grep: Introduction

 
 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.