Tweak NULL-pointer checks

Use !p and p when comparing pointers as opposed to explicit
checks against NULL.  This is generally easier to read.

cksum.c

@@ -114,7 +114,7 @@ cksum(FILE *fp, const char *s)
 		ck = (ck << 8) ^ crctab[(ck >> 24) ^ (i & 0xFF)];
 
 	printf("%"PRIu32" %lu", ~ck, (unsigned long)len);
-	if (s != NULL)
+	if (s)
 		printf(" %s", s);
 	putchar('\n');
 }

readlink.c

@@ -43,7 +43,7 @@ main(int argc, char *argv[])
 		return 1;
 
 	if (fflag) {
-		if (realpath(argv[0], buf) == NULL)
+		if (!realpath(argv[0], buf))
 			exit(1);
 	} else {
 		if ((n = readlink(argv[0], buf, sizeof(buf) - 1)) < 0)

sort.c

@@ -238,12 +238,12 @@ skipblank(char *s)
 static char *
 nextcol(char *s)
 {
-	if (fieldsep == NULL) {
+	if (!fieldsep) {
 		s = skipblank(s);
 		while(*s && !isblank(*s))
 			s++;
 	} else {
-		if (strchr(s, *fieldsep) == NULL)
+		if (!strchr(s, *fieldsep))
 			s = strchr(s, '\0');
 		else
 			s = strchr(s, *fieldsep) + 1;
@@ -274,11 +274,11 @@ columns(char *line, const struct keydef *kd)
 		else
 			end = nextcol(end);
 	} else {
-		if ((end = strchr(line, '\n')) == NULL)
+		if (!(end = strchr(line, '\n')))
 			end = strchr(line, '\0');
 	}
 
-	if ((res = strndup(start, end - start)) == NULL)
+	if (!(res = strndup(start, end - start)))
 		enprintf(2, "strndup:");
 	return res;
 }

split.c

@@ -36,11 +36,11 @@ main(int argc, char *argv[])
 	case 'b':
 		always = 1;
 		tmp = ARGF();
-		if (tmp == NULL)
+		if (!tmp)
 			break;
 
 		size = strtoull(tmp, &end, 10);
-		if (*end == '\0')
+		if (!*end)
 			break;
 		switch (toupper((int)*end)) {
 		case 'K':

uniq.c

@@ -62,7 +62,7 @@ main(int argc, char *argv[])
 static void
 uniqline(char *l)
 {
-	int linesequel = ((l == NULL) || (prevline == NULL))
+	int linesequel = (!l || !prevline)
 		? l == prevline
 		: !strcmp(l, prevline);
 
@@ -71,7 +71,7 @@ uniqline(char *l)
 		return;
 	}
 
-	if (prevline != NULL) {
+	if (prevline) {
 		if ((prevlinecount == 1 && !dflag) ||
 		    (prevlinecount != 1 && !uflag)) {
 			printf(countfmt, prevlinecount);

util/crypt.c

@@ -46,7 +46,7 @@ cryptcheck(char *sumfile, int argc, char *argv[],
 	int r, nonmatch = 0, formatsucks = 0, noread = 0, ret = 0;
 	size_t bufsiz = 0;
 
-	if (sumfile == NULL)
+	if (!sumfile)
 		cfp = stdin;
 	else if (!(cfp = fopen(sumfile, "r")))
 		eprintf("fopen %s:", sumfile);
@@ -81,7 +81,7 @@ cryptcheck(char *sumfile, int argc, char *argv[],
 		}
 		fclose(fp);
 	}
-	if (sumfile != NULL)
+	if (sumfile)
 		fclose(cfp);
 	free(line);
 	if (formatsucks > 0) {
@@ -111,7 +111,7 @@ cryptmain(int argc, char *argv[],
 		mdprint(md, "<stdin>", sz);
 	} else {
 		for (; argc > 0; argc--) {
-			if ((fp = fopen(*argv, "r")) == NULL) {
+			if (!(fp = fopen(*argv, "r"))) {
 				weprintf("fopen %s:", *argv);
 				ret = 1;
 				continue;

util/getlines.c

@@ -17,7 +17,7 @@ getlines(FILE *fp, struct linebuf *b)
 		if (++b->nlines > b->capacity) {
 			b->capacity += 512;
 			nline = realloc(b->lines, b->capacity * sizeof(*b->lines));
-			if (nline == NULL)
+			if (!nline)
 				eprintf("realloc:");
 			b->lines = nline;
 		}

uudecode.c

@@ -40,14 +40,14 @@ main(int argc, char *argv[])
 
 	if (argc == 0) {
 		parseheader(stdin, "<stdin>", "begin ", &mode, &fname);
-		if ((nfp = parsefile(fname)) == NULL)
+		if (!(nfp = parsefile(fname)))
 			eprintf("fopen %s:", fname);
 		uudecode(stdin, nfp);
 	} else {
-		if ((fp = fopen(argv[0], "r")) == NULL)
+		if (!(fp = fopen(argv[0], "r")))
 			eprintf("fopen %s:", argv[0]);
 		parseheader(fp, argv[0], "begin ", &mode, &fname);
-		if ((nfp = parsefile(fname)) == NULL)
+		if (!(nfp = parsefile(fname)))
 			eprintf("fopen %s:", fname);
 		uudecode(fp, nfp);
 	}
@@ -93,18 +93,18 @@ parseheader(FILE *fp, const char *s, const char *header, mode_t *mode, char **fn
 	char *p, *q;
 	size_t n;
 
-	if (fgets(bufs, sizeof(bufs), fp) == NULL)
+	if (!fgets(bufs, sizeof(bufs), fp))
 		if (ferror(fp))
 			eprintf("%s: read error:", s);
 	if (bufs[0] == '\0' || feof(fp))
 		eprintf("empty or nil header string\n");
-	if ((p = strchr(bufs, '\n')) == NULL)
+	if (!(p = strchr(bufs, '\n')))
 		eprintf("header string too long or non-newline terminated file\n");
 	p = bufs;
 	if (strncmp(bufs, header, strlen(header)) != 0)
 		eprintf("malformed header prefix\n");
 	p += strlen(header);
-	if ((q = strchr(p, ' ')) == NULL)
+	if (!(q = strchr(p, ' ')))
 		eprintf("malformed mode string in header\n");
 	*q++ = '\0';
 	/* now mode should be null terminated, q points to fname */