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1 Introduction
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Given one or more patterns, ‘grep’ searches input files for matches to
the patterns.  When it finds a match in a line, it copies the line to
standard output (by default), or produces whatever other sort of output
you have requested with options.

   Though ‘grep’ expects to do the matching on text, it has no limits on
input line length other than available memory, and it can match
arbitrary characters within a line.  If the final byte of an input file
is not a newline, ‘grep’ silently supplies one.  Since newline is also a
separator for the list of patterns, there is no way to match newline
characters in a text.