Check whether a string contains a substring

Question

How can I check whether a given string contains a certain substring  using Perl   More specifically  I want to see whether s1 domain com is present in the given string variable

User · Answer

Another possibility is to use regular expressions which is what Perl is famous for:

if ($mystring =~ /s1\.domain\.com/) {
   print qq("$mystring" contains "s1.domain.com"\n);
}

The backslashes are needed because a . can match any character. You can get around this by using the \Q and \E operators.

my $substring = "s1.domain.com";
    if ($mystring =~ /\Q$substring\E/) {
   print qq("$mystring" contains "$substring"\n);
}

Or, you can do as eugene y stated and use the index function. Just a word of warning: Index returns a -1 when it can't find a match instead of an undef or 0.

Thus, this is an error:

my $substring = "s1.domain.com";
if (not index($mystring, $substr)) {
    print qq("$mystring" doesn't contains "$substring"\n";
}

This will be wrong if s1.domain.com is at the beginning of your string. I've personally been burned on this more than once.

User · Answer

To find out if a string contains substring you can use the index function   if  index  str   substr     -1        print   str contains  substr n        It will return the position of the first occurrence of  substr in  str  or -1 if the substring is not found

User · Answer

Case Insensitive Substring Example  This is an extension of Eugene s answer  which converts the strings to lower case before checking for the substring   if  index lc  str   lc  substr      -1        print   str contains  substr n

[string] Check whether a string contains a substring

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