Add -b to change which byte is tested

3 files changed, 39 insertions, 10 deletions

diff --git a/README b/README
index a5a6b5c..91f6cca 100644
--- a/README
+++ b/README
@@ -4,7 +4,7 @@ NAME
      holes – find runs of zero bytes
 
 SYNOPSIS
-     holes [-n minlen] [files ...]
+     holes [-b byte] [-n minlen] [files ...]
 
 DESCRIPTION
      holes looks for runs of zero bytes (a.k.a. holes) in the specified input
@@ -12,8 +12,15 @@ DESCRIPTION
      hexadecimal) as well as the lengths (in decimal).  When multiple input
      files are specified, holes prefixes each line with the file name.
 
-     By default, only holes of at least 64 bytes are reported.  This can be
-     changed using the -n option.
+     The options are as follows:
+
+     -b byte
+             Count runs of byte, a number between 0 and 255, instead of zero
+             bytes.
+
+     -n minlen
+             Change minimum size of holes reported.  By default, only holes of
+             at least 64 bytes are reported.
 
 EXIT STATUS
      The holes utility exits 0 on success, and >0 if an error occurs.
diff --git a/holes.1 b/holes.1
index 6d24b08..2edbaf9 100644
--- a/holes.1
+++ b/holes.1
@@ -6,6 +6,7 @@
 .Nd find runs of zero bytes
 .Sh SYNOPSIS
 .Nm
+.Op Fl b Ar byte
 .Op Fl n Ar minlen
 .Op Ar files\ ...
 .Sh DESCRIPTION
@@ -18,11 +19,18 @@ When multiple input files are specified,
 .Nm
 prefixes each line with the file name.
 .Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl b Ar byte
+Count runs of
+.Ar byte ,
+a number between 0 and 255,
+instead of zero bytes.
+.It Fl n Ar minlen
+Change minimum size of holes reported.
 By default,
 only holes of at least 64 bytes are reported.
-This can be changed using the
-.Fl n
-option.
+.El
 .Sh EXIT STATUS
 .Ex -std
 .Sh SEE ALSO
diff --git a/holes.c b/holes.c
index c618a8e..41fc50c 100644
--- a/holes.c
+++ b/holes.c
@@ -7,7 +7,8 @@
 #include <unistd.h>
 
 ssize_t minlen = 64;
-int ret;
+char byte = 0;
+int ret = 0;
 char *argv0;
 
 void
@@ -18,7 +19,7 @@ holes(FILE *input, char *filename)
 	int ch;
 
 	while ((ch = getc_unlocked(input)) != EOF) {
-		if (ch == 0) {
+		if (ch == byte) {
 			run++;
 		} else {
 			if (run >= minlen) {
@@ -49,12 +50,24 @@ int
 main(int argc, char *argv[])
 {
 	int c, i;
+	long b;
 	char *e;
 
 	argv0 = argv[0];
 
-	while ((c = getopt(argc, argv, "n:")) != -1)
+	while ((c = getopt(argc, argv, "b:n:")) != -1)
 		switch(c) {
+		case 'b':
+			errno = 0;
+			b = strtol(optarg, &e, 0);
+			if (errno != 0 || *e || b < 0 || b > 256) {
+				fprintf(stderr,
+				    "%s: can't parse byte '%s'.\n",
+				    argv0, optarg);
+				exit(2);
+			}
+			byte = b;
+			break;
                 case 'n':
 			errno = 0;
 			minlen = strtoll(optarg, &e, 0);
@@ -73,7 +86,8 @@ main(int argc, char *argv[])
 			break;
                 default:
                         fprintf(stderr,
-			    "Usage: %s [-n MINLEN] [FILES...]\n", argv0);
+			    "Usage: %s [-b BYTE] [-n MINLEN] [FILES...]\n",
+			    argv0);
 			exit(2);
 		}