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head    display lines at the start of the file
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$ head -n lines -c bytes file1 file2 ...
where n is the number of lines to dispaly or the number of bytes to display.
The default value of n is 10

You can simplify to

$ head -5 file1   #show first five lines
$ head file1      #show, by default, first 10 lines

For Unix aficionados 

$ sed '5q' file1      #quite clever
$ sed 5q file1        #elegant & clever save two key strokes
$ awk 'NR<6' file1    #not elegant