It will be useful if we can print out the last n lines instead of the last
10, just like tail.
There are examples:
tailf -n 5 file1
tailf --lines 10 file2
tailf -20 file3
Signed-off-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
---
tailf.1 | 14 +++++++++-----
tailf.c | 48 +++++++++++++++++++++++++++++++++---------------
2 files changed, 42 insertions(+), 20 deletions(-)
diff --git a/text-utils/tailf.1 b/text-utils/tailf.1
index ccce662..8bc53fc 100644
--- a/text-utils/tailf.1
+++ b/text-utils/tailf.1
@@ -26,7 +26,8 @@
.SH NAME
tailf \- follow the growth of a log file
.SH SYNOPSIS
-.BI tailf " file"
+.B tailf
+[\fIOPTION\fR] \fIfile\fR
.SH DESCRIPTION
.B tailf
will print out the last 10 lines of a file and then wait for the file to
@@ -40,10 +41,13 @@ does not occur periodically when no log activity is happening.
is extremely useful for monitoring log files on a laptop when logging is
infrequent and the user desires that the hard disk spin down to conserve
battery life.
-.SH BUGS
-An option could be provided to print out the last
-.I n
-lines instead of the last 10.
+.PP
+Mandatory arguments to long options are mandatory for short options too.
+.TP
+\fB\-n\fR, \fB\-\-lines\fR=\fIN\fR, \fB\-N\fR
+output the last
+.I N
+lines, instead of the last 10.
.SH AUTHOR
This program was written by Rik Faith (faith@xxxxxxx) and may be freely
distributed under the terms of the X11/MIT License. There is ABSOLUTELY
diff --git a/text-utils/tailf.c b/text-utils/tailf.c
index e10243f..3fbe849 100644
--- a/text-utils/tailf.c
+++ b/text-utils/tailf.c
@@ -31,8 +31,11 @@
#include <unistd.h>
#include <malloc.h>
#include <sys/stat.h>
+#include "errs.h"
#include "nls.h"
+#define DEFAULT_LINES 10
+
static size_t filesize(const char *filename)
{
struct stat sb;
@@ -50,9 +53,7 @@ static void tailf(const char *filename, int lines)
int i;
if (!(str = fopen(filename, "r"))) {
- fprintf(stderr, _("Cannot open \"%s\" for read\n"), filename);
- perror("");
- exit(1);
+ err(EXIT_FAILURE, "Cannot open %s for read", filename);
}
buffer = malloc(lines * sizeof(*buffer));
@@ -84,28 +85,45 @@ int main(int argc, char **argv)
FILE *str;
const char *filename;
int count;
+ int lines = DEFAULT_LINES;
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
- if (argc != 2) {
- fprintf(stderr, _("Usage: tailf logfile\n"));
- exit(1);
- }
+ argc--;
+ argv++;
- filename = argv[1];
+ for (; argc > 0 && argv[0][0] == '-'; argc--, argv++) {
+ if (!strcmp(*argv, "-n") || !strcmp(*argv, "--lines")) {
+ argc--;
+ argv++;
+ if (argc > 0 && (lines = atoi(argv[0])) <= 0)
+ errx(EXIT_FAILURE, _("Invalid number of lines"));
+ }
+ else if (isdigit(argv[0][1])) {
+ if ((lines = atoi(*argv + 1)) <= 0)
+ errx(EXIT_FAILURE, _("Invalid number of lines"));
+ }
+ else
+ errx(EXIT_FAILURE, _("Invalid option"));
+ }
+
+ if (argc != 1) {
+ fprintf(stderr, _("Usage: tailf [-n N | -N] logfile\n"));
+ exit(EXIT_FAILURE);
+ }
- tailf(filename, 10);
+ filename = argv[0];
+
+ tailf(filename, lines);
for (osize = filesize(filename);;) {
nsize = filesize(filename);
if (nsize != osize) {
- if (!(str = fopen(filename, "r"))) {
- fprintf(stderr, _("Cannot open \"%s\" for read\n"), filename);
- perror(argv[0]);
- exit(1);
- }
+ if (!(str = fopen(filename, "r")))
+ err(EXIT_FAILURE, "Cannot open %s for read", filename);
+
if (!fseek(str, osize, SEEK_SET))
while ((count = fread(buffer, 1, sizeof(buffer), str)) > 0)
fwrite(buffer, 1, count, stdout);
@@ -115,5 +133,5 @@ int main(int argc, char **argv)
}
usleep(250000); /* 250mS */
}
- return 0;
+ return EXIT_SUCCESS;
}
---
-
To unsubscribe from this list: send the line "unsubscribe util-linux-ng" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
