Compression of Duplicate Lines
In the Unix programs od and hexdump, not all lines of display output that contain the same data as the previous line are shown; instead, a line containing just one asterisk is displayed. For example, a block of all zeros is printed as:
0000000 0000 0000 0000 0000 0000 0000 0000 0000 * 0000030This compression feature makes a useful tool for inspecting large files or complete devices for irregularities. In a modern Linux system, it is convenient to scan an entire hard drive to check if it is all blank:
# hexdump /dev/sda (replace sda with the proper name for the device to be scanned)The -v option causes hexdump and od to display all input data, explicitly:
0000000 0000 0000 0000 0000 0000 0000 0000 0000 0000010 0000 0000 0000 0000 0000 0000 0000 0000 0000020 0000 0000 0000 0000 0000 0000 0000 0000Read more about this topic: Hex Dump
Famous quotes containing the words compression, duplicate and/or lines:
“The triumphs of peace have been in some proximity to war. Whilst the hand was still familiar with the sword-hilt, whilst the habits of the camp were still visible in the port and complexion of the gentleman, his intellectual power culminated; the compression and tension of these stern conditions is a training for the finest and softest arts, and can rarely be compensated in tranquil times, except by some analogous vigor drawn from occupations as hardy as war.”
—Ralph Waldo Emerson (1803–1882)
“O Nature, and O soul of man! how far beyond all utterance are your linked analogies! not the smallest atom stirs or lives in matter, but has its cunning duplicate in mind.”
—Herman Melville (1819–1891)
“When first my lines of heavenly joys made mention,
Such was their luster, they did so excel,
That I sought out quaint words and trim invention;
My thoughts began to burnish, sprout, and swell,
Curling with metaphors a plain intention,
Decking the sense as if it were to sell.”
—George Herbert (1593–1633)