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| -rw-r--r-- | doc/coreutils.texi | 23 |
1 files changed, 14 insertions, 9 deletions
diff --git a/doc/coreutils.texi b/doc/coreutils.texi index a98c674e3..7068fc487 100644 --- a/doc/coreutils.texi +++ b/doc/coreutils.texi @@ -2552,15 +2552,20 @@ Always print file name headers. @end table On older systems, @command{tail} supports an obsolete option -@option{-@var{count}@var{options}}, which is recognized only if it is -specified first. @var{count} is a decimal number optionally followed -by a size letter (@samp{b}, @samp{k}, @samp{m}) as in @option{-c}, or -@samp{l} to mean count by lines, or other option letters -(@samp{cfqv}). Some older @command{tail} implementations also support -an obsolete option @option{+@var{count}} with the same meaning as -@option{-+@var{count}}. @acronym{POSIX} 1003.1-2001 (@pxref{Standards -conformance}) does not allow these options; use @option{-c -@var{count}} or @option{-n @var{count}} instead. +@option{-@var{count}[bcl][f]}, which is recognized only if it is +specified first. @var{count} is an optional decimal number optionally +followed by a size letter (@samp{b}, @samp{c}, @samp{l}) to mean count +by 512-byte blocks, bytes, or lines, optionally followed by @samp{f} +which has the same meaning as @option{-f}. Also, the leading @samp{-} +can be replaced by @samp{+} with the same meaning as in counts. +@acronym{POSIX} 1003.1-2001 (@pxref{Standards conformance}) does not +allow most of these obsolete usages; use @option{-c @var{count}[b]}, +@option{-n @var{count}}, and/or @option{-f} instead. + +On older systems, obsolete usage overrides normal usage, so portable +shell scripts should avoid commands that can be interpreted either +way. For example, use @samp{tail -- - file} rather than @samp{tail - +file}, and use @samp{tail -c4} rather than @samp{tail -c 4}. @exitstatus |