Related cases of awk, the boss of the three Musketeers
awk {} curly brackets inside is action, outside is condition
NR==(number record)
If you do not enter numbers, default to all rows
2. Select columns---If you want to separate columns, add ", or other symbols"
Display oldboy.txt row 4 column 1 column 2 and column 4 awk default space is a separator, so the fourth column after together, a character default is a knife, unless added +,[]+ into the whole
The case first specifies the separator as space and comma-F"[ ,]", one symbol is equivalent to one knife
Remove IP address
Compare sizes
NF is the last column.
Check disk usage Both numbers and percent signs are not recognized
