195. Tenth Line

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

Line 1

Line 2

Line 3

Line 4

Line 5

Line 6

Line 7

Line 8

Line 9

Line 10

Your script should output the tenth line, which is:

Line 10

answer：sed -n '10p' file.txt

 

192. Word Frequency

Write a bash script to calculate the frequency of each word in a text file words.txt.

For simplicity sake, you may assume:

words.txt contains only lowercase characters and space ' ' characters.

Each word must consist of lowercase characters only.

Words are separated by one or more whitespace characters.

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

answer:cat words.txt | tr -s "\t| "  "\n" | sort |uniq -c |sort -k 1 -r|awk '{print $2,$1}'

 

194. Transpose File

Given a text file file.txt, transpose its content.

You may assume that each row has the same number of columns and each field is separated by the ' ' character.

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

name age

alice 21

ryan 30

Output the following:

name alice ryan

age 21 30

answer:awk '{for(i=1;i<=NF;i++) if(NR==1) a[i]=$i;else a[i]=(a[i]" "$i);} END{for (i in a) print a[i];}' file.txt  #这个解非原创

 

193. Valid Phone Numbers

Given a text file file.txt that contains list of phone numbers (one per line), write a one liner bash script to print all valid phone numbers.

You may assume that a valid phone number must appear in one of the following two formats: (xxx) xxx-xxxx or xxx-xxx-xxxx. (x means a digit)

You may also assume each line in the text file must not contain leading or trailing white spaces.

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

answer:grep  '^[0-9]\{3\}-[0-9]\{3\}-[0-9]\{4\}$\|^([0-9]\{3\})\s[0-9]\{3\}-[0-9]\{4\}$'  file.txt 

ps:{}需要进行转义\{\} ;()不需要转义;空格\s