Using piped commands to get a specific output in Bash

Question

I'm following a programming course and I'm trying to do a practice activity but I'm stuck. I have a file with the following list:

Monday       day
Tuesday      day
Easter       holiday
Monday       day
christmas    holiday
Tuesday      day
Friday       day
Thursday     day
thanksgiving holiday

What I'm trying to do is

sorting this list,
printing a new list containing only those names that are not repeated,
counting the number of times each word appears in the list, and
inserting a tab between the counter and the word.

This would be my desired output:

1    christmas    holiday
1    Easter       holiday
1    Friday       day
2    Monday       day
1    thanksgiving holiday
1    Thursday     day
2    Tuesday      day

I have tried using the following line of code:

cat my_file | sort | uniq -c | less

My problem is that words are not really sorted because words starting with capital letters would come before words starting with lowercase letters. Also, I don't know how to add the tab between the number and the word (in my output, there's only a space between them).

Could you help me?

You need to sort giving the key to do e.g. sort -k1 file | uniq -c | column -t should solve your problem. Here -k1 arg to sort specifies sorting based on first column — Inian
– Inian, Commented Oct 10, 2018 at 5:04

clemens · Accepted Answer · 2018-10-10 05:14:24Z

2

You may use -f to sort case-insensitive, and replacing spaces with tabs with sed(1). cat my be omitted from the pipe:

sort -f my_file | uniq -c | sed $'s/  */\t/g' | less

Note: The dollar sign in front of the sed parameter interprets \t as tab and not as \t.

If the first tab in each line is annoying, you can remove it with sed as well:

sort -f my_file | uniq -c | sed 's/^ *//' | sed $'s/  */\t/g' | less

This produces:

1   christmas   holiday
1   Easter  holiday
1   Friday  day
2   Monday  day
1   thanksgiving    holiday
1   Thursday    day
2   Tuesday day

Finally, if you want to keep spaces between the second an the third column, you should omit the g (replace all occurences of the search pattern) from the second sed invocation:

sort -f my_file | uniq -c | sed 's/ *//' | sed $'s/  */\t/' | less

Result:

1   christmas    holiday
1   Easter       holiday
1   Friday       day
2   Monday       day
1   thanksgiving holiday
1   Thursday     day
2   Tuesday      day

edited Oct 10, 2018 at 5:14

answered Oct 10, 2018 at 5:09

clemens

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8 Comments

Benjamin W. Over a year ago

Many sed insert a tab when you use \t in the substitution string; for example, GNU sed does.

clemens Over a year ago

I have now tested \t on Ubuntu where it works, but this doesn't work on macOS. It's probably a GNU extension.

Benjamin W. Over a year ago

Yes, POSIX doesn't prescribe what to do with backslash escapes in the replacement string (other than \& and \1/\2 etc.)

Me All Over a year ago

This works, though there's one problem: I get the number and word together and the first tab comes before the number itself. How could I change that?

Me All Over a year ago

This is an example of what I got: (tab) 1 christmas holiday , and this is what I want: 1 christmas holiday

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