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Diffstat (limited to 'usr.bin/tail/forward.c')
| -rw-r--r-- | usr.bin/tail/forward.c | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/usr.bin/tail/forward.c b/usr.bin/tail/forward.c new file mode 100644 index 0000000..8e32cc4 --- /dev/null +++ b/usr.bin/tail/forward.c @@ -0,0 +1,234 @@ +/*- + * 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 +static char sccsid[] = "@(#)forward.c 8.1 (Berkeley) 6/6/93"; +#endif /* not lint */ + +#include <sys/types.h> +#include <sys/stat.h> +#include <sys/time.h> +#include <sys/mman.h> + +#include <limits.h> +#include <fcntl.h> +#include <errno.h> +#include <unistd.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include "extern.h" + +static void 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; +{ + register int ch; + struct timeval second; + fd_set zero; + + 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 + bytes(fp, off); + 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 + lines(fp, off); + break; + } + + /* + * We pause for one second after displaying any data that has + * accumulated since we read the file. + */ + if (fflag) { + FD_ZERO(&zero); + second.tv_sec = 1; + second.tv_usec = 0; + } + + for (;;) { + while ((ch = getc(fp)) != EOF) + if (putchar(ch) == EOF) + oerr(); + if (ferror(fp)) { + ierr(); + return; + } + (void)fflush(stdout); + if (!fflag) + break; + /* Sleep(3) is eight system calls. Do it fast. */ + if (select(0, &zero, &zero, &zero, &second) == -1) + err(1, "select: %s", strerror(errno)); + clearerr(fp); + } +} + +/* + * rlines -- display the last offset lines of the file. + */ +static void +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; + + if (size > SIZE_T_MAX) { + err(0, "%s: %s", fname, strerror(EFBIG)); + return; + } + + if ((start = mmap(NULL, (size_t)size, + PROT_READ, 0, fileno(fp), (off_t)0)) == (caddr_t)-1) { + err(0, "%s: %s", fname, strerror(EFBIG)); + return; + } + + /* 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; + } + if (munmap(start, (size_t)sbp->st_size)) { + err(0, "%s: %s", fname, strerror(errno)); + return; + } +} |
