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# 1  
Old 01-07-2016
Grep
my file has one line
Code:
abcdedabxxxxabxxxab

I want to know the #occurrences of substring ab and their positions

Following command gives me

Code:
 >grep ab -o file|wc
 4       4      12

Is the first 4, the number of occurrences of ab? what are other numbers.
Can I get their positions in a one liners?
thanks
Last edited by Don Cragun; 01-07-2016 at 04:58 PM.. Reason: Add CODE and ICODE tags.
# 2  
Old 01-07-2016
man wc:
Quote:
DESCRIPTION
Print newline, word, and byte counts ...
If your awk allows for multichar field separators, try
Code:
awk -F"ab" '{L = length(FS); T = -1; for (i=1; i<NF; i++) print T += length($i) +  L}' file1
1
7
13
18

# 3  
Old 01-07-2016
Short answer is no. The first number 4 is the offset (-b) for GNU grep.

You can use sed with grep, but it is somewhat awkward. Another approach is awk.
(nawk is solaris)
Code:
  nawk '{
             while (length($0)>=2)
             {
               lcnt++
               if(substr($0,1,2)=="ab")
               {
                  print "position", lcnt
                  count++
               }
               $0=substr($0,2)
              }
            }
        END {print count, "occurences"} ' infile

My data file: $ cat infile
Code:
abedcabsabwqsab

# 4  
Old 01-07-2016
thanks a ton, this is exactly what I was looking for.
# 5  
Old 01-07-2016
Quote:
Originally Posted by RudiC
man wc:

If your awk allows for multichar field separators, try
Code:
awk -F"ab" '{L = length(FS); T = -1; for (i=1; i<NF; i++) print T += length($i) +  L}' file1
1
7
13
18

I think every version of awk allows FS to be set to:
  • a single character (using that single character as the field separator), and
  • a multi-character extended regular expression (using every string matching that ERE as the field separator).
Some implementations of awk allow FS to be set to an empty string to treat each character in an input record as a field.

The standards only specify the behavior of awk when RS (not FS) is a single character. Some versions of awk also treat a multi-character string in RS to use any string matching the ERE specified by that multi-character string to be used as the input record separator; others only use the first character of RS as the record separator.
# 6  
Old 01-09-2016
Quote:
Originally Posted by prak705
my file has one line
Code:
abcdedabxxxxabxxxab

In such a case (notice: ONLY in such a case, where the content is only one line long) one might be better off without using any external programs. One can do what you want to do with shell built-ins only (i use ksh93 here):

Code:
search="ab"                  # our search string
var=$(</path/to/file)        # read the file content into a variable
print - ${#var}              # display the length of the string
varnew=${var//${search}/}    # remove every instance of the search string from the content and store the result

print - $(( ( ${#var} - ${#varnew} ) / ${#search} ))

The last line takes the difference in length before and after removal of the search string and divides the result by the length of the search string, getting the number of occurences.

I haven't tested the execution speed yet but my prediction is that it is much faster than a call to awk or any other external tool.

I hope this helps.

bakunin
# 7  
Old 01-09-2016
@bakunin, wouldn't you need a loop to get the positions?
 
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