Document -n/-c +N feature

That should make inotail POSIX tail compatible

2 files changed, 14 insertions, 9 deletions

diff --git a/inotail.1 b/inotail.1
index a623f0a..9145dec 100644
--- a/inotail.1
+++ b/inotail.1
@@ -31,13 +31,15 @@ be in the future.
 .SH OPTIONS
 .TP
 .B \-c \fIN\fR, \fB\-\-bytes\fR=\fIN\fR
-output the last N bytes
+output the last N bytes. If the first character of N is a '+', begin printing
+with the Nth character from the start of each file.
 .TP
 .B \-f, \fB\-\-follow
 keep the file(s) open and print appended data as the file grows
 .TP
 .B \-n \fIN\fR, \fB\-\-lines\fR=\fIN\fR
-output the last N lines (default: 10)
+output the last N lines (default: 10) If the first character of N is a '+',
+begin printing with  with the Nth line from the start of each file.
 .TP
 .B \-v, \fB\-\-verbose
 print headers with file names
diff --git a/inotail.c b/inotail.c
index e07f118..fefde0d 100644
--- a/inotail.c
+++ b/inotail.c
@@ -64,13 +64,16 @@ static const struct option long_opts[] = {
 
 static void usage(const int status)
 {
-	fprintf(stderr, "Usage: %s [OPTION]... [FILE]...\n\n", PROGRAM_NAME);
-	fprintf(stderr, "  -c N, --bytes=N    output the last N bytes\n");
-	fprintf(stderr, "  -f,   --follow     output as the file grows\n");
-	fprintf(stderr, "  -n N, --lines=N    output the last N lines (default: %d)\n", DEFAULT_N_LINES);
-	fprintf(stderr, "  -v,   --verbose    print headers with file names\n");
-	fprintf(stderr, "  -h,   --help       show this help and exit\n");
-	fprintf(stderr, "  -V,   --version    show version and exit\n");
+	fprintf(stderr, "Usage: %s [OPTION]... [FILE]...\n\n"
+			"  -c N, --bytes=N    output the last N bytes\n"
+			"  -f,   --follow     output as the file grows\n"
+			"  -n N, --lines=N    output the last N lines (default: %d)\n"
+			"  -v,   --verbose    print headers with file names\n"
+			"  -h,   --help       show this help and exit\n"
+			"  -V,   --version    show version and exit\n\n"
+			"If the first character of N (the number of bytes or lines) is a `+',\n"
+			"begin printing with the Nth item from the start of each file, otherwise,\n"
+			"print the last N items in the file.\n", PROGRAM_NAME, DEFAULT_N_LINES);
 
 	exit(status);
 }