Change the behaviour of -F slightly; it now persists (forever) in

trying to open files rather than giving up when it encounters an
error.  ENOENT errors are not reported.

As a result, files that are moved away then recreated are not at
risk of being 'lost' to tail.  Files that are recreated and
temporarily have unreadable permissions will be shown when they
are fixed.

This behaviour is consistent with the GNU version of tail but
without the verbiage that goes with the GNU version.

This change also fixes error messages accompanying -f and -F.
They no longer report problems with (null)!

MFC after:	3 weeks

1 files changed, 89 insertions, 61 deletions

diff --git a/usr.bin/tail/forward.c b/usr.bin/tail/forward.c
index c79c4382de04..6dab72ed0087 100644
--- a/usr.bin/tail/forward.c
+++ b/usr.bin/tail/forward.c
@@ -61,8 +61,8 @@ static const char sccsid[] = "@(#)forward.c	8.1 (Berkeley) 6/6/93";
 
 #include "extern.h"
 
-static void rlines(FILE *, off_t, struct stat *);
-static void show(file_info_t *);
+static void rlines(FILE *, const char *fn, off_t, struct stat *);
+static int show(file_info_t *);
 static void set_events(file_info_t *files);
 
 /* defines for inner loop actions */
@@ -99,7 +99,7 @@ static const file_info_t *last;
  *	NOREG	cyclically read lines into a wrap-around array of buffers
  */
 void
-forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
+forward(FILE *fp, const char *fn, enum STYLE style, off_t off, struct stat *sbp)
 {
 	int ch;
 
@@ -111,13 +111,13 @@ forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 			if (sbp->st_size < off)
 				off = sbp->st_size;
 			if (fseeko(fp, off, SEEK_SET) == -1) {
-				ierr();
+				ierr(fn);
 				return;
 			}
 		} else while (off--)
 			if ((ch = getc(fp)) == EOF) {
 				if (ferror(fp)) {
-					ierr();
+					ierr(fn);
 					return;
 				}
 				break;
@@ -129,7 +129,7 @@ forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 		for (;;) {
 			if ((ch = getc(fp)) == EOF) {
 				if (ferror(fp)) {
-					ierr();
+					ierr(fn);
 					return;
 				}
 				break;
@@ -142,36 +142,36 @@ forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 		if (S_ISREG(sbp->st_mode)) {
 			if (sbp->st_size >= off &&
 			    fseeko(fp, -off, SEEK_END) == -1) {
-				ierr();
+				ierr(fn);
 				return;
 			}
 		} else if (off == 0) {
 			while (getc(fp) != EOF);
 			if (ferror(fp)) {
-				ierr();
+				ierr(fn);
 				return;
 			}
 		} else
-			if (bytes(fp, off))
+			if (bytes(fp, fn, off))
 				return;
 		break;
 	case RLINES:
 		if (S_ISREG(sbp->st_mode))
 			if (!off) {
 				if (fseeko(fp, (off_t)0, SEEK_END) == -1) {
-					ierr();
+					ierr(fn);
 					return;
 				}
 			} else
-				rlines(fp, off, sbp);
+				rlines(fp, fn, off, sbp);
 		else if (off == 0) {
 			while (getc(fp) != EOF);
 			if (ferror(fp)) {
-				ierr();
+				ierr(fn);
 				return;
 			}
 		} else
-			if (lines(fp, off))
+			if (lines(fp, fn, off))
 				return;
 		break;
 	default:
@@ -182,7 +182,7 @@ forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
 		if (putchar(ch) == EOF)
 			oerr();
 	if (ferror(fp)) {
-		ierr();
+		ierr(fn);
 		return;
 	}
 	(void)fflush(stdout);
@@ -192,10 +192,7 @@ forward(FILE *fp, enum STYLE style, off_t off, struct stat *sbp)
  * rlines -- display the last offset lines of the file.
  */
 static void
-rlines(fp, off, sbp)
-	FILE *fp;
-	off_t off;
-	struct stat *sbp;
+rlines(FILE *fp, const char *fn, off_t off, struct stat *sbp)
 {
 	struct mapinfo map;
 	off_t curoff, size;
@@ -214,7 +211,7 @@ rlines(fp, off, sbp)
 	curoff = size - 2;
 	while (curoff >= 0) {
 		if (curoff < map.mapoff && maparound(&map, curoff) != 0) {
-			ierr();
+			ierr(fn);
 			return;
 		}
 		for (i = curoff - map.mapoff; i >= 0; i--)
@@ -227,41 +224,44 @@ rlines(fp, off, sbp)
 	}
 	curoff++;
 	if (mapprint(&map, curoff, size - curoff) != 0) {
-		ierr();
+		ierr(fn);
 		exit(1);
 	}
 
 	/* Set the file pointer to reflect the length displayed. */
 	if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) {
-		ierr();
+		ierr(fn);
 		return;
 	}
 	if (map.start != NULL && munmap(map.start, map.maplen)) {
-		ierr();
+		ierr(fn);
 		return;
 	}
 }
 
-static void
+static int
 show(file_info_t *file)
 {
-    int ch;
+	int ch;
 
-    while ((ch = getc(file->fp)) != EOF) {
-	if (last != file && no_files > 1) {
-		if (!qflag)
-			(void)printf("\n==> %s <==\n", file->file_name);
-		last = file;
+	while ((ch = getc(file->fp)) != EOF) {
+		if (last != file && no_files > 1) {
+			if (!qflag)
+				(void)printf("\n==> %s <==\n", file->file_name);
+			last = file;
+		}
+		if (putchar(ch) == EOF)
+			oerr();
+	}
+	(void)fflush(stdout);
+	if (ferror(file->fp)) {
+		fclose(file->fp);
+		file->fp = NULL;
+		ierr(file->file_name);
+		return 0;
 	}
-	if (putchar(ch) == EOF)
-		oerr();
-    }
-    (void)fflush(stdout);
-    if (ferror(file->fp)) {
-	    file->fp = NULL;
-	    ierr();
-    } else
-	    clearerr(file->fp);
+	clearerr(file->fp);
+	return 1;
 }
 
 static void
@@ -309,7 +309,7 @@ set_events(file_info_t *files)
 void
 follow(file_info_t *files, enum STYLE style, off_t off)
 {
-	int active, i, n = -1;
+	int active, ev_change, i, n = -1;
 	struct stat sb2;
 	file_info_t *file;
 	struct timespec ts;
@@ -325,12 +325,12 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 			n++;
 			if (no_files > 1 && !qflag)
 				(void)printf("\n==> %s <==\n", file->file_name);
-			forward(file->fp, style, off, &file->st);
+			forward(file->fp, file->file_name, style, off, &file->st);
 			if (Fflag && fileno(file->fp) != STDIN_FILENO)
-			    n++;
+				n++;
 		}
 	}
-	if (! active)
+	if (!Fflag && !active)
 		return;
 
 	last = --file;
@@ -344,28 +344,56 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 	set_events(files);
 
 	for (;;) {
-		for (i = 0, file = files; i < no_files; i++, file++) {
-			if (! file->fp)
-				continue;
-			if (Fflag && file->fp && fileno(file->fp) != STDIN_FILENO) {
-				if (stat(file->file_name, &sb2) == 0 &&
-				    (sb2.st_ino != file->st.st_ino ||
-				     sb2.st_dev != file->st.st_dev ||
-				     sb2.st_nlink == 0)) {
-					show(file);
-					file->fp = freopen(file->file_name, "r", file->fp);
-					if (file->fp == NULL) {
-						ierr();
-						continue;
-					} else {
-						memcpy(&file->st, &sb2, sizeof(struct stat));
-						set_events(files);
+		ev_change = 0;
+		if (Fflag) {
+			for (i = 0, file = files; i < no_files; i++, file++) {
+				if (!file->fp) {
+					file->fp = fopen(file->file_name, "r");
+					if (file->fp != NULL &&
+					    fstat(fileno(file->fp), &file->st)
+					    == -1) {
+						fclose(file->fp);
+						file->fp = NULL;
 					}
+					if (file->fp != NULL)
+						ev_change++;
+					continue;
+				}
+				if (fileno(file->fp) == STDIN_FILENO)
+					continue;
+				if (stat(file->file_name, &sb2) == -1) {
+					if (errno != ENOENT)
+						ierr(file->file_name);
+					show(file);
+					fclose(file->fp);
+					file->fp = NULL;
+					ev_change++;
+					continue;
+				}
+
+				if (sb2.st_ino != file->st.st_ino ||
+				    sb2.st_dev != file->st.st_dev ||
+				    sb2.st_nlink == 0) {
+					show(file);
+					file->fp = freopen(file->file_name, "r",
+					    file->fp);
+					if (file->fp != NULL)
+						memcpy(&file->st, &sb2,
+						    sizeof(struct stat));
+					else if (errno != ENOENT)
+						ierr(file->file_name);
+					ev_change++;
 				}
 			}
-			show(file);
 		}
 
+		for (i = 0, file = files; i < no_files; i++, file++)
+			if (file->fp && !show(file))
+				ev_change++;
+
+		if (ev_change)
+			set_events(files);
+
 		switch (action) {
 		case USE_KQUEUE:
 			ts.tv_sec = 1;
@@ -381,9 +409,9 @@ follow(file_info_t *files, enum STYLE style, off_t off)
 				/* timeout */
 				break;
 			} else if (ev->filter == EVFILT_READ && ev->data < 0) {
-				 /* file shrank, reposition to end */
+				/* file shrank, reposition to end */
 				if (lseek(ev->ident, (off_t)0, SEEK_END) == -1) {
-					ierr();
+					ierr(file->file_name);
 					continue;
 				}
 			}