The Annoyance Filter.pdf - Fourmilab

116 MAIL FOLDER ANNOYANCE-FILTER §132
132. The type of compression and command required to expand compressed files may differ from
system to system. The following code, conditional based on variables determined by the autoconf
process, defines the file suffix denoting a compressed file and the corresponding command used to
decode it. We only support one type of compression on a given system; if gzip is available, we use it in
preference to compress.
〈 Configure compression suffix and command 132 〉 ≡
#ifdef HAVE_POPEN
#if (defined HAVE_GUNZIP) ∨ (defined HAVE_GZCAT) ∨ (defined HAVE_GZIP)
# define COMPRESSED_FILES
static const char Compressed file type [ ] = ".gz";
static const char Uncompress command [ ] =
# if (defined HAVE_GUNZIP)
"gunzip␣−c"
# elif (defined HAVE_GZCAT)
"gzcat"
# elif (defined HAVE_GZIP)
"gzip␣−cd"
# endif
;
#elif (defined HAVE_ZCAT) ∨ (defined HAVE_UNCOMPRESS) ∨ (defined HAVE_COMPRESS)
# define COMPRESSED_FILES
static const char Compressed file type [ ] = ".Z";
#endif
#endif
static const char Uncompress command [ ] =
# if (defined HAVE_ZCAT)
"zcat"
# elif (defined HAVE_UNCOMPRESS)
"uncompress␣−c"
# elif (defined HAVE_COMPRESS)
"compress␣−cd"
# endif
;
This code is used in section 129.