xargs: fix -I SUBSTR behaviour

function                                             old     new   delta
process_stdin_with_replace                           165     204     +39

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

findutils/xargs.c

@@ -80,9 +80,11 @@
 /* This is a NOEXEC applet. Be very careful! */
 
 
-//#define dbg_msg(...) bb_error_msg(__VA_ARGS__)
-#define dbg_msg(...) ((void)0)
-
+#if 0
+# define dbg_msg(...) bb_error_msg(__VA_ARGS__)
+#else
+# define dbg_msg(...) ((void)0)
+#endif
 
 #ifdef TEST
 # ifndef ENABLE_FEATURE_XARGS_SUPPORT_CONFIRMATION
@@ -466,9 +468,18 @@ static char* FAST_FUNC process_stdin_with_replace(int n_max_chars, int n_max_arg
 
 	while (1) {
 		int c = getchar();
+		if (p == buf) {
+			if (c == EOF)
+				goto ret; /* last line is empty, return "" */
+			if (c == G.eol_ch)
+				continue; /* empty line, ignore */
+			/* Skip leading whitespace of each line: try
+			 * echo -e ' \t\v1 2 3 ' | xargs -I% echo '[%]'
+			 */
+			if (ISSPACE(c))
+				continue;
+		}
 		if (c == EOF || c == G.eol_ch) {
-			if (p == buf)
-				goto ret; /* empty line */
 			c = '\0';
 		}
 		*p++ = c;

testsuite/xargs.tests

@@ -61,4 +61,12 @@ testing "xargs -n2" \
 
 SKIP=
 
+optional FEATURE_XARGS_SUPPORT_QUOTES
+testing "xargs -I skips empty lines and leading whitespace" \
+	"xargs -I% echo '[%]'" \
+	"[2]\n[4]\n[6 6 ]\n[7]\n" \
+	"" " \n2\n\n4\n\n 6 6 \n \v \t 7\n\t\n\v\n"
+
+SKIP=
+
 exit $FAILCOUNT