/*- * Copyright (c) 1991, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software contributed to Berkeley by * Edward Sze-Tyan Wang. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #ifndef lint #if 0 static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; #endif static const char rcsid[] = "$FreeBSD: head/usr.bin/tail/forward.c 77823 2001-06-06 17:47:13Z jlemon $"; #endif /* not lint */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include "extern.h" static void rlines __P((FILE *, long, struct stat *)); /* defines for inner loop actions */ #define USE_SLEEP 0 #define USE_KQUEUE 1 #define ADD_EVENTS 2 /* * forward -- display the file, from an offset, forward. * * There are eight separate cases for this -- regular and non-regular * files, by bytes or lines and from the beginning or end of the file. * * FBYTES byte offset from the beginning of the file * REG seek * NOREG read, counting bytes * * FLINES line offset from the beginning of the file * REG read, counting lines * NOREG read, counting lines * * RBYTES byte offset from the end of the file * REG seek * NOREG cyclically read characters into a wrap-around buffer * * RLINES * REG mmap the file and step back until reach the correct offset. * NOREG cyclically read lines into a wrap-around array of buffers */ void forward(fp, style, off, sbp) FILE *fp; enum STYLE style; long off; struct stat *sbp; { int ch, kq = -1; int action = USE_SLEEP; struct kevent ev[2]; struct stat sb2; switch(style) { case FBYTES: if (off == 0) break; if (S_ISREG(sbp->st_mode)) { if (sbp->st_size < off) off = sbp->st_size; if (fseek(fp, off, SEEK_SET) == -1) { ierr(); return; } } else while (off--) if ((ch = getc(fp)) == EOF) { if (ferror(fp)) { ierr(); return; } break; } break; case FLINES: if (off == 0) break; for (;;) { if ((ch = getc(fp)) == EOF) { if (ferror(fp)) { ierr(); return; } break; } if (ch == '\n' && !--off) break; } break; case RBYTES: if (S_ISREG(sbp->st_mode)) { if (sbp->st_size >= off && fseek(fp, -off, SEEK_END) == -1) { ierr(); return; } } else if (off == 0) { while (getc(fp) != EOF); if (ferror(fp)) { ierr(); return; } } else if (bytes(fp, off)) return; break; case RLINES: if (S_ISREG(sbp->st_mode)) if (!off) { if (fseek(fp, 0L, SEEK_END) == -1) { ierr(); return; } } else rlines(fp, off, sbp); else if (off == 0) { while (getc(fp) != EOF); if (ferror(fp)) { ierr(); return; } } else if (lines(fp, off)) return; break; } if (fflag) { kq = kqueue(); if (kq < 0) err(1, "kqueue"); action = ADD_EVENTS; } for (;;) { while ((ch = getc(fp)) != EOF) if (putchar(ch) == EOF) oerr(); if (ferror(fp)) { ierr(); return; } (void)fflush(stdout); if (! fflag) break; clearerr(fp); switch (action) { case ADD_EVENTS: { int n = 0; struct timespec ts = { 0, 0 }; if (Fflag && fileno(fp) != STDIN_FILENO) { EV_SET(&ev[n], fileno(fp), EVFILT_VNODE, EV_ADD | EV_ENABLE | EV_CLEAR, NOTE_DELETE | NOTE_RENAME, 0, 0); n++; } EV_SET(&ev[n], fileno(fp), EVFILT_READ, EV_ADD | EV_ENABLE | EV_CLEAR, 0, 0, 0); n++; if (kevent(kq, ev, n, NULL, 0, &ts) < 0) { close(kq); kq = -1; action = USE_SLEEP; } else { action = USE_KQUEUE; } break; } case USE_KQUEUE: if (kevent(kq, NULL, 0, ev, 1, NULL) < 0) err(1, "kevent"); if (ev->filter == EVFILT_VNODE) { /* file was rotated, wait until it reappears */ action = USE_SLEEP; } else if (ev->data < 0) { /* file shrank, reposition to end */ if (fseek(fp, 0L, SEEK_END) == -1) { ierr(); return; } } break; case USE_SLEEP: (void) usleep(250000); clearerr(fp); if (Fflag && fileno(fp) != STDIN_FILENO && stat(fname, &sb2) != -1) { if (sb2.st_ino != sbp->st_ino || sb2.st_dev != sbp->st_dev || sb2.st_rdev != sbp->st_rdev || sb2.st_nlink == 0) { fp = freopen(fname, "r", fp); if (fp == NULL) { ierr(); break; } *sbp = sb2; if (kq != -1) action = ADD_EVENTS; } else if (kq != -1) { action = USE_KQUEUE; } } break; } } } /* * rlines -- display the last offset lines of the file. */ static void rlines(fp, off, sbp) FILE *fp; long off; struct stat *sbp; { struct mapinfo map; off_t curoff, size; int i; if (!(size = sbp->st_size)) return; map.start = NULL; map.fd = fileno(fp); map.mapoff = map.maxoff = size; /* * Last char is special, ignore whether newline or not. Note that * size == 0 is dealt with above, and size == 1 sets curoff to -1. */ curoff = size - 2; while (curoff >= 0) { if (curoff < map.mapoff && maparound(&map, curoff) != 0) { ierr(); return; } for (i = curoff - map.mapoff; i >= 0; i--) if (map.start[i] == '\n' && --off == 0) break; /* `i' is either the map offset of a '\n', or -1. */ curoff = map.mapoff + i; if (i >= 0) break; } curoff++; if (mapprint(&map, curoff, size - curoff) != 0) { ierr(); exit(1); } /* Set the file pointer to reflect the length displayed. */ if (fseeko(fp, sbp->st_size, SEEK_SET) == -1) { ierr(); return; } if (map.start != NULL && munmap(map.start, map.maplen)) { ierr(); return; } }