1.Word Frequency 統(tǒng)計詞頻

For example, assume that words.txt
has the following content:

the day is sunny the the
the sunny is is

Your script should output the following, sorted by descending frequency:

the 4
is 3
sunny 2
day 1

# Read from the file words.txt and output the word frequency list to stdout.
 awk '{i=1; while(i<=NF) {print $i; i++}}'  words.txt | sort | uniq -c | sort -k1nr | awk '{print $2 " " $1}'

2. Valid Phone Numbers 正則判斷是否有效

For example, assume that file.txt
has the following content:

987-123-4567
123 456 7890
(123) 456-7890

Your script should output the following valid phone numbers:

987-123-4567
(123) 456-7890

# Read from the file file.txt and output all valid phone numbers to stdout.
 cat file.txt | grep -Eo '^((\([0-9]{3}\)\s)|([0-9]{3}-))[0-9]{3}-[0-9]{4}$'

3. Transpose File 轉(zhuǎn)置文件

For example, if file.txt
has the following content:

name age
alice 21
ryan 30

Output the following:

name alice ryan
age 21 30

# Read from the file file.txt and print its transposed content to stdout.
awk '{
     for( i=0; i<=NF; i++) {
        if(NR == 1) s[i] = $i;
        else s[i]= s[i] " " $i;
     }
} END {
        for(i=1; s[i]!=""; i++)
                print s[i]

}' file.txt

4. Tenth Line 輸出第10行

# Read from the file file.txt and output the tenth line to stdout.
awk '{ if(NR == 10) print $0 }' file.txt