Completed exercise 5-05

Completed exercise 5-05 - versions of strncpy(), strncmp(), and
strncat()

Author: ptdecker

Makefile

@@ -5,7 +5,6 @@ SUBDIRS = src
 
 all:
 	@for i in $(SUBDIRS); do \
-		echo "make all in $$i..."; \
 		cd $$i; \
 		make all; \
 		cd ..; \
@@ -17,4 +16,3 @@ clean:
 		make clean; \
 		cd ..; \
 	done
-	rm -f $(ODIR)/*.o

README.md

@@ -71,7 +71,7 @@ Kernighan and Ritchie The C Programming Language Code Examples
 * 4-08 - singlegetch.c:        Implements getch() and ungetch() that support just a single char buffer
 * 4-09 - ungetseof.c:          Implements getch(), ungetch(), and ungets() in a maner supporting EOF
 * 4-10 - rpncalc4-10/*.c:      RPN Calculator (rpncalc5) based upon whole line handling
-* 4-11 - rpncalc4-11/*.c:      RPN calculator (rpncacl6) that uses 'static' to negate needing ungetch()
+* 4-11 - rpncalc4-11/*.c:      RPN calculator (rpncalc6) that uses 'static' to negate needing ungetch()
 * 4-12 - itoarecursive.c:      A recursive implementation of itoa()
 * 4-13 - reverserecursive.c:   A recursive implementation of reverse()
 * 4-14 - swapmacro.c:          A version of reverse() that uses a macro for swaping two values

src/chapter05/strnfunc/Makefile

@@ -6,8 +6,8 @@ CFLAGS = -std=c99 -Wall -g -I.
 LINT = splint
 LINTFLAGS = -compdef +quiet +skip-sys-headers +charintliteral +charint -shadow -preproc
 DEPS =
-_OBJ = strncat.o
-_BIN = strncat
+_OBJ = strncat.o strncopy.o strncmp.o
+_BIN = strncat strncopy strncmp
 
 OBJ = $(patsubst %,$(ODIR)/%,$(_OBJ))
 
@@ -32,6 +32,14 @@ strncat: $(ODIR)/strncat.o
 	$(CC) $(CFLAGS) $^ -o $@
 	cp -v $@ $(BIN)/$@
 
+strncopy: $(ODIR)/strncopy.o
+	$(CC) $(CFLAGS) $^ -o $@
+	cp -v $@ $(BIN)/$@
+
+strncmp: $(ODIR)/strncmp.o
+	$(CC) $(CFLAGS) $^ -o $@
+	cp -v $@ $(BIN)/$@
+
 $(ODIR)/%.o: %.c $(DEPS)
 	mkdir -pv $(ODIR)
 	$(CC) $(CFLAGS) -c -o $@ $<

src/chapter05/strnfunc/strncmp.c

@@ -0,0 +1,39 @@
+/*
+ * strncmp.c
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAXSTR 1000
+
+/*
+ * strncmp(): Compares the fist 'count' characters of 'source' string to 'dest' string.
+ *
+ * NOTE: A terminating '\0' *is not* appended!
+ * 
+ * NOTE: It is assumed that 'leftstring' is big enough to hold the combined text
+ */
+
+static int strncmp(char *s1, char *s2, size_t count) {
+    for ( ; --count > 0 && *s1 == *s2; s1++, s2++)
+        if (*s1 == '\0')
+            return 0;
+    return *s1 - *s2;
+}
+
+
+int main(void) {
+
+    char s1[MAXSTR] = "aaa";
+    char s2[MAXSTR] = "aba";
+    char s3[MAXSTR] = "abb";
+    char s4[MAXSTR] = "aca";
+
+    printf("Comparing the first 2 characters of \"%s\" to \"%s\" results in: %d\n", s1, s2, strncmp(s1, s2, 2));
+    printf("Comparing the first 2 characters of \"%s\" to \"%s\" results in: %d\n", s3, s2, strncmp(s3, s2, 2));
+    printf("Comparing the first 2 characters of \"%s\" to \"%s\" results in: %d\n", s4, s2, strncmp(s4, s2, 2));
+
+    exit(EXIT_SUCCESS);
+}

src/chapter05/strnfunc/strncopy.c

@@ -0,0 +1,37 @@
+/*
+ * strncopy.c
+ */
+
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define MAXSTR 1000
+
+/*
+ * strncopy(): Copies at most 'count' characters of 'source' string to 'dest' string.
+ *
+ * NOTE: A terminating '\0' *is not* appended!
+ * 
+ * NOTE: It is assumed that 'leftstring' is big enough to hold the combined text
+ */
+
+static void strncopy(char *dest, char *source, size_t count) {
+    while (count-- > 0 && (*dest++ = *source++) != '\0')
+        ; // Empty
+}
+
+
+int main(void) {
+
+    char string1[MAXSTR] = "Overwrite me!!";
+    char string2[MAXSTR] = "I am the destoryer!";
+
+    printf("Copies the first 4 characters of \"%s\" to the string currently containing \"%s\" results in: ", string2, string1);
+
+    strncopy(string1, string2, 4);
+
+    printf("\"%s\"\n", string1);
+
+    exit(EXIT_SUCCESS);
+}