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authorzlg <zlg@zlg.space>2013-08-29 06:29:09 -0500
committerzlg <zlg@zlg.space>2013-08-29 06:29:09 -0500
commit6484527cec80136b09288abb1583046f5b776411 (patch)
treec3a715b426801ec72a82a92abea7cd9687aa59d7 /ch5
parentSolve Exercise 5-2: getfloat() (diff)
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Solve Exercise 5-3: pointer-powered strcat()
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-rw-r--r--ch5/5-03_strcatp.c42
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diff --git a/ch5/5-03_strcatp.c b/ch5/5-03_strcatp.c
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+#include <stdio.h>
+
+/* The C Programming Language, 2nd Edition
+ *
+ * Exercise 5-3: Write a pointer version of the function strcat that we showed
+ * in Chapter 2: strcat(s,t) copies the string t to the end of s.
+ *
+ * Answer: Pay careful attention to the passage before this exercise; there's
+ * a difference between a character array and a pointer to a string constant.
+ * The major difference is you can modify the contents of a character array.
+ * String constants, like other constants, can't be modified. This practically
+ * requires that the first argument to strcatp is a character array.
+ *
+ * When working with pointers, details seem to be of utmost importance.
+ *
+ * Thanks to Chris and dagle from Freenode's ##c for their input on
+ * improving the code.
+ */
+
+#define ALLOC 80
+
+void strcatp(char *s, char *t);
+
+int main(void) {
+ char foo[ALLOC] = "This is amazing!";
+ char *bar = " Pointers for everyone!";
+ strcatp(foo, bar);
+ printf("%s\n", foo);
+ return 0;
+}
+
+/* strcat: copy t into s; s must be large enough */
+void strcatp(char *s, char *t) {
+ while (*s != '\0') {
+ s++;
+ }
+ /* Doing this without checking a buffer means it may screw up memory.
+ * It's the programmer's duty to ensure this doesn't happen, not the
+ * function's.
+ */
+ while ((*s++ = *t++));
+}