CODEWITHSUNDEEP
linuxbashunixcommand-line
Wojciech K
Wojciech K

Reputation: 182

Count lines and group by prefix word

I want to count number of lines in a document and group it by the prefix word. Prefix is a set of alphanumeric characters delimited by first underscore. I don't care much about sorting them but it would be nice to list them descending by number of occurrences.

The file looks like this:

prefix1_data1
prefix1_data2_a
differentPrefix_data3
prefix1_data2_b
differentPrefix_data5
prefix2_data4
differentPrefix_data5

The output should be the following:

prefix1           3
differentPrefix   3
prefix2           1

I already did this in python but I am curious if it is possible to do this more efficient using command line or bash script? uniq command has -c and -w options but the length of prefix may vary.

Upvotes: 6

Views: 6586

Answers (4)

John Chesshir
John Chesshir

Reputation: 640

I like RomanPerekhrest's answer. It's more concise. Here is a small change to make it even more concise by using cut in place of sed.

cut -d_ -f1 testfile | sort | uniq -c

Upvotes: 2

RomanPerekhrest
RomanPerekhrest

Reputation: 92854

The solution using combination of sed, sort and uniq commands:

sed -rn 's/^([^_]+)_.*/\1/p' testfile | sort | uniq -c

The output:

3 differentPrefix
3 prefix1
1 prefix2

^([^_]+)_ - matches a sub-string(prefix, containing any characters except _) from the start of the string to the first occurrence of underscore _

Upvotes: 7

v_sukt
v_sukt

Reputation: 1442

Can be done in following manner, testfile is file with contents mentioned above.

printf %-20s%d"\n" prefix1 $(cat testfile|grep "^prefix1" | wc -l)
printf %-20s%d"\n" differentPrefix $(cat testfile|grep "^differentPrefix" | wc -l)
printf %-20s%d"\n" prefix2 $(cat testfile|grep "^prefix2" | wc -l)

so you can check this with your code and check which one's more efficient.

Upvotes: 0

oliv
oliv

Reputation: 13249

You could use awk:

awk -F_ '{a[$1]++}END{for(i in a) print i,a[i]}' file

The field separator is set to _.

An array a is filled with all first element, with their associated count.

When the file is parsed the array content is printed

Upvotes: 7

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