Question

I am parsing a text file and I get multiple lines in the form shown below.

Then I try to split each line to three segments: Part1: sf; part2: name; part3:direction.

But now I am encountering difficulty in how to write my regular expression. I have thought about splitting on whitespace and using an array to concatenate new strings:

S15,F49  Large Recipe Download Request (LRDR)   S,H->E,reply

my ($sf, $name, $direction) =~ / I don't know how to implement here/

How can I get $sf = S15,F49 // other lines like S1,F11; S6,F1; etc

$name = Large Recipe Download Request (LRDR) // different name for different $sf.

$direction = S,H->E,reply; // some time it is M,H<-E,reply or S,H<->E or S,H->E,[reply], etc. There is no white space between each of sub items for part3: $direction

Answer 1

If there is no whitespace within the $sf and the $direction items, then you could apply the following code to each line:

if ($subject =~ m/^(\S+)\s+(.*?)\s+(\S+)$/) {
    $sf = $1;
    $name = $2;
    $direction = $3;
} else {
    // no match found
}

Explanation:

^: Anchor the regex at the start of the string.

(\S+): Match one or more non-space characters. Capture the match in $1.

\s+: Match one or more space characters (= separator(s) to the next item).

(.*?): Match any number of characters, as few as possible to still allow the overall match to succeed, and capture that in $2.*

\s+(\S+): Similar to the above – match space separator(s) and non-space characters –> $3.

$: Anchor the search at the end of the string.

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*The reason for the lazy quantifier *? is that otherwise, this part of the regex would also capture all the following space separators except the last one.