Implement cp -f

cp.1

@@ -17,6 +17,9 @@ copies a given file, naming it the given name.  If multiple files are listed
 they will be copied into the given directory.
 .SH OPTIONS
 .TP
+.B \-f
+if an existing destination file cannot be opened, remove it and try again.
+.TP
 .B \-R
 equivalent to -r.
 .TP

cp.c

@@ -8,7 +8,7 @@
 static void
 usage(void)
 {
-	eprintf("usage: %s [-Rr] source... dest\n", argv0);
+	eprintf("usage: %s [-fRr] source... dest\n", argv0);
 }
 
 int
@@ -17,6 +17,9 @@ main(int argc, char *argv[])
 	struct stat st;
 
 	ARGBEGIN {
+	case 'f':
+		cp_fflag = true;
+		break;
 	case 'R':
 	case 'r':
 		cp_rflag = true;

fs.h

@@ -1,6 +1,7 @@
 /* See LICENSE file for copyright and license details. */
 #include <stdbool.h>
 
+extern bool cp_fflag;
 extern bool cp_rflag;
 extern bool rm_fflag;
 extern bool rm_rflag;

util/cp.c

@@ -12,6 +12,7 @@
 #include "../text.h"
 #include "../util.h"
 
+bool cp_fflag = false;
 bool cp_rflag = false;
 
 int
@@ -62,8 +63,12 @@ cp(const char *s1, const char *s2)
 	if(!(f1 = fopen(s1, "r")))
 		eprintf("fopen %s:", s1);
 
-	if(!(f2 = fopen(s2, "w")))
-		eprintf("fopen %s:", s2);
+	if(!(f2 = fopen(s2, "w"))) {
+		if (cp_fflag == true)
+			unlink(s2);
+		if (!(f2 = fopen(s2, "w")))
+			eprintf("fopen %s:", s2);
+	}
 
 	concat(f1, s1, f2, s2);
 	fchmod(fileno(f2), st.st_mode);

util/fnck.c

@@ -18,4 +18,3 @@ fnck(const char *a, const char *b, int (*fn)(const char *, const char *))
 	if(fn(a, b) == -1)
 		eprintf("%s -> %s:", a, b);
 }
-