Grep is the name of an originally Unix command line interface program that searches files for the occurrence of a requested regular expression.
By default, grep receives regular expression as an argument and reads default input or list of files; Each line where regular expression is true is printed.
The name is from the form of a query in the Unix text editor, which has the form: g/re/p
and represents global / regular expression / print rules for which expression is true. Grep can also be seen as abbreviation: Global Regular Expression Parser.
With the help of several arguments, the default behavior of grep is changed.
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