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Diff for /src/usr.bin/compress/compress.1 between version 1.7 and 1.8

version 1.7, 1999/06/05 01:21:22 version 1.8, 1999/07/04 11:53:52
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 .Os  .Os
 .Sh NAME  .Sh NAME
 .Nm compress ,  .Nm compress ,
 .\".Nm uncompress ,  
 .Nm uncompress  .Nm uncompress
 .\".Nm zcat  
 .Nd compress and expand data  .Nd compress and expand data
 .Sh SYNOPSIS  .Sh SYNOPSIS
 .Nm compress  .Nm compress
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 .Op Fl cftoqv  .Op Fl cftoqv
 .Op Fl o Ar filename  .Op Fl o Ar filename
 .Op Ar  .Op Ar
 .\".Nm zcat  
 .\".Op Ar  
 .Sh DESCRIPTION  .Sh DESCRIPTION
 .Nm compress  .Nm
 reduces the size of the named files using adaptive Lempel-Ziv coding.  reduces the size of the named files using adaptive Lempel-Ziv coding.
 Each  Each
 .Ar file  .Ar file
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 files by deleting the  files by deleting the
 .Dq .Z  .Dq .Z
 extension.  extension.
 .\".Pp  
 .\".Nm Zcat  
 .\"is an alias for  
 .\".Dq "uncompress -c" .  
 .Pp  .Pp
 If renaming the files would cause files to be overwritten and the standard  If renaming the files would cause files to be overwritten and the standard
 input device is a terminal, the user is prompted (on the standard error  input device is a terminal, the user is prompted (on the standard error
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 Print the percentage reduction of each file.  Print the percentage reduction of each file.
 .El  .El
 .Pp  .Pp
 .Nm compress  .Nm
 uses a modified Lempel-Ziv algorithm.  uses a modified Lempel-Ziv algorithm.
 Common substrings in the file are first replaced by 9-bit codes 257 and up.  Common substrings in the file are first replaced by 9-bit codes 257 and up.
 When code 512 is reached, the algorithm switches to 10-bit codes and  When code 512 is reached, the algorithm switches to 10-bit codes and
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 After the  After the
 .Ar bits  .Ar bits
 limit is reached,  limit is reached,
 .Nm compress  .Nm
 periodically checks the compression ratio.  periodically checks the compression ratio.
 If it is increasing,  If it is increasing,
 .Nm compress  .Nm
 continues to use the existing code dictionary.  continues to use the existing code dictionary.
 However, if the compression ratio decreases,  However, if the compression ratio decreases,
 .Nm compress  .Nm
 discards the table of substrings and rebuilds it from scratch.  This allows  discards the table of substrings and rebuilds it from scratch.  This allows
 the algorithm to adapt to the next "block" of the file.  the algorithm to adapt to the next
   .Dq block
   of the file.
 .Pp  .Pp
 The  The
 .Fl b  .Fl b
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 time to compute.  time to compute.
 .Pp  .Pp
 The  The
 .Nm compress  .Nm
 utility exits 0 on success, 1 if an error occurred, or 2 if one or  utility exits 0 on success, 1 if an error occurred, or 2 if one or
 more files were not compressed because they would have grown in  more files were not compressed because they would have grown in
 size (and  size (and
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 .Re  .Re
 .Sh STANDARDS  .Sh STANDARDS
 The  The
 .Nm compress  .Nm
 utility is compliant with the  utility is compliant with the
 .St -p1003.2-92  .St -p1003.2-92
 specification.  specification.
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Removed from v.1.7  
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