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Document ‘cp’ limitations better

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* doc/autoconf.texi (Limitations of Usual Tools):
Modernize discussion of ‘cp’.
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Paul Eggert 2024-02-03 21:37:49 -08:00
parent 3a813b3b2f
commit 163dade069
1 changed files with 3 additions and 22 deletions
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@ -19288,28 +19288,9 @@ newline encoding.
@item @command{cp}
@c ---------------
@prindex @command{cp}
Avoid the @option{-r} option, since Posix 1003.1-2004 marks it as
obsolescent and its behavior on special files is implementation-defined.
Use @option{-R} instead. On GNU hosts the two options
are equivalent, but on Solaris hosts (for example) @code{cp -r}
reads from pipes instead of replicating them. AIX 5.3 @code{cp -R} may
corrupt its own memory with some directory hierarchies and error out or
dump core:
@example
@kbd{mkdir -p 12345678/12345678/12345678/12345678}
@kbd{touch 12345678/12345678/x}
@kbd{cp -R 12345678 t}
cp: 0653-440 12345678/12345678/: name too long.
@end example
Some @command{cp} implementations (e.g., BSD/OS 4.2) do not allow
trailing slashes at the end of nonexistent destination directories. To
avoid this problem, omit the trailing slashes. For example, use
@samp{cp -R source /tmp/newdir} rather than @samp{cp -R source
/tmp/newdir/} if @file{/tmp/newdir} does not exist.
The @option{-f} option is portable nowadays.
The @option{-i}, @option{-f}, @option{-p} and @option{-R} options are
widely used. POSIX also specifies @option{-H}, @option{-L}, and
@option{-P}. Avoid other options in portable scripts.
@cindex timestamp resolution
Traditionally, file timestamps had 1-second resolution, and @samp{cp