clean up import, add rcsid's.
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cgd
parent
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@ -1,11 +1,13 @@
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# from: @(#)Makefile 5.14 (Berkeley) 6/25/90
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# $Id: Makefile,v 1.3 1993/10/23 01:13:35 jtc Exp $
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# USERMEM should be the amount of available user memory in bytes.
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# Set it to zero, for physical memory less than 1 Meg.
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USERMEM=4194304
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# from: @(#)Makefile 8.2 (Berkeley) 4/17/94
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# $Id: Makefile,v 1.4 1994/06/13 14:48:14 cgd Exp $
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PROG= compress
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CFLAGS+=-DBSD4_2 -DSACREDMEM=256000 -DUSERMEM=${USERMEM}
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SRCS= compress.c zopen.c
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LINKS= ${BINDIR}/compress ${BINDIR}/uncompress
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MLINKS= compress.1 uncompress.1 compress.1 zcat.1
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afterinstall:
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install -c -o ${BINOWN} -g ${BINGRP} -m ${BINMODE} \
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${.CURDIR}/zcat.sh ${DESTDIR}/usr/bin/zcat
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.include <bsd.prog.mk>
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@ -1,5 +1,5 @@
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.\" Copyright (c) 1986, 1990 The Regents of the University of California.
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.\" All rights reserved.
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.\" Copyright (c) 1986, 1990, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" James A. Woods, derived from original work by Spencer Thomas
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@ -33,10 +33,10 @@
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" from: @(#)compress.1 6.10 (Berkeley) 7/30/91
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.\" $Id: compress.1,v 1.2 1993/08/01 07:33:30 mycroft Exp $
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.\" from: @(#)compress.1 8.2 (Berkeley) 4/18/94
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.\" $Id: compress.1,v 1.3 1994/06/13 14:48:22 cgd Exp $
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.\"
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.Dd July 30, 1991
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.Dd April 18, 1994
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.Dt COMPRESS 1
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.Os BSD 4.3
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.Sh NAME
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@ -46,97 +46,93 @@
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.Nd compress and expand data
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.Sh SYNOPSIS
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.Nm compress
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.Op Fl f
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.Op Fl v
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.Op Fl c
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.Op Fl cfv
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.Op Fl b Ar bits
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.Op Ar
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.Nm uncompress
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.Op Fl f
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.Op Fl v
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.Op Fl c
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.Ar
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.Op Fl cfv
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.Op Ar
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.Nm zcat
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.Op Ar
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.Sh DESCRIPTION
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.Nm Compress
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reduces the size of the named files using adaptive Lempel-Ziv coding.
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Whenever possible,
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each
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Each
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.Ar file
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is replaced by one with the extension
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.Ar \&.Z ,
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while keeping the same ownership modes, access and modification times.
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If no files are specified, the standard input is compressed to the
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standard output.
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Compressed files can be restored to their original form using
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.Nm uncompress
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or
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.Nm zcat
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is renamed to the same name plus the extension
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.Dq .Z .
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As many of the modification time, access time, file flags, file mode,
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user ID, and group ID as allowed by permissions are retained in the
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new file.
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If compression would not reduce the size of a
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.Ar file ,
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the file is ignored.
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.Pp
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.Nm Uncompress
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restores the compressed files to their original form, renaming the
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files by deleting the
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.Dq .Z
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extension.
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.Pp
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.Nm Zcat
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is an alias for
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.Dq "uncompress -c" .
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.Pp
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If renaming the files would cause files to be overwritten and the standard
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input device is a terminal, the user is prompted (on the standard error
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output) for confirmation.
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If prompting is not possible or confirmation is not received, the files
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are not overwritten.
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.Pp
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If no files are specified, the standard input is compressed or uncompressed
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to the standard output.
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If either the input and output files are not regular files, the checks for
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reduction in size and file overwriting are not performed, the input file is
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not removed, and the attributes of the input file are not retained.
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.Pp
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The options are as follows:
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.Bl -tag -width Ds
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.It Fl b
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Specify the
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.Ar bits
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code limit (see below).
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.It Fl c
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Compressed or uncompressed output is written to the standard output.
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No files are modified.
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.It Fl f
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Force compression of
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.Ar file ,
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even if it does not actually shrink
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or the corresponding
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.Ar file.Z
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file already exists.
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Except when run in the background under
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.Pa /bin/sh ,
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if
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.Fl f
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is not given the user is prompted as to whether an existing
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.Ar file.Z
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file should be overwritten.
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.It Fl c
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(``cat'').
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.Nm Compress/uncompress
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writes to the standard output; no files are changed.
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The nondestructive behavior of
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.Nm zcat
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is identical to that of
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.Nm uncompress
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.Fl c .
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.It Fl b
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Specify
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.Ar bits
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code limit (see below).
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even if it is not actually reduced in size.
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Additionally, files are overwritten without prompting for confirmation.
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.It Fl v
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Print the percentage reduction of each file.
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.El
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.Pp
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.Nm Compress
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uses the modified Lempel-Ziv algorithm popularized in
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"A Technique for High Performance Data Compression",
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Terry A. Welch,
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.Em IEEE Computer ,
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vol. 17,
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.no 6
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(June 1984), pp. 8-19.
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uses a modified Lempel-Ziv algorithm.
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Common substrings in the file are first replaced by 9-bit codes 257 and up.
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When code 512 is reached, the algorithm switches to 10-bit codes and
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continues to use more bits until the
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limit specified by the
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.Fl b
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flag is reached (default 16).
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flag is reached (the default is 16).
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.Ar Bits
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must be between 9 and 16. The default can be changed in the source to allow
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.Nm compress
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to be run on a smaller machine.
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must be between 9 and 16.
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.Pp
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After the
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.Ar bits
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limit is attained,
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limit is reached,
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.Nm compress
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periodically checks the compression ratio. If it is increasing,
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periodically checks the compression ratio.
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If it is increasing,
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.Nm compress
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continues to use the existing code dictionary. However,
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if the compression ratio decreases,
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continues to use the existing code dictionary.
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However, if the compression ratio decreases,
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.Nm compress
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discards the table of substrings and rebuilds it from scratch. This allows
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the algorithm to adapt to the next "block" of the file.
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.Pp
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Note that the
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The
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.Fl b
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flag is omitted for
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.Ar uncompress
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@ -152,90 +148,24 @@ The amount of compression obtained depends on the size of the
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input, the number of
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.Ar bits
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per code, and the distribution of common substrings.
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Typically, text such as source code or English
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is reduced by 50\-60%.
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Compression is generally much better than that achieved by
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Huffman coding (as used in the historical command
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pack),
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or adaptive Huffman coding (as
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used in the historical command
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compact),
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and takes less time to compute.
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Typically, text such as source code or English is reduced by 50\-60%.
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Compression is generally much better than that achieved by Huffman
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coding (as used in the historical command pack), or adaptive Huffman
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coding (as used in the historical command compact), and takes less
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time to compute.
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.Pp
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If an error occurs, exit status is 1;
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if the last file was not compressed because it became larger, the status
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is 2; otherwise the status is 0.
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.Sh DIAGNOSTICS
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.Bl -tag -width flag
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.It "Usage: compress [-fvc] [-b maxbits] [file ...]"
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Invalid options were specified on the command line.
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.It "Missing maxbits"
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Maxbits must follow
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.Fl b .
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.It Ar file : No "not in compressed format"
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The file specified to
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.Ar uncompress
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has not been compressed.
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.It Xo
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.Ar file : No "compressed with"
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.Ar \&xx No "bits, can only handle"
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.Ar \&yy No bits
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.Xc
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.Ar File
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was compressed by a program that could deal with
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more
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.Ar bits
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than the compress code on this machine.
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Recompress the file with smaller
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.Ar bits .
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.It Ar file : No "already has .Z suffix -- no change"
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The file is assumed to be already compressed.
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Rename the file and try again.
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.It Ar file : No "filename too long to tack on .Z"
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The file cannot be compressed because its name is longer than
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12 characters.
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Rename and try again.
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This message does not occur on
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.Bx
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systems.
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.It Ar file No "already exists; do you wish to overwrite (y or n)?"
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Respond "y" if you want the output file to be replaced; "n" if not.
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.It "uncompress: corrupt input"
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A
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.Dv SIGSEGV
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violation was detected which usually means that the input file is
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corrupted.
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.It Compression: Em "xx.xx%"
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Percentage of the input saved by compression.
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(Relevant only for
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.Fl v . )
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.It "-- not a regular file: unchanged"
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When the input file is not a regular file,
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(e.g. a directory), it is
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left unaltered.
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.It "-- has" Ar xx No "other links: unchanged"
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The input file has links; it is left unchanged. See
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.Xr ln 1
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for more information.
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.It "-- file unchanged"
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No savings is achieved by
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compression. The input remains virgin.
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.El
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.Sh FILES
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.Bl -tag -width file.Z
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.It Pa file.Z
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compressed file is file.Z
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.El
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.Sh BUGS
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Although compressed files are compatible between machines with large memory,
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.Fl b Ns Ar 12
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should be used for file transfer to architectures with
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a small process data space (64KB or less, as exhibited by the
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.Tn DEC PDP
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series, the Intel 80286, etc.)
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.Pp
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.Nm Compress
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should be more flexible about the existence of the `.Z' suffix.
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The
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.Nm compress
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utility exits 0 on success, and >0 if an error occurs.
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.Sh SEE ALSO
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.Rs
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.%A Welch, Terry A.
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.%D June, 1984
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.%T "A Technique for High Performance Data Compression"
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.%J "IEEE Computer"
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.%V 17:6
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.%P pp. 8-19
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.Re
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.Sh HISTORY
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The
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.Nm
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File diff suppressed because it is too large
Load Diff
@ -1,9 +1,6 @@
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/*
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* $Header: /cvsroot/src/usr.bin/compress/doc/revision.log,v 1.1.1.1 1993/03/21 09:45:37 cgd Exp $
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* $Log: revision.log,v $
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* Revision 1.1.1.1 1993/03/21 09:45:37 cgd
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* initial import of 386bsd-0.1 sources
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*
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* $Hdr: compress.c,v 4.0 85/07/30 12:50:00 joe Release $
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* $Lg: compress.c,v $
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* Revision 4.0 85/07/30 12:50:00 joe
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* Removed ferror() calls in output routine on every output except first.
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* Prepared for release to the world.
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@ -116,4 +113,4 @@
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*/
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static char rcs_ident[] =
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"$Header: /cvsroot/src/usr.bin/compress/doc/revision.log,v 1.1.1.1 1993/03/21 09:45:37 cgd Exp $";
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"$Hdr: compress.c,v 4.0 85/07/30 12:50:00 joe Release $";
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@ -31,7 +31,8 @@
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# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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# SUCH DAMAGE.
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#
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# @(#)zcat.sh 8.1 (Berkeley) 6/6/93
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# from: @(#)zcat.sh 8.1 (Berkeley) 6/6/93
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# $Id: zcat.sh,v 1.2 1994/06/13 14:48:36 cgd Exp $
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#
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uncompress -c $*
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@ -29,7 +29,8 @@
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)zopen.3 8.1 (Berkeley) 6/9/93
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.\" from: @(#)zopen.3 8.1 (Berkeley) 6/9/93
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.\" $Id: zopen.3,v 1.2 1994/06/13 14:48:40 cgd Exp $
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.\"
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.Dd June 9, 1993
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.Dt ZOPEN 3
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@ -36,7 +36,8 @@
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)zopen.c 8.1 (Berkeley) 6/27/93";
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/* from: static char sccsid[] = "@(#)zopen.c 8.1 (Berkeley) 6/27/93"; */
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static char *rcsid = "$Id: zopen.c,v 1.2 1994/06/13 14:48:44 cgd Exp $";
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#endif /* LIBC_SCCS and not lint */
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/*-
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