coreutils: tac invocation

1 
1 3.2 ‘tac’: Concatenate and write files in reverse
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1 
1 ‘tac’ copies each FILE (‘-’ means standard input), or standard input if
1 none are given, to standard output, reversing the records (lines by
1 default) in each separately.  Synopsis:
1 
1      tac [OPTION]... [FILE]...
1 
1    “Records” are separated by instances of a string (newline by
1 default).  By default, this separator string is attached to the end of
1 the record that it follows in the file.
1 
11    The program accepts the following options.  Also see ⇒Common
 options.
1 
1 ‘-b’
1 ‘--before’
1      The separator is attached to the beginning of the record that it
1      precedes in the file.
1 
1 ‘-r’
1 ‘--regex’
1      Treat the separator string as a regular expression.
1 
1 ‘-s SEPARATOR’
1 ‘--separator=SEPARATOR’
1      Use SEPARATOR as the record separator, instead of newline.  Note an
1      empty SEPARATOR is treated as a zero byte.  I.e., input and output
1      items are delimited with ASCII NUL.
1 
1    On systems like MS-DOS that distinguish between text and binary
1 files, ‘tac’ reads and writes in binary mode.
1 
1    An exit status of zero indicates success, and a nonzero value
1 indicates failure.
1 
1    Example:
1 
1      # Reverse a file character by character.
1      tac -r -s 'x\|[^x]'
1