Getting the index of the substring on solaris

Question

Hi. How can I find the index of a substring which matches a regular expression on solaris10?

Answer 1

The goto options for me are bash, awk and perl. I'm not sure what you're trying to do, but any of the three would likely work well. For example:

f=somestring
string=$(expr match "$f" '.*\(expression\).*')
echo $string

Answer 2

You tagged the question as bash, so I'm going to assume you're asking how to do this in a bash script. Unfortunately, the built-in regular expression matching doesn't save string indices. However, if you're asking this in order to extract the match substring, you're in luck:

if [[ "$var" =~ "$regex" ]]; then
     n=${#BASH_REMATCH[*]}
     while [[ $i -lt $n ]]
     do
         echo "capture[$i]: ${BASH_REMATCH[$i]}"
        let i++
     done
fi

This snippet will output in turn all of the submatches. The first one (index 0) will be the entire match.

You might like your awk options better, though. There's a function match which gives you the index you want. Documentation can be found here. It'll also store the length of the match in RLENGTH, if you need that. To implement this in a bash script, you could do something like:

match_index=$(echo "$var_to_search" | \
awk '{
    where = match($0, '"$regex_to_find"')
    if (where)
        print where
    else
        print -1
}')

There are a lot of ways to deal with passing the variables in to awk. This combination of piping output and directly embedding one into the awk one-liner is fairly common. You can also give awk variable values with the -v option (see man awk).

Obviously you can modify this to get the length, the match string, whatever it is you need. You can capture multiple things into an array variable if necessary:

match_data=($( ... awk '{ ... print where,RLENGTH,match_string ... }'))

Answer 3

Assuming that what you want is to find the location of the first match of a wildcard in a string using bash, the following bash function returns just that, or empty if the wildcard doesn't match:

function match_index()
{
  local pattern=$1
  local string=$2  
  local result=${string/${pattern}*/}

  [ ${#result} = ${#string} ] || echo ${#result}
}

For example:

$ echo $(match_index "a[0-9][0-9]" "This is a a123 test")
10

If you want to allow full-blown regular expressions instead of just wildcards, replace the "local result=" line with

local result=$(echo "$string" | sed 's/'"$pattern"'.*$//')

but then you're exposed to the usual shell quoting issues.

Answer 4

If you use bash 4.x you can source the oobash. A string lib written in bash with oo-style:

http://sourceforge.net/projects/oobash/

String is the constructor function:

String a abcda

a.indexOf a

0

a.lastIndexOf a

4

a.indexOf da

3

There are many "methods" more to work with strings in your scripts:

-base64Decode      -base64Encode  -capitalize        -center            
-charAt            -concat        -contains          -count             
-endsWith          -equals        -equalsIgnoreCase  -reverse           
-hashCode          -indexOf       -isAlnum           -isAlpha           
-isAscii           -isDigit       -isEmpty           -isHexDigit        
-isLowerCase       -isSpace       -isPrintable       -isUpperCase       
-isVisible         -lastIndexOf   -length            -matches           
-replaceAll        -replaceFirst  -startsWith        -substring         
-swapCase          -toLowerCase   -toString          -toUpperCase       
-trim              -zfill