initial release.master

6 files changed, 334 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..c478614
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+.hg/
+.hgignore
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..35ac87d
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,39 @@
+CC=cc
+CFLAGS=-Wall -Wno-missing-braces -Wno-parentheses -Wno-switch -Wno-pointer-to-int-cast -fno-diagnostics-color -ggdb -c -O2
+LDFLAGS=-static
+O=o
+BIN=$(HOME)/bin
+
+TARG=logwatch
+OFILES=\
+	main.$O\
+
+LIBS=\
+	libutf/libutf.a\
+
+HFILES=\
+	args.h\
+	libutf/utf.h\
+
+.PHONY: all clean
+all: $(TARG)
+
+%.$O: %.c
+	$(CC) $(CFLAGS) $<
+
+$(OFILES): $(HFILES)
+
+$(TARG): $(OFILES)
+	$(CC) -o $@ $(OFILES) $(LIBS) $(LDFLAGS)
+
+install: $(TARG)
+	cp $(TARG) $(BIN)/
+
+uninstall:
+	rm -f $(BIN)/$(TARG)
+
+man:
+	groff -man $(TARG).8.man | ps2pdf - >$(TARG).8.pdf
+
+clean:
+	rm $(TARG) *.o *.pdf
diff --git a/args.h b/args.h
new file mode 100644
index 0000000..f7e3d5f
--- /dev/null
+++ b/args.h
@@ -0,0 +1,22 @@
+extern char *argv0;
+#define SET(x)          ((x)=0)
+#define USED(x)         if(x);else
+#define	ARGBEGIN	for((argv0? 0: (argv0=*argv)),argv++,argc--;\
+			    argv[0] && argv[0][0]=='-' && argv[0][1];\
+			    argc--, argv++) {\
+				char *_args, *_argt;\
+				Rune _argc;\
+				_args = &argv[0][1];\
+				if(_args[0]=='-' && _args[1]==0){\
+					argc--; argv++; break;\
+				}\
+				_argc = 0;\
+				while(*_args && (_args += chartorune(&_argc, _args)))\
+				switch(_argc)
+#define	ARGEND		SET(_argt);USED(_argt); USED(_argc); USED(_args);}USED(argv); USED(argc);
+#define	ARGF()		(_argt=_args, _args="",\
+				(*_argt? _argt: argv[1]? (argc--, *++argv): 0))
+#define	ARGC()		_argc
+
+#define	EARGF(x)		(_argt=_args, _args="",\
+				(*_argt? _argt: argv[1]? (argc--, *++argv): (x, (char*)0)))
diff --git a/logwatch.8.man b/logwatch.8.man
new file mode 100644
index 0000000..9613f5f
--- /dev/null
+++ b/logwatch.8.man
@@ -0,0 +1,41 @@
+.TH LOGWATCH 8
+.SH NAME
+logwatch \- log file stalker
+.SH SYNOPSIS
+.PP
+.B logwatch
+[
+.B -d
+] [
+.B -t
+.I perc
+]
+.I logfile
+.SH DESCRIPTION
+.I logwatch
+uses
+.I inotify (7)
+watches to monitor changes in a specific
+.IR logfile .
+It also monitors its parent directory, so it can track local movements (e.g. log rotations).
+If the
+.I logfile
+exceeds an established disk quota, it is truncated to half its size, keeping the latest data.
+.PP
+The flags are:
+.TP
+.B d
+Enable debugging output.
+.TP
+.B t
+Sets a percentage
+.I perc
+for the disk usage threshold the file cannot exceed. The available quota is 100\-perc%.
+By default the threshold is set to 5%.
+.SH SEE ALSO
+.IR inotify (7),
+.IR logrotate (8).
+.SH BUGS
+The heuristics used to clamp the file are faulty, if the disk is already filled to the threshold, the program assumes it's the log file's fault and truncates it.
+.br
+Slicing the file in half isn't necessarily the best approach. More disk usage statistics are needed to make an informed decision.
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..adafc3b
--- /dev/null
+++ b/main.c
@@ -0,0 +1,227 @@
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <sys/inotify.h>
+#include <sys/statvfs.h>
+#include "libutf/utf.h"
+#include "args.h"
+
+#define nil NULL
+
+typedef unsigned long long uvlong;
+
+enum
+{
+	Wlogfile,
+	Wlogdir,
+	NWATCH,
+
+	KB = 1024
+};
+
+char *argv0;
+int debug;
+
+void
+sysfatal(char *s)
+{
+	perror(s);
+	exit(1);
+}
+
+void
+dprint(char *fmt, ...)
+{
+	va_list ap;
+
+	if(!debug)
+		return;
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+}
+
+void*
+emalloc(ulong n)
+{
+	void *p;
+
+	p = malloc(n);
+	if(p == nil)
+		sysfatal("malloc");
+	return p;
+}
+
+char*
+estrdup(char *s)
+{
+	char *d;
+
+	d = strdup(s);
+	if(d == nil)
+		sysfatal("strdup");
+	return d;
+}
+
+void
+lockfile(int fd)
+{
+	if(flock(fd, LOCK_EX) < 0)
+		sysfatal("flock locking");
+}
+
+void
+unlockfile(int fd)
+{
+	if(flock(fd, LOCK_UN) < 0)
+		sysfatal("flock unlocking");
+}
+
+int
+checkusage(char *f, struct statvfs *vfs, int thres, ulong *flen)
+{
+	struct stat st;
+	uvlong total, free, barrier;
+
+	total = vfs->f_bsize*vfs->f_blocks;
+	free = vfs->f_bsize*vfs->f_bavail;
+	barrier = thres*total/100;
+	if(stat(f, &st) < 0)
+		sysfatal("stat");
+	*flen = st.st_size;
+	dprint("total %llu\nfree %llu\nbarrier %llu (%d%%)\nlogsize %llu\n",
+		total, free, barrier, thres, *flen);
+	if(free > barrier)
+		return 0;
+	return -1;
+}
+
+void
+defcon1(char *f, ulong flen)
+{
+	char tmpf[] = "/tmp/logwatch.XXXXXX";
+	char buf[128*KB];
+	int fd, tfd, n;
+
+	fd = open(f, O_RDWR);
+	if(fd < 0)
+		sysfatal("open");
+	tfd = mkstemp(tmpf);
+	if(tfd < 0)
+		sysfatal("mkstemp");
+	lockfile(fd);
+	if(lseek(fd, flen/2, SEEK_SET) < 0)
+		sysfatal("lseek [logfile]");
+	while((n = read(fd, buf, sizeof buf)) > 0)
+		if(write(tfd, buf, n) != n)
+			sysfatal("write [tmpfile]");
+	if(n < 0)
+		sysfatal("read [logfile]");
+	if(ftruncate(fd, 0) < 0)
+		sysfatal("ftruncate");
+	if(lseek(fd, 0, SEEK_SET) < 0)
+		sysfatal("lseek [logfile]");
+	if(lseek(tfd, 0, SEEK_SET) < 0)
+		sysfatal("lseek [tmpfile]");
+	while((n = read(tfd, buf, sizeof buf)) > 0)
+		if(write(fd, buf, n) != n)
+			sysfatal("write [logfile]");
+	if(n < 0)
+		sysfatal("read [tmpfile]");
+	unlockfile(fd);
+	close(tfd);
+	close(fd);
+	unlink(tmpf);
+}
+
+void
+usage(void)
+{
+	fprintf(stderr, "usage: %s [-d] [-t perc] logfile\n", argv0);
+	exit(1);
+}
+
+int
+main(int argc, char *argv[])
+{
+	struct inotify_event *e;
+	struct statvfs vfs;
+	char buf[sizeof(struct inotify_event)+NAME_MAX+1], *logfile, *logdir, *p;
+	int fd, watches[NWATCH], n, elen;
+	int thres;
+	ulong cookie, logfilelen;
+
+	thres = 5;
+	ARGBEGIN{
+	case 'd': debug++; break;
+	case 't':
+		thres = strtol(EARGF(usage()), nil, 10);
+		break;
+	default: usage();
+	}ARGEND;
+	if(argc != 1)
+		usage();
+	if(thres < 0 || thres > 100)
+		thres = 5;
+	p = strrchr(argv[0], '/');
+	if(p == nil)
+		logdir = getcwd(nil, 0);
+	else{
+		logdir = emalloc(p-argv[0]+1);
+		strncpy(logdir, argv[0], p-argv[0]);
+		logdir[p-argv[0]] = 0;
+	}
+	logfile = estrdup(p? p+1: argv[0]);
+	fd = inotify_init();
+	if(fd < 0)
+		sysfatal("inotify_init");
+	watches[Wlogfile] = inotify_add_watch(fd, logfile, IN_MODIFY);
+	if(watches[Wlogfile] < 0)
+		sysfatal("inotify_add_watch [file]");
+	watches[Wlogdir] = inotify_add_watch(fd, logdir, IN_MOVE);
+	if(watches[Wlogdir] < 0)
+		sysfatal("inotify_add_watch [dir]");
+	dprint("file: %d\ndir: %d\n", watches[Wlogfile], watches[Wlogdir]);
+	cookie = 0;
+	while((n = read(fd, buf, sizeof buf)) >= 0){
+Decode:
+		e = (struct inotify_event*)buf;
+		if(e->wd == watches[Wlogfile]){
+			if((e->mask & IN_MODIFY) != 0)
+				dprint("modified %s\n", logfile);
+			if((e->mask & IN_IGNORED) != 0){
+				dprint("deleted %s\n", logfile);
+				exit(0);
+			}
+			if(statvfs(logdir, &vfs) < 0)
+				sysfatal("statvfs");
+			if(checkusage(logfile, &vfs, thres, &logfilelen) < 0)
+				defcon1(logfile, logfilelen);
+		}else if(e->wd == watches[Wlogdir]){
+			if((e->mask & IN_MOVED_FROM) != 0)
+				if(e->len > 0 && strcmp(e->name, logfile) == 0)
+					cookie = e->cookie;
+			if((e->mask & IN_MOVED_TO) != 0)
+				if(e->cookie == cookie && e->len > 0){
+					dprint("rename from %s", logfile);
+					free(logfile);
+					logfile = estrdup(e->name);
+					dprint(" to %s\n", logfile);
+				}
+		}
+		elen = sizeof(struct inotify_event)+e->len;
+		if(n > elen){
+			p = buf+elen;
+			memmove(buf, p, n-elen);
+			n -= elen;
+			goto Decode;
+		}
+	}
+	exit(0);
+}
diff --git a/readme.md b/readme.md
new file mode 100644
index 0000000..c41cc49
--- /dev/null
+++ b/readme.md
@@ -0,0 +1,3 @@
+# logwatch(8)
+
+It requires libutf from https://9fans.github.io/plan9port/unix/.