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| -rw-r--r-- | ChangeLog | 4 | ||||
| -rw-r--r-- | doc/coreutils.texi | 26 |
2 files changed, 30 insertions, 0 deletions
@@ -1,5 +1,9 @@ 2007-11-01 Jim Meyering <meyering@redhat.com> + Add example inspired by "make dist" running gzip and lzma in sequence. + * doc/coreutils.texi (tee invocation): Show how to run tar just + once, compressing the tee'd output streams in parallel. + Say that the first process substitution example is contrived. * doc/coreutils.texi (tee invocation): ... and show how to do it properly. Pointed out by James Antill. diff --git a/doc/coreutils.texi b/doc/coreutils.texi index 9c960a57e..4c08378ce 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -11136,6 +11136,32 @@ right away and eliminate the decompression completely: du -ak | tee >(gzip -9 > /tmp/du.gz) | xdiskusage -a @end example +Finally, if you regularly create more than one type of +compressed tarball at once, for example when @code{make dist} creates +both @command{gzip}-compressed and @command{bzip2}-compressed tarballs, +there may be a better way. +Typical @command{automake}-generated @file{Makefile} rules create +the two compressed tar archives with commands in sequence, like this +(slightly simplified): + +@example +tardir=your-pkg-M.N +tar chof - "$tardir" | gzip -9 -c > your-pkg-M.N.tar.gz +tar chof - "$tardir" | bzip2 -9 -c > your-pkg-M.N.tar.bz2 +@end example + +However, if the hierarchy you are archiving and compressing is larger +than a couple megabytes, and especially if you are using a multi-processor +system with plenty of memory, then you can do much better by reading the +directory contents only once and running the compression programs in parallel: + +@example +tardir=your-pkg-M.N +tar chof - "$tardir" \ + | tee >(gzip -9 -c > your-pkg-M.N.tar.gz) \ + | bzip2 -9 -c > your-pkg-M.N.tar.bz2 +@end example + @exitstatus |