I have 100 million rows in my file.

Each row has only one column.



I would like to list the character count

Like this

2 character words - 3
5 character words - 1
7 character words - 1


Is there any easy way to do this in terminal?

$ awk '{ print length }' file | sort -n | uniq -c | awk '{ printf("%d character words: %d\n", $2, $1) }'
2 character words: 3
5 character words: 1
7 character words: 1

The first awk filter will just print the length of each line in the file called file. I'm assuming that this file contains one word per line.

The sort -n (sort the lines from the output of awk numerically in ascending order) and uniq -c (count the number of times each line occurs consecutively) will then create the following output from that for the given data:

   3 2
   1 5
   1 7

This is then parsed by the second awk script which interprets each line as "X number of lines having Y characters" and produces the wanted output.

The alternative solution is to do it all in awk and keeping counts of lengths in an array. It's a tradeoff between efficiency, readability/ease of understanding (and therefore maintainability) which solution is the "best".

Alternative solution:

$ awk '{ len[length]++ } END { for (i in len) printf("%d character words: %d\n", i, len[i]) }' file
2 character words: 3
5 character words: 1
7 character words: 1
  • No need to sort in awk (numerically indexed arrays are sorted by default) (faster).
    – ImHere
    Oct 8 '17 at 18:14
  • @Arrow I know. I have that solution commented out in my answer because Sundeep beat me to it with a few seconds. I also allude to this with my last paragraph.
    – Kusalananda
    Oct 8 '17 at 18:18
  • I believe the comment should be useful to the users of the solutions (not included in your answer (or Sundeep's) :-) …). Otherwise: include a comment to the same effect in your answer and I happily will remove my comments. :-)
    – ImHere
    Oct 8 '17 at 18:25

Another way to do it all with awk alone

$ awk '{words[length()]++} END{for(k in words)print k " character words - " words[k]}' ip.txt 
2 character words - 3
5 character words - 1
7 character words - 1
  • words[length()]++ use length of input line as key to save count
  • END{for(k in words)print k " character words - " words[k]} after all lines are processed, print contents of array in desired format

Performance comparison, numbers selected are best of two runs

$ wc words.txt
 71813  71813 655873 words.txt
$ perl -0777 -ne 'print $_ x 1000' words.txt > long_file.txt
$ du -h --apparent-size long_file.txt
626M    long_file.txt

$ time awk '{words[length()]++} END{for(k in words)print k " character words - " words[k]}' long_file.txt > t1

real    0m20.632s
user    0m20.464s
sys     0m0.108s

$ time perl -lne '$h{length($_)}++ }{ for $n (sort keys %h) {print "$n character words - $h{$n}"}' long_file.txt > t2

real    0m19.749s
user    0m19.640s
sys     0m0.108s

$ time awk '{ print length }' long_file.txt | sort -n | uniq -c | awk '{ printf("%d character words - %d\n", $2, $1) }' > t3

real    1m23.294s
user    1m24.952s
sys     0m1.980s

$ diff -s <(sort t1) <(sort t2)
Files /dev/fd/63 and /dev/fd/62 are identical
$ diff -s <(sort t1) <(sort t3)
Files /dev/fd/63 and /dev/fd/62 are identical

If file has only ASCII characters,

$ time LC_ALL=C awk '{words[length()]++} END{for(k in words)print k " character words - " words[k]}' long_file.txt > t1

real    0m15.651s
user    0m15.496s
sys     0m0.120s

Not sure why time for perl didn't change much, probably encoding has to be set some other way

  • I just added that to my own solution. Deleted it when I saw your's though. :-)
    – Kusalananda
    Oct 8 '17 at 16:01
  • yeah I was debating to delete mine before saw your edit again :)
    – Sundeep
    Oct 8 '17 at 16:02
  • No need to sort a numerically indexed array. It is allways ordered with an increasing index. ( well, at least in awk :-) )
    – ImHere
    Oct 8 '17 at 18:09
  • length without () works perfectly fine here, so it might be redundant to add braces. I'm using GNU awk,though. Oct 8 '17 at 20:14
  • 2
    @SergiyKolodyazhnyy yup, gnu awk manual says In older versions of awk, the length() function could be called without any parentheses. Doing so is considered poor practice, although the 2008 POSIX standard explicitly allows it, to support historical practice. For programs to be maximally portable, always supply the parentheses
    – Sundeep
    Oct 9 '17 at 3:08

Here's a perl equivalent (with - optional - sort):

$ perl -lne '
    $h{length($_)}++ }{ for $n (sort keys %h) {print "$n character words - $h{$n}"}
' file
2 character words - 3
5 character words - 1
7 character words - 1
  • If keys indexes are numerical: Does keys array need to be sorted in Perl?
    – ImHere
    Oct 8 '17 at 19:13
  • 1
    @Arrow: This answer is using a hash (i.e. associative array with string keys), and those have undefined key order, so yes. In fact, the answer is slightly buggy because it's sorting the keys as strings, not as numbers. Adding {$a<=>$b} after the sort would fix that. Alternatively, one could use a normal array with numerical keys and just skip any keys where the value is zero / undefined. Oct 8 '17 at 23:41
  • @IlmariKaronen Thanks, better now. What a difference curly braces make !!
    – ImHere
    Oct 8 '17 at 23:52
  • It would be more efficient to use an array instead of a hash. The OP wants millions of lines, so any overhead of checking and skipping zeros while printing is easily made up for by cheaper indexing. Oct 9 '17 at 8:47

An alternative one call to GNU awk, using printf:

$ awk 'BEGIN { PROCINFO["sorted_in"] = "@ind_str_asc"}
           for(i in c){printf("%s character words - %s\n",i,c[i])}
          }' infile
2 character words - 3
5 character words - 1
7 character words - 1

The core algorithm just collects character counts in an array. The end part prints the collected counts formatted with printf.

Fast, simple, one single call to awk.

To be precise: some more memory is used to keep the array.
But no sort is called (numeric arrays indexes are set to be always traversed sorted upward with PROCINFO), and only one external program: awk, instead of several.

  • 1
    for in may happen to give numeric array indexes in numeric order at least for some values or in some awk implementations, but that is not required, not traditional, and definitely not universal. It does often happen for tiny sets like 2 or 3 or maybe 4; try 10 or 20 on every awk you have access to (without PROCINFO or WHINY_USERS in gawk) and I bet $50 at least one case isn't sorted. Oct 8 '17 at 23:47
  • Thanks for your input. Using this: I believe it is sorted now. :-)
    – ImHere
    Oct 9 '17 at 0:04
  • 1
    @ind_str_asc sorts as strings, which will be correct for numbers only if they are all single-digit (as your example is); use @ind_num_asc if (any) values can be 10 or more. And although it's less of an issue now than it used to be, this feature is only gawk 4.0 up. Oct 9 '17 at 4:27

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