.
-# This is free software; see the source for copying conditions.
-# There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
-# PARTICULAR PURPOSE.
-
-# This program built for i386-apple-darwin11.3.0
-
-# Make data base, printed on Mon Nov  1 11:39:40 2021
-
-# Variables
-
-# automatic
-<D = $(patsubst %/,%,$(dir $<))
-# automatic
-?F = $(notdir $?)
-# environment
-VSCODE_LOG_NATIVE = false
-# automatic
-?D = $(patsubst %/,%,$(dir $?))
-# automatic
-@D = $(patsubst %/,%,$(dir $@))
-# automatic
-@F = $(notdir $@)
-# makefile
-CURDIR := /Users/jmm/Documents/git/ProjectMustang
-# makefile
-SHELL = /bin/sh
-# environment
-VSCODE_NLS_CONFIG = {"locale":"en-us","availableLanguages":{},"_languagePackSupport":true}
-# environment
-_ = /usr/bin/make
-# makefile (from `/Users/jmm/Documents/git/ProjectMustang/makefile', line 1)
-MAKEFILE_LIST :=  /Users/jmm/Documents/git/ProjectMustang/makefile
-# environment
-VSCODE_VERBOSE_LOGGING = true
-# environment
-__CFBundleIdentifier = com.visualstudio.code.oss
-# environment
-INFOPATH = /opt/homebrew/share/info:
-# environment
-PLAN9 = /opt/plan9port
-# environment
-VSCODE_IPC_HOOK_EXTHOST = /var/folders/qq/frtrjqf10vlcgdw8_fwlhm_c0000gn/T/vscode-ipc-0d1cd7ca-fb65-4182-a0f6-057ab4f3f736.sock
-# environment
-VSCODE_CWD = /
-# environment
-PATH = /opt/ProjectMustang/bin:/Users/jmm/.local/bin:/opt/CEdev/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/go/bin:/opt/X11/bin:/Library/Apple/usr/bin:/Library/Frameworks/Mono.framework/Versions/Current/Commands:/opt/plan9port/bin
-# environment
-ZDOTDIR = /Users/jmm/.config/shells/zsh
-# environment
-VSCODE_LOG_STACK = false
-# environment
-ELECTRON_RUN_AS_NODE = 1
-# default
-.FEATURES := target-specific order-only second-expansion else-if archives jobserver check-symlink
-# environment
-SSH_AUTH_SOCK = /private/tmp/com.apple.launchd.rBEHA7GWj3/Listeners
-# automatic
-%F = $(notdir $%)
-# makefile (from `/Users/jmm/Documents/git/ProjectMustang/makefile', line 1)
-(CC) = clang
-# environment
-DISPLAY = /private/tmp/com.apple.launchd.gZJXoHdnVC/org.xquartz:0
-# automatic
-*F = $(notdir $*)
-# environment
-VSCODE_PIPE_LOGGING = true
-# environment
-PWD = /Users/jmm/Documents/git/ProjectMustang
-# environment
-HOMEBREW_CELLAR = /opt/homebrew/Cellar
-# environment
-ORIGINAL_XDG_CURRENT_DESKTOP = undefined
-# environment
-MANPATH = /opt/homebrew/share/man::
-# environment
-VSCODE_AMD_ENTRYPOINT = vs/workbench/services/extensions/node/extensionHostProcess
-# environment
-HOME = /Users/jmm
-# environment
-XDG_CACHE_HOME = /Users/jmm/.cache
-# default
-MAKEFILEPATH := /Applications/Xcode.app/Contents/Developer/Makefiles
-# environment
-VSCODE_CODE_CACHE_PATH = /Users/jmm/Library/Application Support/VSCodium/CachedData/6cba118ac49a1b88332f312a8f67186f7f3c1643
-# environment
-LOGNAME = jmm
-# environment
-APPLICATION_INSIGHTS_NO_DIAGNOSTIC_CHANNEL = true
-# environment
-ZSH = /Users/jmm/.config/shells/zsh
-# environment
-VSCODE_HANDLES_UNCAUGHT_ERRORS = true
-# automatic
-^D = $(patsubst %/,%,$(dir $^))
-# environment
-ProMust = /opt/ProjectMustang
-# environment
-SHELLDIR = /Users/jmm/.config/shells
-# environment
-XPC_FLAGS = 0x0
-# default
-MAKE = $(MAKE_COMMAND)
-# default
-MAKECMDGOALS := all
-# environment
-SHLVL = 1
-# default
-MAKE_VERSION := 3.81
-# environment
-USER = jmm
-# makefile
-.DEFAULT_GOAL := src
-# automatic
-%D = $(patsubst %/,%,$(dir $%))
-# default
-MAKE_COMMAND := /Applications/Xcode.app/Contents/Developer/usr/bin/make
-# default
-.VARIABLES := 
-# environment
-TMPDIR = /var/folders/qq/frtrjqf10vlcgdw8_fwlhm_c0000gn/T/
-# environment
-CEDEV = /opt/CEdev
-# environment
-VSCODE_IPC_HOOK = /Users/jmm/Library/Application Support/VSCodium/1.61.2-main.sock
-# makefile
-MAKEFLAGS = Rrqp
-# environment
-MFLAGS = -Rrqp
-# automatic
-*D = $(patsubst %/,%,$(dir $*))
-# environment
-HOMEBREW_SHELLENV_PREFIX = /opt/homebrew
-# environment
-XPC_SERVICE_NAME = application.com.visualstudio.code.oss.20131101.20131106
-# environment
-HOMEBREW_PREFIX = /opt/homebrew
-# automatic
-+D = $(patsubst %/,%,$(dir $+))
-# automatic
-+F = $(notdir $+)
-# environment
-HOMEBREW_REPOSITORY = /opt/homebrew
-# environment
-__CF_USER_TEXT_ENCODING = 0x1F5:0x0:0x0
-# environment
-COMMAND_MODE = unix2003
-# default
-MAKEFILES := 
-# automatic
-<F = $(notdir $<)
-# environment
-XDG_CONFIG_HOME = /Users/jmm/.config
-# environment
-LC_ALL = C
-# environment
-LESSHISTFILE = -
-# automatic
-^F = $(notdir $^)
-# environment
-XDG_DATA_HOME = /Users/jmm/.local/share
-# default
-SUFFIXES := 
-# default
-.INCLUDE_DIRS = /usr/local/include
-# makefile (from `/Users/jmm/Documents/git/ProjectMustang/makefile', line 4)
-PROROOT := /Users/jmm/Documents/git/ProjectMustang
-# environment
-MAKELEVEL := 0
-# environment
-ENV = /Users/jmm/.config/shells/ksh/kshrc
-# makefile (from `/Users/jmm/Documents/git/ProjectMustang/makefile', line 3)
-SUBDIRS := src
-# environment
-LANG = C
-# environment
-VSCODE_PID = 30994
-# variable set hash-table stats:
-# Load=83/1024=8%, Rehash=0, Collisions=3/113=3%
-
-# Pattern-specific Variable Values
-
-# No pattern-specific variable values.
-
-# Directories
-
-
-# No files, no impossibilities in 0 directories.
-
-# Implicit Rules
-
-# No implicit rules.
-
-# Files
-
-all:
-#  Phony target (prerequisite of .PHONY).
-#  Command-line target.
-#  Implicit rule search has not been done.
-#  File does not exist.
-#  File has been updated.
-#  Successfully updated.
-
-.PHONY: install all clean src
-#  Implicit rule search has not been done.
-#  Modification time never checked.
-#  File has not been updated.
-
-# Not a target:
-/Users/jmm/Documents/git/ProjectMustang/makefile:
-#  Implicit rule search has been done.
-#  Last modified 2021-10-10 19:11:05
-#  File has been updated.
-#  Successfully updated.
-# variable set hash-table stats:
-# Load=0/32=0%, Rehash=0, Collisions=0/0=0%
-
-# Not a target:
-.SUFFIXES:
-#  Implicit rule search has not been done.
-#  Modification time never checked.
-#  File has not been updated.
-
-src:
-#  Phony target (prerequisite of .PHONY).
-#  Implicit rule search has not been done.
-#  File does not exist.
-#  File has not been updated.
-#  commands to execute (from `/Users/jmm/Documents/git/ProjectMustang/makefile', line 9):
-	$(MAKE) -C $@ $(MAKECMDGOALS)
-	
-
-# Not a target:
-.DEFAULT:
-#  Implicit rule search has not been done.
-#  Modification time never checked.
-#  File has not been updated.
-
-clean: src
-#  Phony target (prerequisite of .PHONY).
-#  Implicit rule search has not been done.
-#  File does not exist.
-#  File has not been updated.
-#  commands to execute (from `/Users/jmm/Documents/git/ProjectMustang/makefile', line 18):
-	@rm $(wildcard build/bin/*)
-	
-
-install:
-#  Phony target (prerequisite of .PHONY).
-#  Implicit rule search has not been done.
-#  File does not exist.
-#  File has not been updated.
-#  commands to execute (from `/Users/jmm/Documents/git/ProjectMustang/makefile', line 14):
-	@rm -r /opt/ProjectMustang
-	@cp -r build/ /opt/ProjectMustang/
-	
-
-# files hash-table stats:
-# Load=8/1024=1%, Rehash=0, Collisions=0/26=0%
-# VPATH Search Paths
-
-# No `vpath' search paths.
-
-# No general (`VPATH' variable) search path.
-
-# # of strings in strcache: 1
-# # of strcache buffers: 1
-# strcache size: total = 4096 / max = 4096 / min = 4096 / avg = 4096
-# strcache free: total = 4047 / max = 4047 / min = 4047 / avg = 4047
-
-# Finished Make data base on Mon Nov  1 11:39:40 2021
-
- 

diff --git a/makefile b/makefile
index b35e42a..0185b2e 100644..100755
--- a/makefile
+++ b/makefile
@@ -1,4 +1,4 @@
-export (CC) = clang
+export (CC) = gcc
 #TOPTARGETS := all
 SUBDIRS := src
 export PROROOT := ${CURDIR}
@@ -8,7 +8,9 @@ export PROROOT := ${CURDIR}
 $(SUBDIRS):
 	$(MAKE) -C $@ $(MAKECMDGOALS)
 
-all: $(SUBRIRS)
+all: build install
+
+build: $(SUBDIRS)
 
 install:
 	@rm -r /opt/ProjectMustang
@@ -17,4 +19,4 @@ install:
 clean: $(SUBDIRS)
 	@rm $(wildcard build/bin/*)
 
-.PHONY: install all clean $(TOPTARGETS) $(SUBDIRS)
+.PHONY: install build all clean $(TOPTARGETS) $(SUBDIRS)
diff --git a/src/.DS_Store b/src/.DS_Store
index 29f25d4..e76ba5a 100644
--- a/src/.DS_Store
+++ b/src/.DS_Store
diff --git a/src/cmd/.DS_Store b/src/cmd/.DS_Store
index ddbc73c..5047d2a 100644
--- a/src/cmd/.DS_Store
+++ b/src/cmd/.DS_Store
diff --git a/src/cmd/cat/cat.c b/src/cmd/cat/cat.c
new file mode 100755
index 0000000..1c3e40a
--- /dev/null
+++ b/src/cmd/cat/cat.c
@@ -0,0 +1,54 @@
+#include <stdio.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <stdbool.h>
+
+void fileoutput(FILE *, const char *);
+bool isdir(const char *);
+
+/* concatinate files to a file stream */
+int main(int argc, char **argv)
+{
+	FILE *fp;
+	if (argc == 1) {
+		fileoutput(stdin, "stdin");
+	} else {
+		while (--argc > 0 && !ferror(stdout)) {
+			if (isdir(*++argv)) {
+				perror("cat");
+				continue;
+			}
+			if ((fp = fopen(*argv, "r")) == NULL) {
+				perror("cat");
+				continue;
+			}
+			fileoutput(fp, *argv);
+		}
+	}
+	if (ferror(stdout)) {
+		perror("cat");
+		return -1;
+	}
+	return 0;
+}
+
+/* fileoutput: output a file to stdout */
+void fileoutput(FILE *fp, const char *name)
+{
+	int c;
+	while ((c = getc(fp)) != EOF)
+		putc(c, stdout);
+	if (ferror(fp)) {
+		perror("cat");
+	}
+	fclose(fp);
+}
+
+/* isdir: return true if the file as the path is a directory */
+bool isdir(const char *path)
+{
+	struct stat sbuf;
+	stat(path, &sbuf);
+	return S_ISDIR(sbuf.st_mode);
+}
+
diff --git a/src/cmd/cat/makefile b/src/cmd/cat/makefile
new file mode 100755
index 0000000..bb8db9e
--- /dev/null
+++ b/src/cmd/cat/makefile
@@ -0,0 +1,12 @@
+CFLAGS=-Wall -Werror
+
+build: cat
+	@cp cat $(PROROOT)/build/bin/cat
+
+cat: cat.c
+	$(CC) $(CFLAGS) -o cat cat.c
+
+clean:
+	@rm -r cat
+
+.PHONY: build clean
diff --git a/src/cmd/coin/coin.c b/src/cmd/coin/coin.c
index c18d66c..4471959 100644
--- a/src/cmd/coin/coin.c
+++ b/src/cmd/coin/coin.c
@@ -4,61 +4,58 @@
 #include <string.h>
 #include <limits.h>
 
-unsigned long coinFlip (unsigned long times);
+int coinFlip (int times);
 
 int
 main (int argc, char *argv[])
 {
-	int nflag = 0, i, mflag = 0;
-	unsigned long times = 1, tails, heads;
+	int nflag = 0, times = 1, i, tails, heads;
+	float ph, pt;
 	argc--;
 
 	for (i = 1; i <= argc; i++) {
-		if (strcmp(argv[i], "-n") == 0)
+		if (strcmp(argv[i], "-n") == 0) {
 			nflag++;
-		else if (strcmp(argv[i], "-m") == 0) {
-			mflag++;
+		} else if (strcmp(argv[i], "-m") == 0) {
+			times = INT_MAX;
 			break;
-		} else if (nflag == 1)
+		} else if (nflag == 1) {
 			times = atoi(argv[i]);
 			if (times == 0) {
 				printf("Non Integer Value Inputted\n");
 				return -1;
 			}
+			break;
+		}
 	}
 
-	if (mflag == 1)
-		times = ULONG_MAX;
-
 	if (times == 1)
 		printf("%s\n", coinFlip(times) ? "Heads" : "Tails");
 	else {
 		tails = coinFlip(times);
 		heads = times - tails;
-		float ph = (float)heads/times, pt = (float)tails/times;
+		ph = (float)heads/times;
+		pt = (float)tails/times;
 
-		printf("Heads: %lu\nTails: %ld\nProb Heads: %f\nProb Tails: %f\n", heads, tails, ph, pt);
+		printf("Heads: %d\nTails: %d\nProb Heads: %f\nProb Tails: %f\n", heads, tails, ph, pt);
 	}
 
 	return 0;
 }
 
 /* coinFlip: Flips a coin n numbers of times and returns the number of tails */
-unsigned long 
-coinFlip (unsigned long times)
+int 
+coinFlip (int times)
 {
-	unsigned long tails, i;
-	int c;
+	int tails, i, c;
 	time_t t;
 	srand((unsigned) time(&t));
 
-	tails = 0;
-
-	for (i = 0; i < times; i++) {
+	for (i = tails = 0; i < times; i++) {
 		c = rand() % 2;
 		if (c == 1)
 			tails++;
 	}
 
 	return tails;
-}
\ No newline at end of file
+}
diff --git a/src/cmd/coin/makefile b/src/cmd/coin/makefile
index cf8289d..7cd5d6e 100644..100755
--- a/src/cmd/coin/makefile
+++ b/src/cmd/coin/makefile
@@ -1,10 +1,12 @@
-all: coin
+CFLAGS=-Wall -Werror
+
+build: coin
 	@cp coin $(PROROOT)/build/bin/coin
 
 coin: coin.c
-	$(CC) -o coin coin.c
+	$(CC) $(CFLAGS) -o coin coin.c
 
 clean:
 	@rm -r coin
 
-.PHONY: all clean
\ No newline at end of file
+.PHONY: build clean
diff --git a/src/cmd/dice/dice.c b/src/cmd/dice/dice.c
index f211d67..b31670f 100644
--- a/src/cmd/dice/dice.c
+++ b/src/cmd/dice/dice.c
@@ -12,4 +12,4 @@ main (void)
 	printf("%d\n", (rand() % sides) + 1);
 
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/src/cmd/dice/makefile b/src/cmd/dice/makefile
index 5c0e384..2acc850 100644..100755
--- a/src/cmd/dice/makefile
+++ b/src/cmd/dice/makefile
@@ -1,10 +1,12 @@
-all: dice
+CFLAGS=-Wall -Werror
+
+build: dice
 	@cp dice $(PROROOT)/build/bin/dice
 
 dice: dice.c
-	$(CC) -o dice dice.c
+	$(CC) $(CFLAGS) -o dice dice.c
 
 clean:
 	@rm -r dice
 
-.PHONY: all clean
\ No newline at end of file
+.PHONY: build clean
diff --git a/src/cmd/echo/echo.c b/src/cmd/echo/echo.c
index 3dc8334..4733830 100644
--- a/src/cmd/echo/echo.c
+++ b/src/cmd/echo/echo.c
@@ -14,4 +14,4 @@ main (int argc, char *argv[])
 			printf("%s%c", argv[i], (i == argc) ? ((nflag == 1) ? '\0' : '\n') : ' ');
 	}
 	return 0;
-}
\ No newline at end of file
+}
diff --git a/src/cmd/echo/makefile b/src/cmd/echo/makefile
index 0301f23..59f976f 100644..100755
--- a/src/cmd/echo/makefile
+++ b/src/cmd/echo/makefile
@@ -1,10 +1,12 @@
-all: echo
+CFLAGS=-Wall -Werror
+
+build: echo
 	@cp echo $(PROROOT)/build/bin/echo
 
 echo: echo.c
-	$(CC) -o echo echo.c
+	$(CC) $(CFLAGS) -o echo echo.c
 
 clean:
 	@rm -r echo
-	
-.PHONY: all clean
\ No newline at end of file
+
+.PHONY: build clean
diff --git a/src/cmd/jsh/README.md b/src/cmd/jsh/README.md
new file mode 100755
index 0000000..db638ed
--- /dev/null
+++ b/src/cmd/jsh/README.md
@@ -0,0 +1,3 @@
+#J-Shell (jsh)
+
+J-Shell is a simple unix shell written in C.
diff --git a/src/cmd/jsh/jsh.c b/src/cmd/jsh/jsh.c
new file mode 100755
index 0000000..320a93d
--- /dev/null
+++ b/src/cmd/jsh/jsh.c
@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <ctype.h>
+
+size_t getargs(const size_t n, char *args[n], FILE * const stream);
+int shellexec(size_t n, char * const args[n]);
+
+static bool run = true;
+
+int main(int argc, char *argv[]) {
+	char *words[BUFSIZ] = {NULL};
+	FILE *fp = stdin;
+	size_t numberofwords = 0;
+	if (argc == 2) {
+		if ((fp = fopen(argv[1], "r")) == NULL) {
+			perror("jsh");
+			return EXIT_FAILURE;
+		}
+	}
+	while (run) {
+		printf("$ ");
+		numberofwords = getargs(BUFSIZ, words, fp);
+		shellexec(BUFSIZ, words);
+		for (int i = 0; i < numberofwords; i++) {
+			free(words[i]);
+			words[i] = NULL;
+		}
+	}
+	return 0;
+}
+
+size_t getargs(const size_t n, char *args[n], FILE * const stream) {
+	size_t i = 0;
+	char c = 0, s[BUFSIZ], *sp = s;
+	memset(s, '\0', sizeof(s));
+	while ((c = fgetc(stream)) != EOF && i < n && sp < s + BUFSIZ) {
+		if (isspace(c)) {
+			*sp = '\0';
+			args[i++] = strdup(s);
+			sp = s;
+			if (strcmp(args[i-1], "") == 0) {
+				free(args[i-1]);
+				args[i-1] = NULL;
+				i--;
+			}
+			if (c == '\n') {
+				break;
+			}
+		} else {
+			*sp++ = c;
+		}
+	}
+	return i;
+}
+
+int shellexec(size_t n, char * const args[n]) {
+	if (strcmp(args[0], "exit") == 0) {
+		run = false;
+		return 0;
+	}
+	pid_t pid = fork();
+	int status;
+	if (pid == 0) {
+		if (execvp(args[0], args) == -1) {
+			perror("jsh");
+		}
+		exit(EXIT_FAILURE);
+	} else if (pid < 0) {
+		perror("jsh");
+		exit(EXIT_FAILURE);
+	} else {
+		do {
+		  waitpid(pid, &status, WUNTRACED);
+		} while (!WIFEXITED(status) && !WIFSIGNALED(status));
+	}
+	return 0;
+}
+
diff --git a/src/cmd/jsh/makefile b/src/cmd/jsh/makefile
new file mode 100755
index 0000000..72d7d68
--- /dev/null
+++ b/src/cmd/jsh/makefile
@@ -0,0 +1,12 @@
+CFLAGS=-Wall -Werror
+
+build: jsh
+	@cp jsh $(PROROOT)/build/bin/jsh
+
+jsh: jsh.c
+	$(CC) $(CFLAGS) -o jsh jsh.c
+
+clean:
+	@rm -r jsh
+
+.PHONY: build clean
diff --git a/src/cmd/ls/ls.c b/src/cmd/ls/ls.c
new file mode 100755
index 0000000..a937457
--- /dev/null
+++ b/src/cmd/ls/ls.c
@@ -0,0 +1,78 @@
+/* TODO:
+ * - add flags
+ * - add option to print more file information
+ */
+#include <stdio.h>
+#include <sys/types.h>
+#include <dirent.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/stat.h>
+
+void dirwalk(DIR *);
+void error(char *);
+void printdirent(struct dirent *);
+void printfile(char *);
+
+/* print information about files and directories */
+int main(int argc, char **argv)
+{
+	DIR *dp;
+	if (argc == 1) {
+		if ((dp = opendir(".")) == NULL) {
+			perror("ls");
+			return -1;
+		}
+		dirwalk(dp);
+	} else if (argc == 2) {
+		if ((dp = opendir(argv[1])) == NULL) {
+			perror("ls");
+			return -1;
+		}
+		dirwalk(dp);
+	} else {
+		while (--argc > 0 && !ferror(stdout)) {
+			errno = 0;
+			if ((dp = opendir(*++argv)) == NULL) {
+				perror("ls");
+				continue;
+			}
+			dirwalk(dp);
+		}
+	}
+}
+
+/* dirwalk: read all the directory entries in a directory */
+void dirwalk(DIR *d)
+{
+	struct dirent *dir;
+	while ((dir = readdir(d)) != NULL) {
+		errno = 0;
+		if (strcmp(dir->d_name, ".") == 0 || strcmp(dir->d_name, "..") == 0)
+			continue;
+		printdirent(dir);
+	}
+	if (errno != 0) {
+		perror("ls");
+	}
+}
+
+/* printdirent: print a directory entry and any selected information */
+void printdirent(struct dirent *dir)
+{
+	printf("%s\n", dir->d_name);
+}
+
+/* printfile: print a file and any other selected information */
+void printfile(char *name)
+{
+	struct stat stbuf;
+	int e = stat(name, &stbuf);
+	if (e != 0) {
+		perror("ls");
+		return;
+	}
+	printf("%s\n", name);
+}
+
diff --git a/src/cmd/ls/makefile b/src/cmd/ls/makefile
new file mode 100755
index 0000000..d6a3c8d
--- /dev/null
+++ b/src/cmd/ls/makefile
@@ -0,0 +1,12 @@
+CFLAGS=-Wall -Werror
+
+build: ls
+	@cp ls $(PROROOT)/build/bin/ls
+
+ls: ls.c
+	$(CC) $(CFLAGS) -o ls ls.c
+
+clean:
+	@rm -r ls
+
+.PHONY: build clean
diff --git a/src/cmd/makefile b/src/cmd/makefile
index 52ddd59..481e827 100644
--- a/src/cmd/makefile
+++ b/src/cmd/makefile
@@ -1,4 +1,4 @@
-TOPTARGETS := all clean install
+TOPTARGETS := all build clean install
 
 SUBDIRS := $(wildcard */.)
 
diff --git a/src/cmd/pwd/makefile b/src/cmd/pwd/makefile
new file mode 100755
index 0000000..85f4d06
--- /dev/null
+++ b/src/cmd/pwd/makefile
@@ -0,0 +1,12 @@
+CFLAGS=-Wall -Werror
+
+build: pwd
+	@cp pwd $(PROROOT)/build/bin/pwd
+
+pwd: pwd.c
+	$(CC) $(CFLAGS) -o pwd pwd.c
+
+clean:
+	@rm -r pwd
+
+.PHONY: build clean
diff --git a/src/cmd/pwd/pwd.c b/src/cmd/pwd/pwd.c
new file mode 100755
index 0000000..d8c4c2a
--- /dev/null
+++ b/src/cmd/pwd/pwd.c
@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <errno.h>
+
+#define MAXLEN	1024
+
+/* print the current working directory */
+int main(void)
+{
+	char *cwd, i = 1;
+
+	do {
+		size_t size = i * MAXLEN;
+		cwd = (char *)malloc(size);
+		getcwd(cwd, size);
+		if (errno == ERANGE)
+			free((void *)cwd);
+	} while (errno == ERANGE && ++i < 10);
+
+	if (errno == ERANGE) {
+		fprintf(stderr, "pwd: directory name is too large\n");
+		return -1;
+	}
+
+	printf("%s\n", cwd);
+	free((void *)cwd);
+	return 0;
+}
+
diff --git a/src/makefile b/src/makefile
index 52ddd59..481e827 100644
--- a/src/makefile
+++ b/src/makefile
@@ -1,4 +1,4 @@
-TOPTARGETS := all clean install
+TOPTARGETS := all build clean install
 
 SUBDIRS := $(wildcard */.)