How can I check whether a given string contains a certain substring, using Perl?
More specifically, I want to see whether s1.domain.example is present in the given string variable.
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 $str, or -1 if the substring is not found.
Another possibility is to use regular expressions which is what Perl is famous for:
if ($mystring =~ /s1\.domain\.example/) {
print qq("$mystring" contains "s1.domain.example"\n);
}
The backslashes are needed because a . can match any character. You can get around this by using the \Q and \E operators.
my $substring = "s1.domain.example";
if ($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 $substring = "s1.domain.example";
if (not index($mystring, $substr)) {
print qq("$mystring" doesn't contains "$substring"\n";
}
This will be wrong if s1.domain.example is at the beginning of your string. I've personally been burned on this more than once.
Case Insensitive Substring Example
This is an extension of Eugene's answer, which converts the strings to lower case before checking for the substring:
if (index(lc($str), lc($substr)) != -1) {
print "$str contains $substr\n";
}
Related
I'm currently writing a groovy script that can extract characters based on the condition given, however I struggled extracting specific string after specific number of char. For example:
If (text = 'ABCDEF')
{
Return (start from C and print only CDE)
}
I already used substring but didn't give me the right output:
If (text = 'ABCDEF')
{
Return(text.substring(2));
}
Try this:
if (text == 'ABCDEF')
{
return text.substring(2, 5)
}
= is for assigning a value to a variable.
== is for checking equality between the two variable.
Your capitalization is all out of whack
if (text == 'ABCDEF') {
text.substring(2)
}
There's probably also issues with using return, but that depends on context you haven't shown in your question
Your substring function isn't complete. If you need to grab specific indices (in this case, index 2 to 5), you need to add the index you want to end at. If you don't do that, your string will print the string starting from index 2, and then the remaining characters in the string. You need to need to type this:
if(text == 'ABCDEF') {
return text.substring(2, 5);
}
Also, keep in mind that the end index (index 5) is exclusive, so the character at index 5 won't be printed.
I would like to check if a specific word is the last one in a string. (the string is the user input from a textfield)
What is a good way to do that?
I would use lastIndexOf():
function endsWith(str:String, ending:String):Boolean {
var index:int = str.lastIndexOf(ending)
return index > -1 && index == str.length - ending.length;
}
trace(endsWith("Hello World", "World"))
/yourword$/.test(string) is the regex pattern to test if a string ends with a specific value.
Please read documentation. [http://help.adobe.com/en_US/AS2LCR/Flash_10.0/help.html?content=00001551.html]
searchString.lastIndexOf("TheWord");
I want to compare the first letter of a string with a known character. For example, I want to check if the string "example"'s first letter matches with "e" or not. I'm sure there must be a very simple way to do it, but I could not find it.
One way is to get the first character with string index:
if {[string index $yourstring 0] eq "e"} {
...
I think it's a good idea to collect the different methods in a single answer.
Assume
set mystring example
set mychar e
The goal is to test whether the first character in $mystring is equal to $mychar.
My suggestion was (slightly edited):
if {[string match $mychar* $mystring]} {
...
This invocation does a glob-style match, comparing $mystring to the character $mychar followed by a sequence of zero or more arbitrary characters. Due to shortcuts in the algorithm, the comparison stops after the first character and is quite efficient.
Donal Fellows:
if {[string index $mystring 0] eq $mychar} {
...
This invocation specifically compares a string consisting of the first character in $mystring with the string $mychar. It uses the efficient eq operator rather than the == operator, which is the only one available in older versions of Tcl.
Another way to construct a string consisting of the first character in $mystring is by invoking string range $mystring 0 0.
Mark Kadlec:
if {[string first $mychar $mystring] == 0 }
...
This invocation searches the string $mystring for the first occurrence of the character $mychar. If it finds any, it returns with the index where the character was found. This index number is then compared to 0. If they are equal the first character of $mystring was $mychar.
This solution is rather inefficient in the worst case, where $mystring is long and $mychar does not occur in it. The command will then examine the whole string even though only the first character is of interest.
One more string-based solution:
if {[string compare -length 1 $mychar $mystring] == 0} {
...
This invocation compares the first n characters of both strings (n being hardcoded to 1 here): if there is a difference the command will return -1 or 1 (depending on alphabetical order), and if they are equal 0 will be returned.
Another solution is to use a regular expression match:
if {[regexp -- ^$mychar.* $mystring]} {
...
This solution is similar to the string match solution above, but uses regular expression syntax rather than glob syntax. Don't forget the ^ anchor, otherwise the invocation will return true if $mychar occurs anywhere in $mystring.
Documentation: eq and ==, regexp, string
if { [string first e $yourString] == 0 }
...
set mychar "e"
if { [string first $mychar $myString] == 0}{
....
I have a Groovy method that currently works but is real ugly/hacky looking:
def parseId(String str) {
System.out.println("str: " + str)
int index = href.indexOf("repositoryId")
System.out.println("index: " + index)
int repoIndex = index + 13
System.out.println("repoIndex" + repoIndex)
String repoId = href.substring(repoIndex)
System.out.println("repoId is: " + repoId)
}
When this runs, you might get output like:
str: wsodk3oke30d30kdl4kof94j93jr94f3kd03k043k?planKey=si23j383&repositoryId=31850514
index: 59
repoIndex: 72
repoId is: 31850514
As you can see, I'm simply interested in obtaining the repositoryId value (everything after the = operator) out of the String. Is there a more efficient/Groovier way of doing this or this the only way?
There are a lot of ways to achieve what you want. I'll suggest a simple one using split:
sub = { it.split("repositoryId=")[1] }
str='wsodk3oke30d30kdl4kof94j93jr94f3kd03k043k?planKey=si23j383&repositoryId=31850514'
assert sub(str) == '31850514'
Using a regular expression you could do
def repositoryId = (str =~ "repositoryId=(.*)")[0][1]
The =~ is a regex matcher
or a shortcut regexp - if you are looking only for single match:
String repoId = str.replaceFirst( /.*&repositoryId=(\w+).*/, '$1' )
All the answers here contains regular expressions, however there are a bunch of string methods in Groovy.
String Function
Sample
Description
contains
myStringVar.contains(substring)
Returns true if and only if this string contains the specified sequence of char values
equals
myStringVar.equals(substring)
This is similar to the above but has to be an exact match for the check to return a true value
endsWith
myStringVar.endsWith(suffix)
This method checks the new value contains an ending string
startsWith
myStringVar.startsWith(prefix)
This method checks the new value contains an starting string
equalsIgnoreCase
myStringVar.equalsIgnoreCase(substring)
The same as equals but without case sensitivity
isEmpty
myStringVar.isEmpty()
Checks if myStringVar is populated or not.
matches
myStringVar.matches(substring)
This is the same as equals with the slight difference being that matches takes a regular string as a parameter unlike equals which takes another String object
replace
myStringVar.replace(old,new)
Returns a string resulting from replacing all occurrences of oldChar in this string with newChar
replaceAll
myStringVar.replaceAll(old_regex,new)
Replaces each substring of this string that matches the given regular expression with the given replacement
split
myStringVar.split(regex)
Splits this string around matches of the given regular expression
Source
I want to use curl to view the source of a page and if that source contains a word that matches the string then it will execute a print. How would I do a if $string contains?
In VB it would be like.
dim string1 as string = "1"
If string1.contains("1") Then
Code here...
End If
Something similar to that but in Perl.
If you just need to search for one string within another, use the index function (or rindex if you want to start scanning from the end of the string):
if (index($string, $substring) != -1) {
print "'$string' contains '$substring'\n";
}
To search a string for a pattern match, use the match operator m//:
if ($string =~ m/pattern/) { # the initial m is optional if "/" is the delimiter
print "'$string' matches the pattern\n";
}
if ($string =~ m/something/) {
# Do work
}
Where something is a regular expression.
For case-insensitive string search, use index (or rindex) in combination with fc. This example expands on the answer by Eugene Yarmash:
use feature qw( fc );
my $str = "Abc";
my $substr = "aB";
print "found" if index( fc $str, fc $substr ) != -1;
# Prints: found
print "found" if rindex( fc $str, fc $substr ) != -1;
# Prints: found
$str = "Abc";
$substr = "bA";
print "found" if index( fc $str, fc $substr ) != -1;
# Prints nothing
print "found" if rindex( fc $str, fc $substr ) != -1;
# Prints nothing
Both index and rindex return -1 if the substring is not found.
And fc returns a casefolded version of its string argument, and should be used here instead of the (more familiar) uc or lc. Remember to enable this function, for example with use feature qw( fc );.
DETAILS:
From the fc docs:
Casefolding is the process of mapping strings to a form where case differences are erased; comparing two strings in their casefolded form is effectively a way of asking if two strings are equal, regardless of case.
From the Unicode FAQ:
Q: What is the difference between case mapping and case folding?
A: Case mapping or case conversion is a process whereby strings are
converted to a particular form—uppercase, lowercase, or
titlecase—possibly for display to the user. Case folding is mostly
used for caseless comparison of text, such as identifiers in a
computer program, rather than actual text transformation. Case folding
in Unicode is primarily based on the lowercase mapping, but includes
additional changes to the source text to help make it
language-insensitive and consistent. As a result, case-folded text
should be used solely for internal processing and generally should not
be stored or displayed to the end user.