cat(1): simplify argv processing loops

cook_args() and raw_args() do some peculiar things in order to avoid
calling cook_buf() and raw_cat(), respectively, in more than one
place.  The result is a convoluted.  If we isolate the special cases
from the normal case and just call these functions in multiple places
the loops will be easier to read.

Three things:

1. Pull the no-args case out of the loop.  If *argv is NULL when we
   get into the argv processing function we just want to operate on
   the standard input and return early.  It makes no sense to handle
   this case *in* the loop.

2. Isolate the "-" case from the filename case.  If *argv is "-" we want
   to operate on the standard input.  We can then do any stdin-specific
   cleanup within the same branch, which makes it easier to understand
   both the "-" case and the normal filename case.  This also allows us
   to remove the 'filename' intermediate variable from both argv processing
   functions.

3. While we're here, use a for-loop and iterate argv in the loop header.
   Now argv is incremented in one place.

ok martijn@

1 files changed, 36 insertions, 39 deletions

diff --git a/bin/cat/cat.c b/bin/cat/cat.c
index a602e0f1581..fa35136a250 100644
--- a/bin/cat/cat.c
+++ b/bin/cat/cat.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cat.c,v 1.28 2020/12/03 22:37:12 cheloha Exp $	*/
+/*	$OpenBSD: cat.c,v 1.29 2020/12/04 01:42:05 cheloha Exp $	*/
 /*	$NetBSD: cat.c,v 1.11 1995/09/07 06:12:54 jtc Exp $	*/
 
 /*
@@ -107,29 +107,27 @@ main(int argc, char *argv[])
 void
 cook_args(char **argv)
 {
-	char *filename;
 	FILE *fp;
 
-	fp = stdin;
-	filename = "stdin";
-	do {
-		if (*argv) {
-			if (!strcmp(*argv, "-"))
-				fp = stdin;
-			else if ((fp = fopen(*argv, "r")) == NULL) {
-				warn("%s", *argv);
-				rval = 1;
-				++argv;
-				continue;
-			}
-			filename = *argv++;
+	if (*argv == NULL) {
+		cook_buf(stdin, "stdin");
+		return;
+	}
+
+	for (; *argv != NULL; argv++) {
+		if (!strcmp(*argv, "-")) {
+			cook_buf(stdin, "stdin");
+			clearerr(stdin);
+			continue;
+		}
+		if ((fp = fopen(*argv, "r")) == NULL) {
+			warn("%s", *argv);
+			rval = 1;
+			continue;
 		}
-		cook_buf(fp, filename);
-		if (fp == stdin)
-			clearerr(fp);
-		else
-			(void)fclose(fp);
-	} while (*argv);
+		cook_buf(fp, *argv);
+		fclose(fp);
+	}
 }
 
 void
@@ -198,27 +196,26 @@ cook_buf(FILE *fp, const char *filename)
 void
 raw_args(char **argv)
 {
-	char *filename;
 	int fd;
 
-	fd = fileno(stdin);
-	filename = "stdin";
-	do {
-		if (*argv) {
-			if (!strcmp(*argv, "-"))
-				fd = fileno(stdin);
-			else if ((fd = open(*argv, O_RDONLY, 0)) == -1) {
-				warn("%s", *argv);
-				rval = 1;
-				++argv;
-				continue;
-			}
-			filename = *argv++;
+	if (*argv == NULL) {
+		raw_cat(fileno(stdin), "stdin");
+		return;
+	}
+
+	for (; *argv != NULL; argv++) {
+		if (!strcmp(*argv, "-")) {
+			raw_cat(fileno(stdin), "stdin");
+			continue;
+		}
+		if ((fd = open(*argv, O_RDONLY, 0)) == -1) {
+			warn("%s", *argv);
+			rval = 1;
+			continue;
 		}
-		raw_cat(fd, filename);
-		if (fd != fileno(stdin))
-			(void)close(fd);
-	} while (*argv);
+		raw_cat(fd, *argv);
+		close(fd);
+	}
 }
 
 void