From 0861d76717ceaff31bf8172e6fa117c8f03d536e Mon Sep 17 00:00:00 2001
From: John Ankarstrom <john@ankarstrom.se>
Date: Tue, 6 Jul 2021 21:39:59 +0200
Subject: Add -d flag

---
 build.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 64 insertions(+), 23 deletions(-)

diff --git a/build.c b/build.c
index e69164c..230dea9 100644
--- a/build.c
+++ b/build.c
@@ -4,21 +4,37 @@
 #include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 #define USAGE "usage: %s file [...]\n", argv[0]
 
+extern char *optarg;
+extern int optind;
+
 int
 main(int argc, char *argv[])
 {
 	char *b, *bb, *bbb, buf[1024], *cmd[32], dep[1024], *t, *tt, tgt[64];
 	FILE *fp;
-	int i, icmd, j, max;
+	int c, dflag, i, icmd, j, max;
 	struct stat sb, ssb;
 
 	tgt[0] = dep[0] = 0;
 
 	/* process arguments */
-	if (argc-1 == 0) {
+	dflag = 0;
+	while ((c = getopt(argc, argv, "d")) != -1)
+		switch (c) {
+		case 'd':
+			dflag++;
+			break;
+		default:
+			fprintf(stderr, USAGE);
+			return 1;
+		}
+	argc -= optind;
+	argv += optind;
+	if (argc == 0) {
 		fprintf(stderr, USAGE);
 		return 1;
 	}
@@ -30,7 +46,7 @@ main(int argc, char *argv[])
 	}
 
 	/* process each file */
-	for (i = 1, icmd = 0; i < argc; i++, icmd = 0) {
+	for (i = icmd = 0; i < argc; i++, icmd = 0) {
 		fp = fopen(argv[i], "r");
 		if (!fp) err(1, "fopen");
 
@@ -55,12 +71,21 @@ main(int argc, char *argv[])
 						strncpy(tgt,b+1,sizeof(tgt)-1);
 
 					}
+
+					if (dflag < 3) continue;
+					fprintf(stderr,
+						"%s: command line '%s'\n",
+						argv[i], buf);
 					continue;
 				}
 
-				/* depend line */
+				/* depends line */
 				if (*(b+1) == '%' && *(b+2) == ' ') {
 					strncpy(dep, b+3, sizeof(dep)-1);
+					if (dflag < 3) continue;
+					fprintf(stderr,
+						"%s: depends line '%s'\n",
+						argv[i], buf);
 					continue;
 				}
 			}
@@ -83,32 +108,48 @@ main(int argc, char *argv[])
 			err(1, t);
 		if (stat(argv[i], &sb))
 			err(1, argv[i]);
-		if (sb.st_mtime > ssb.st_mtime)
+		if (sb.st_mtime > ssb.st_mtime) {
+			if (dflag)
+				fprintf(stderr, "%s: building because "
+					"%s is modified\n", argv[i], argv[i]);
 			goto build;
+		}
+
+		if (!*dep)
+			goto uptodate;
 
 		/* compare dependencies > target */
-		if (*dep) {
-			for (t = dep; *t; t++)
-				if (!isspace(*t)) break;
-			for (j = 0; t[j]; j++) {
-				if (isspace(t[j]) || t[j+1] == 0) {
-					tt = strdup(t);
-					tt[j+(t[j+1]==0)] = 0;
-
-					if (stat(tt, &sb))
-						err(1, tt);
-					free(tt);
-					if (sb.st_mtime > ssb.st_mtime)
-						goto build;
-
-					for (; t[j]; j++)
-						if (!isspace(t[j])) break;
-					t += j;
-					j = 0;
+		for (t = dep; *t; t++)
+			if (!isspace(*t)) break;
+		for (j = 0; t[j]; j++) {
+			if (isspace(t[j]) || t[j+1] == 0) {
+				tt = strdup(t);
+				tt[j+(t[j+1]==0)] = 0;
+
+				if (dflag > 1)
+					fprintf(stderr, "%s: depend '%s'\n",
+						argv[i], tt);
+
+				if (stat(tt, &sb))
+					err(1, tt);
+				free(tt);
+				if (sb.st_mtime > ssb.st_mtime) {
+					if (dflag)
+						fprintf(stderr,
+							"%s: building because "
+							"%s is modified\n",
+							argv[i], tt);
+					goto build;
 				}
+
+				for (; t[j]; j++)
+					if (!isspace(t[j])) break;
+				t += j;
+				j = 0;
 			}
 		}
 
+uptodate:
 		fprintf(stderr, "%s: already up-to-date\n", argv[i]);
 		goto done;
 
-- 
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