/* $OpenBSD: forward.c,v 1.12 2001/08/18 14:49:15 art Exp $ */ /* $NetBSD: forward.c,v 1.7 1996/02/13 16:49:10 ghudson Exp $ */ /*- * 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 char rcsid[] = "$OpenBSD: forward.c,v 1.12 2001/08/18 14:49:15 art Exp $"; #endif /* not lint */ #include #include #include #include #include #include #include #include #include #include #include #include #include "extern.h" static int rlines __P((FILE *, long, struct stat *)); /* * 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; struct stat nsb; int kq; struct kevent ke; 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 if (rlines(fp, off, sbp) != 0) lines(fp, off); } else if (off == 0) { while (getc(fp) != EOF) ; if (ferror(fp)) { ierr(); return; } } else { if (lines(fp, off)) return; } break; } kq = -1; kq_retry: if (fflag && ((kq = kqueue()) >= 0)) { ke.ident = fileno(fp); ke.flags = EV_ENABLE|EV_ADD|EV_CLEAR; ke.filter = EVFILT_READ; ke.fflags = ke.data = 0; ke.udata = NULL; if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0) { close(kq); kq = -1; } else if (S_ISREG(sbp->st_mode)) { ke.ident = fileno(fp); ke.flags = EV_ENABLE|EV_ADD|EV_CLEAR; ke.filter = EVFILT_VNODE; ke.fflags = NOTE_DELETE | NOTE_RENAME; if (kevent(kq, &ke, 1, NULL, 0, NULL) < 0) { close(kq); kq = -1; } } } for (;;) { while (!feof(fp) && (ch = getc(fp)) != EOF) if (putchar(ch) == EOF) oerr(); if (ferror(fp)) { ierr(); if (kq != -1) close(kq); return; } (void)fflush(stdout); if (!fflag) break; clearerr(fp); if (kq < 0 || kevent(kq, NULL, 0, &ke, 1, NULL) <= 0) { sleep(1); } else if (ke.filter == EVFILT_READ) { continue; } else { /* * 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; } 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; } (void)memcpy(sbp, &nsb, sizeof(nsb)); goto kq_retry; } else if (nsb.st_size < sbp->st_size) { warnx("%s has been truncated, resetting.", fname); rewind(fp); (void)memcpy(sbp, &nsb, sizeof(nsb)); } } if (kq >= 0) close(kq); } /* * rlines -- display the last offset lines of the file. */ static int rlines(fp, off, sbp) FILE *fp; long off; struct stat *sbp; { register off_t size; register char *p; char *start; if (!(size = sbp->st_size)) return (0); if (size > SIZE_T_MAX) return (1); if ((start = mmap(NULL, (size_t)size, PROT_READ, MAP_PRIVATE, fileno(fp), (off_t)0)) == MAP_FAILED) return (1); /* Last char is special, ignore whether newline or not. */ for (p = start + size - 1; --size;) if (*--p == '\n' && !--off) { ++p; break; } /* Set the file pointer to reflect the length displayed. */ size = sbp->st_size - size; WR(p, size); if (fseek(fp, (long)sbp->st_size, SEEK_SET) == -1) { ierr(); return (1); } if (munmap(start, (size_t)sbp->st_size)) { ierr(); return (1); } return (0); }