Permit tail -f to follow multiple files, useful when you want to monitor

several logfiles in a single terminal. split forward() and move the
corresponding -rewritten- code to follow().
Closes PR 5092.

ok millert@ gilles@ sobrado@

3 files changed, 189 insertions, 83 deletions

diff --git a/usr.bin/tail/extern.h b/usr.bin/tail/extern.h
index 5ab91243f51..1cda5b85cfd 100644
--- a/usr.bin/tail/extern.h
+++ b/usr.bin/tail/extern.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: extern.h,v 1.9 2004/02/16 19:48:21 otto Exp $	*/
+/*	$OpenBSD: extern.h,v 1.10 2008/10/17 11:38:20 landry Exp $	*/
 /*	$NetBSD: extern.h,v 1.3 1994/11/23 07:42:00 jtc Exp $	*/
 
 /*-
@@ -40,6 +40,7 @@ enum STYLE { NOTSET = 0, FBYTES, FLINES, RBYTES, RLINES, REVERSE };
 
 void forward(FILE *, enum STYLE, off_t, struct stat *);
 void reverse(FILE *, enum STYLE, off_t, struct stat *);
+void follow(char **, int, enum STYLE, off_t);
 
 int bytes(FILE *, off_t);
 int lines(FILE *, off_t);
diff --git a/usr.bin/tail/forward.c b/usr.bin/tail/forward.c
index 40e5f324058..e36498d9285 100644
--- a/usr.bin/tail/forward.c
+++ b/usr.bin/tail/forward.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: forward.c,v 1.23 2007/10/22 01:14:26 deraadt Exp $	*/
+/*	$OpenBSD: forward.c,v 1.24 2008/10/17 11:38:20 landry Exp $	*/
 /*	$NetBSD: forward.c,v 1.7 1996/02/13 16:49:10 ghudson Exp $	*/
 
 /*-
@@ -37,7 +37,7 @@
 #if 0
 static char sccsid[] = "@(#)forward.c	8.1 (Berkeley) 6/6/93";
 #endif
-static char rcsid[] = "$OpenBSD: forward.c,v 1.23 2007/10/22 01:14:26 deraadt Exp $";
+static char rcsid[] = "$OpenBSD: forward.c,v 1.24 2008/10/17 11:38:20 landry Exp $";
 #endif /* not lint */
 
 #include <sys/types.h>
@@ -48,6 +48,7 @@ static char rcsid[] = "$OpenBSD: forward.c,v 1.23 2007/10/22 01:14:26 deraadt Ex
 #include <stdio.h>
 #include <string.h>
 #include <unistd.h>
+#include <stdlib.h>
 
 #include "extern.h"
 
@@ -79,9 +80,6 @@ void
 forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 {
 	int ch;
-	struct stat nsb;
-	int kq, queue;
-	struct kevent ke;
 
 	switch(style) {
 	case FBYTES:
@@ -160,83 +158,188 @@ forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 		break;
 	}
 
+	while (!feof(fp) && (ch = getc(fp)) != EOF)
+		if (putchar(ch) == EOF)
+			oerr();
+	if (ferror(fp)) {
+		ierr();
+		return;
+	}
+	(void)fflush(stdout);
+}
+
+struct file_info {
+	FILE *fp;
+	char *fname;
+	struct stat fst;
+};
+
+/*
+ * follow one or multiple files, i.e don't stop when end-of-file is reached,
+ * but rather wait for additional data to be appended to the input.
+ * this implements -f switch.
+ */
+void
+follow(char **fnames, int nbfiles, enum STYLE style, off_t off)
+{
+	int ch, first, i;
+	int kq;
+	struct kevent ke;
+	struct stat cst;
+	FILE *fp;
+	struct file_info *files;
+
 	kq = -1;
-kq_retry:
-	if (fflag && ((kq = kqueue()) >= 0)) {
+	if ((kq = kqueue()) < 0)
+		err(2, "kqueue() failed");
+
+	if ((files = calloc(nbfiles, sizeof(struct file_info))) == NULL)
+		err(1, "calloc() failed");
+
+	for (first = 1, i = 0; (files[i].fname = *fnames++); i++) {
+		if ((fp = fopen(files[i].fname, "r")) == NULL ||
+		    fstat(fileno(fp), &(files[i].fst))) {
+			warn("%s",files[i].fname);
+			nbfiles--;
+			i--;
+			continue;
+		}
+		if (S_ISDIR(files[i].fst.st_mode)) {
+			warnx("%s is a directory, skipping.",files[i].fname);
+			nbfiles--;
+			i--;
+			continue;
+		}
+		files[i].fp = fp;
+		if (nbfiles > 1) {
+			(void)printf("%s==> %s <==\n",
+			    first ? "" : "\n", files[i].fname);
+			first = 0;
+		}
+
+		/* print from the given offset to the end */
+		if (off != 0) {
+			if (style == RBYTES) {
+				if (S_ISREG(files[i].fst.st_mode)) {
+					if (files[i].fst.st_size >= off &&
+					    fseeko(fp, -off, SEEK_END) == -1) {
+						ierr();
+						goto cleanup;
+					}
+				}
+				if (bytes(fp, off))
+					goto cleanup;
+			} else if (rlines(fp, off, &(files[i].fst)) != 0)
+				lines(fp, off);
+		}
+		(void)fflush(stdout);
+
+		/* one event to see if there is data to read */
+		ke.ident = fileno(fp);
 		EV_SET(&ke, fileno(fp), EVFILT_READ,
 		    EV_ENABLE | EV_ADD | EV_CLEAR,
-		    0,
-		    0, NULL);
-		if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0) {
-			close(kq);
-			kq = -1;
-		} else if (S_ISREG(sbp->st_mode)) {
+		    NULL, 0, NULL);
+		if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0)
+			goto cleanup;
+		else if (S_ISREG(files[i].fst.st_mode)) {
+			/* one event to detect if inode changed */
 			EV_SET(&ke, fileno(fp), EVFILT_VNODE,
 			    EV_ENABLE | EV_ADD | EV_CLEAR,
 			    NOTE_DELETE | NOTE_RENAME | NOTE_TRUNCATE,
 			    0, NULL);
-			if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0) {
-				close(kq);
-				kq = -1;
-			}
+			if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0)
+				goto cleanup;
 		}
 	}
 
+	/* no files to read */
+	if (nbfiles == 0)
+		goto cleanup;
+
+	if (fp == NULL)
+		fp = files[nbfiles - 1].fp;
+
 	for (;;) {
 		while (!feof(fp) && (ch = getc(fp)) != EOF)
 			if (putchar(ch) == EOF)
 				oerr();
-		if (ferror(fp)) {
-			ierr();
-			if (kq != -1)
-				close(kq);
-			return;
-		}
+		if (ferror(fp))
+			goto cleanup;
+
 		(void)fflush(stdout);
-		if (!fflag)
-			break;
 		clearerr(fp);
-		queue = 1;
-		if (kq < 0 || kevent(kq, NULL, 0, &ke, 1, NULL) <= 0) {
-			queue = 0;
+		/* give it a chance to fail.. */
+		if (kevent(kq, NULL, 0, &ke, 1, NULL) <= 0) {
 			sleep(1);
-		} else if (ke.filter == EVFILT_READ) {
 			continue;
-		} else if ((ke.fflags & NOTE_TRUNCATE) == 0) {
-			/*
-			 * File was renamed or deleted.
-			 *
-			 * Continue to look at it until a new file reappears
-			 * with the same name. 
-			 * Fall back to the old algorithm for that.
-			 */
-			close(kq);
-			kq = -1;
-		}
+		} else {
+			/* an event occured on file #i */
+			for (i = 0 ; i < nbfiles ; i++)
+				if (fileno(files[i].fp) == ke.ident)
+					break;
 
-		if (is_stdin || stat(fname, &nsb) != 0)
-			continue;
-		/* Reopen file if the inode changes or file was truncated */
-		if (nsb.st_ino != sbp->st_ino) {
-			warnx("%s has been replaced, reopening.", fname);
-			if ((fp = freopen(fname, "r", fp)) == NULL) {
-				ierr();
-				if (kq >= 0)
-					close(kq);
-				return;
+			/* EVFILT_READ event, check that it's on the current fp */
+			if (ke.filter == EVFILT_READ) {
+				if (fp != files[i].fp) {
+					(void)printf("\n==> %s <==\n",files[i].fname);
+					fp = files[i].fp;
+					clearerr(fp);
+				}
+			/* EVFILT_VNODE event and File was renamed or deleted */
+			} else if (ke.fflags & (NOTE_DELETE | NOTE_RENAME)) {
+				/* file didn't reappear */
+				if (stat(files[i].fname, &cst) != 0) {
+					warnx("%s has been renamed or deleted.", files[i].fname);
+					if (--nbfiles == 0)
+						goto cleanup;
+					/* overwrite with the latest file_info */
+					fp = files[nbfiles].fp;
+					(void)memcpy(&files[i], &files[nbfiles], sizeof(struct file_info));
+				} else {
+					/* Reopen file if the inode changed */
+					if (cst.st_ino != files[i].fst.st_ino) {
+						warnx("%s has been replaced, reopening.", files[i].fname);
+						if ((fp = freopen(files[i].fname, "r", files[i].fp)) == NULL) {
+							ierr();
+							goto cleanup;
+						}
+						/*
+						 * on freopen(), events corresponding to the fp
+						 * were deleted from kqueue, we readd them
+						*/
+						ke.ident = fileno(fp);
+						EV_SET(&ke, fileno(fp), EVFILT_READ,
+						    EV_ENABLE | EV_ADD | EV_CLEAR,
+						    NULL, 0, NULL);
+						if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0)
+							goto cleanup;
+						else if (S_ISREG(files[i].fst.st_mode)) {
+							EV_SET(&ke, fileno(fp), EVFILT_VNODE,
+							    EV_ENABLE | EV_ADD | EV_CLEAR,
+							    NOTE_DELETE | NOTE_RENAME | NOTE_TRUNCATE,
+							    0, NULL);
+							if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0)
+								goto cleanup;
+						}
+						files[i].fp = fp;
+					}
+					(void)memcpy(&(files[i].fst), &cst, sizeof(cst));
+				}
+			} else if (ke.fflags & NOTE_TRUNCATE) {
+				/* reset file if it was truncated */
+				warnx("%s has been truncated, resetting.", files[i].fname);
+				fpurge(files[i].fp);
+				rewind(files[i].fp);
+				continue;
 			}
-			(void)memcpy(sbp, &nsb, sizeof(nsb));
-			goto kq_retry;
-		} else if ((queue && (ke.fflags & NOTE_TRUNCATE)) ||
-		    (!queue && nsb.st_size < sbp->st_size)) {
-			warnx("%s has been truncated, resetting.", fname);
-			fpurge(fp);
-			rewind(fp);
 		}
-		(void)memcpy(sbp, &nsb, sizeof(nsb));
 	}
+
+cleanup:
 	if (kq >= 0)
 		close(kq);
+	free(files);
+	return;
 }
 
 /*
diff --git a/usr.bin/tail/tail.c b/usr.bin/tail/tail.c
index 2246e7b77db..10d164290cd 100644
--- a/usr.bin/tail/tail.c
+++ b/usr.bin/tail/tail.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tail.c,v 1.14 2007/10/31 16:29:50 jmc Exp $	*/
+/*	$OpenBSD: tail.c,v 1.15 2008/10/17 11:38:20 landry Exp $	*/
 
 /*-
  * Copyright (c) 1991, 1993
@@ -42,7 +42,7 @@ static char copyright[] =
 #if 0
 static char sccsid[] = "@(#)tail.c	8.1 (Berkeley) 6/6/93";
 #endif
-static char rcsid[] = "$OpenBSD: tail.c,v 1.14 2007/10/31 16:29:50 jmc Exp $";
+static char rcsid[] = "$OpenBSD: tail.c,v 1.15 2008/10/17 11:38:20 landry Exp $";
 #endif /* not lint */
 
 #include <sys/types.h>
@@ -132,10 +132,6 @@ main(int argc, char *argv[])
 		}
 	argc -= optind;
 	argv += optind;
-
-	if (fflag && argc > 1)
-		errx(1, "-f option only appropriate for a single file");
-
 	/*
 	 * If displaying in reverse, don't permit follow option, and convert
 	 * style values.
@@ -162,27 +158,33 @@ main(int argc, char *argv[])
 			style = RLINES;
 		}
 	}
+	
+	if (*argv) {
+		if (fflag) {
+			follow(argv, argc, style, off);
+		}
+		else {	
+			for (first = 1; (fname = *argv++);) {
+				if ((fp = fopen(fname, "r")) == NULL ||
+				    fstat(fileno(fp), &sb)) {
+					ierr();
+					continue;
+				}
+				if (argc > 1) {
+					(void)printf("%s==> %s <==\n",
+					    first ? "" : "\n", fname);
+					first = 0;
+					(void)fflush(stdout);
+				}
 
-	if (*argv)
-		for (first = 1; (fname = *argv++);) {
-			if ((fp = fopen(fname, "r")) == NULL ||
-			    fstat(fileno(fp), &sb)) {
-				ierr();
-				continue;
+				if (rflag)
+					reverse(fp, style, off, &sb);
+				else
+					forward(fp, style, off, &sb);
+				(void)fclose(fp);
 			}
-			if (argc > 1) {
-				(void)printf("%s==> %s <==\n",
-				    first ? "" : "\n", fname);
-				first = 0;
-				(void)fflush(stdout);
-			}
-
-			if (rflag)
-				reverse(fp, style, off, &sb);
-			else
-				forward(fp, style, off, &sb);
-			(void)fclose(fp);
 		}
+	}
 	else {
 		fname = "stdin";
 		is_stdin = 1;