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diff --git a/man-pages-posix-2017/man1p/compress.1p b/man-pages-posix-2017/man1p/compress.1p new file mode 100644 index 0000000..8c2b47a --- /dev/null +++ b/man-pages-posix-2017/man1p/compress.1p @@ -0,0 +1,260 @@ +'\" et +.TH COMPRESS "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual" +.\" +.SH PROLOG +This manual page is part of the POSIX Programmer's Manual. +The Linux implementation of this interface may differ (consult +the corresponding Linux manual page for details of Linux behavior), +or the interface may not be implemented on Linux. +.\" +.SH NAME +compress +\(em compress data +.SH SYNOPSIS +.LP +.nf +compress \fB[\fR-fv\fB] [\fR-b \fIbits\fB] [\fIfile\fR...\fB]\fR +.P +compress \fB[\fR-cfv\fB] [\fR-b \fIbits\fB] [\fIfile\fB]\fR +.fi +.SH DESCRIPTION +The +.IR compress +utility shall attempt to reduce the size of the named files by using +adaptive Lempel-Ziv coding algorithm. +.TP 10 +.BR Note: +Lempel-Ziv is US Patent 4464650, issued to William Eastman, Abraham +Lempel, Jacob Ziv, Martin Cohn on August 7th, 1984, and assigned to +Sperry Corporation. +.RS 10 +.P +Lempel-Ziv-Welch compression is covered by US Patent 4558302, issued to +Terry A. Welch on December 10th, 1985, and assigned to Sperry +Corporation. +.RE +.P +On systems not supporting adaptive Lempel-Ziv coding algorithm, the +input files shall not be changed and an error value greater than two +shall be returned. Except when the output is to the standard output, +each file shall be replaced by one with the extension +.BR .Z . +If the invoking process has appropriate privileges, the ownership, +modes, access time, and modification time of the original file are +preserved. If appending the +.BR .Z +to the filename would make the name exceed +{NAME_MAX} +bytes, the command shall fail. If no files are specified, the standard +input shall be compressed to the standard output. +.SH OPTIONS +The +.IR compress +utility shall conform to the Base Definitions volume of POSIX.1\(hy2017, +.IR "Section 12.2" ", " "Utility Syntax Guidelines". +.P +The following options shall be supported: +.IP "\fB\-b\ \fIbits\fR" 10 +Specify the maximum number of bits to use in a code. For a conforming +application, the +.IR bits +argument shall be: +.RS 10 +.sp +.RS 4 +.nf + +9 <= \fIbits\fP <= 14 +.fi +.P +.RE +.P +The implementation may allow +.IR bits +values of greater than 14. The default is 14, 15, or 16. +.RE +.IP "\fB\-c\fP" 10 +Cause +.IR compress +to write to the standard output; the input file is not changed, and no +.BR .Z +files are created. +.IP "\fB\-f\fP" 10 +Force compression of +.IR file , +even if it does not actually reduce the size of the file, or if the +corresponding +.IR file \c +.BR .Z +file already exists. If the +.BR \-f +option is not given, and the process is not running in the background, +the user is prompted as to whether an existing +.IR file \c +.BR .Z +file should be overwritten. If the response is affirmative, the existing +file will be overwritten. +.IP "\fB\-v\fP" 10 +Write the percentage reduction of each file to standard error. +.SH OPERANDS +The following operand shall be supported: +.IP "\fIfile\fR" 10 +A pathname of a file to be compressed. +.SH STDIN +The standard input shall be used only if no +.IR file +operands are specified, or if a +.IR file +operand is +.BR '\-' . +.SH "INPUT FILES" +If +.IR file +operands are specified, the input files contain the data to be +compressed. +.SH "ENVIRONMENT VARIABLES" +The following environment variables shall affect the execution of +.IR compress : +.IP "\fILANG\fP" 10 +Provide a default value for the internationalization variables that are +unset or null. (See the Base Definitions volume of POSIX.1\(hy2017, +.IR "Section 8.2" ", " "Internationalization Variables" +for the precedence of internationalization variables used to determine +the values of locale categories.) +.IP "\fILC_ALL\fP" 10 +If set to a non-empty string value, override the values of all the +other internationalization variables. +.IP "\fILC_COLLATE\fP" 10 +.br +Determine the locale for the behavior of ranges, equivalence classes, +and multi-character collating elements used in the extended regular +expression defined for the +.BR yesexpr +locale keyword in the +.IR LC_MESSAGES +category. +.IP "\fILC_CTYPE\fP" 10 +Determine the locale for the interpretation of sequences of bytes of text +data as characters (for example, single-byte as opposed to multi-byte +characters in arguments), the behavior of character classes used in the +extended regular expression defined for the +.BR yesexpr +locale keyword in the +.IR LC_MESSAGES +category. +.IP "\fILC_MESSAGES\fP" 10 +.br +Determine the locale used to process affirmative responses, and the +locale used to affect the format and contents of diagnostic messages, +prompts, and the output from the +.BR \-v +option written to standard error. +.IP "\fINLSPATH\fP" 10 +Determine the location of message catalogs for the processing of +.IR LC_MESSAGES . +.SH "ASYNCHRONOUS EVENTS" +Default. +.SH STDOUT +If no +.IR file +operands are specified, or if a +.IR file +operand is +.BR '\-' , +or if the +.BR \-c +option is specified, the standard output contains the compressed +output. +.SH STDERR +The standard error shall be used only for diagnostic and prompt +messages and the output from +.BR \-v . +.SH "OUTPUT FILES" +The output files shall contain the compressed output. The format of +compressed files is unspecified and interchange of such files between +implementations (including access via unspecified file sharing +mechanisms) is not required by POSIX.1\(hy2008. +.SH "EXTENDED DESCRIPTION" +None. +.SH "EXIT STATUS" +The following exit values shall be returned: +.IP "\00" 6 +Successful completion. +.IP "\01" 6 +An error occurred. +.IP "\02" 6 +One or more files were not compressed because they would have increased +in size (and the +.BR \-f +option was not specified). +.IP >2 6 +An error occurred. +.SH "CONSEQUENCES OF ERRORS" +The input file shall remain unmodified. +.LP +.IR "The following sections are informative." +.SH "APPLICATION USAGE" +The amount of compression obtained depends on the size of the input, +the number of +.IR bits +per code, and the distribution of common substrings. Typically, text +such as source code or English is reduced by 50\(hy60%. Compression is +generally much better than that achieved by Huffman coding +or adaptive Huffman coding (\c +.IR compact ), +and takes less time to compute. +.P +Although +.IR compress +strictly follows the default actions upon receipt of a signal or when +an error occurs, some unexpected results may occur. In some +implementations it is likely that a partially compressed file is left +in place, alongside its uncompressed input file. Since the general +operation of +.IR compress +is to delete the uncompressed file only after the +.BR .Z +file has been successfully filled, an application should always +carefully check the exit status of +.IR compress +before arbitrarily deleting files that have like-named neighbors with +.BR .Z +suffixes. +.P +The limit of 14 on the +.IR bits +option-argument is to achieve portability to all systems (within the +restrictions imposed by the lack of an explicit published file +format). Some implementations based on 16-bit architectures cannot +support 15 or 16-bit uncompression. +.SH EXAMPLES +None. +.SH RATIONALE +None. +.SH "FUTURE DIRECTIONS" +None. +.SH "SEE ALSO" +.IR "\fIuncompress\fR\^", +.IR "\fIzcat\fR\^" +.P +The Base Definitions volume of POSIX.1\(hy2017, +.IR "Chapter 8" ", " "Environment Variables", +.IR "Section 12.2" ", " "Utility Syntax Guidelines" +.\" +.SH COPYRIGHT +Portions of this text are reprinted and reproduced in electronic form +from IEEE Std 1003.1-2017, Standard for Information Technology +-- Portable Operating System Interface (POSIX), The Open Group Base +Specifications Issue 7, 2018 Edition, +Copyright (C) 2018 by the Institute of +Electrical and Electronics Engineers, Inc and The Open Group. +In the event of any discrepancy between this version and the original IEEE and +The Open Group Standard, the original IEEE and The Open Group Standard +is the referee document. The original Standard can be obtained online at +http://www.opengroup.org/unix/online.html . +.PP +Any typographical or formatting errors that appear +in this page are most likely +to have been introduced during the conversion of the source files to +man page format. To report such errors, see +https://www.kernel.org/doc/man-pages/reporting_bugs.html . |