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Diffstat (limited to 'doc/zutils.texi')
| -rw-r--r-- | doc/zutils.texi | 33 |
1 files changed, 20 insertions, 13 deletions
diff --git a/doc/zutils.texi b/doc/zutils.texi index 34c15b4..ea9fb2d 100644 --- a/doc/zutils.texi +++ b/doc/zutils.texi @@ -6,8 +6,8 @@ @finalout @c %**end of header -@set UPDATED 15 May 2016 -@set VERSION 1.5 +@set UPDATED 5 April 2017 +@set VERSION 1.6 @dircategory Data Compression @direntry @@ -42,14 +42,14 @@ This manual is for Zutils (version @value{VERSION}, @value{UPDATED}). * Zcmp:: Comparing compressed files byte by byte * Zdiff:: Comparing compressed files line by line * Zgrep:: Searching inside compressed files -* Ztest:: Testing integrity of compressed files +* Ztest:: Testing the integrity of compressed files * Zupdate:: Recompressing files to lzip format * Problems:: Reporting bugs * Concept index:: Index of concepts @end menu @sp 1 -Copyright @copyright{} 2009-2016 Antonio Diaz Diaz. +Copyright @copyright{} 2009-2017 Antonio Diaz Diaz. This manual is free documentation: you have unlimited permission to copy, distribute and modify it. @@ -84,9 +84,9 @@ makes them safe to use with zutils. Gzip and xz may return ambiguous warning values, making them less reliable back ends for zutils. @xref{compressor-requirements}. -FORMAT NOTE: The @samp{--format} option allows the processing of a -subset of formats in search and recursive modes: -@w{@samp{zgrep foo -r --format=bz2,lz somedir}}. +FORMAT NOTE 1: The @samp{--format} option allows the processing of a +subset of formats in recursive mode and when trying compressed file +names: @w{@samp{zgrep foo -r --format=bz2,lz somedir somefile.tar}}. FORMAT NOTE 2: If the @samp{--force-format} option is given, the files are passed to the corresponding decompressor without verifying their @@ -94,7 +94,7 @@ format, allowing for example the processing of compress'd (.Z) files with gzip: @w{@samp{zcmp --force-format=gz file.Z file.lz}}. LANGUAGE NOTE: Uncompressed = not compressed = plain data; it may never -have been compressed. Decompressed is used to refer to data which has +have been compressed. Decompressed is used to refer to data which have undergone the process of decompression. @sp 1 @@ -224,7 +224,7 @@ exist, and its name does not end with one of the known extensions, zcat tries the compressed file names corresponding to the supported formats. If no files are specified, or if a file is specified as @samp{-}, data -is read from standard input, decompressed if needed, and sent to +are read from standard input, decompressed if needed, and sent to standard output. Data read from standard input must be of the same type; all uncompressed or all in the same compression format. @@ -349,7 +349,7 @@ for "meta"). @itemx --ignore-initial=@var{size} Ignore any differences in the first @var{size} bytes of the input files. Treat files with fewer than @var{size} bytes as if they were empty. If -@var{size} is in the form @samp{@var{size1},@var{size2}}, ignore the +@var{size} is in the form @samp{@var{size1}:@var{size2}}, ignore the first @var{size1} bytes of the first input file and the first @var{size2} bytes of the second input file. @@ -511,7 +511,7 @@ extensions, zgrep tries the compressed file names corresponding to the supported formats. If no files are specified, or if a file is specified as @samp{-}, data -is read from standard input, decompressed if needed, and fed to grep. +are read from standard input, decompressed if needed, and fed to grep. Data read from standard input must be of the same type; all uncompressed or all in the same compression format. @@ -657,8 +657,15 @@ is specified as @samp{-}, the integrity of compressed data read from standard input is verified. Data read from standard input must be all in the same compression format. -Note that some xz files lack integrity information, and therefore can't -be verified as reliably as the other formats can. +Note that error detection in the xz format is broken. First, some xz +files lack integrity information. Second, not all xz decompressors can +@uref{http://www.nongnu.org/lzip/xz_inadequate.html#fragmented,,verify the integrity} +of all xz files. Third, section 2.1.1.2 'Stream Flags' of the +@uref{http://tukaani.org/xz/xz-file-format.txt,,xz format specification} +allows xz decompressors to produce garbage output without issuing any +warning. Therefore, xz files can't always be verified as reliably as +files in the other formats can. +@c We can only hope that xz is soon abandoned. The format for running ztest is: |