8
String
Manipulation
CGI/Perl
Programming
By Diane Zak
1
8
Objectives
• In this chapter, you will:
• Convert a string to uppercase letters
using the uc function
• Convert a string to lowercase letters
using the lc function
• Return, replace, or insert text using
the substr function
• Use the index function to locate a
string within another string
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8
Objectives
• In this chapter, you will:
• Replace text using the transliteration
operator
• Use the binding operators
• Perform pattern matching using the
matching operator
• Include metacharacters in a search
pattern
• Replace text using the substitution
operator
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8
Introduction
• Often, a script will need to
manipulate data it receives
from a server
– Formatting
– Conversion
– Other tasks
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8
The uc and lc functions
• String comparisons are case
sensitive
• Instead of checking for multiple
cases within a condition
statement, can use functions to
temporarily change the case
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8
The uc and lc functions
• uc function:
– Changes string to all upper case
– Syntax:
• uc (string)
– Example:
if (uc($answer) eq “Y”) {
statement(s) to process
if condition is true
}
Results:
Temporarily
converts the
contents of the
$answer
variable to
uppercase, then
compares the
uppercase
value to “Y” 6
8
The uc and lc functions
• lc function:
– Changes string to all lower case
– Syntax:
• lc (string)
Results:
– Example:
Temporarily
while (lc($item) ne “done”) { converts the
contents of the
statement(s) to process $item variable
to lowercase,
while condition is true
then compares
}
the lowercase
value to “done”
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8
The uc and lc functions
• Both functions only affect alphabetic
characters
• The parentheses around the variable
name is optional
• Can also use ucfirst function
– Converts only first character in string to
uppercase
– Can use with lc to capitalize first letter
of string and have the remaining letters
in lowercase
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8
The substr function
• Can use substr function to:
– Return a portion of a string within
a string
– Replace one or more characters in
a string
– Insert one or more characters
within a string
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8
The substr function
• Using substr to return characters:
– Syntax:
• substr (string, start, length)
– Return length number of characters from string
beginning at start
– If no length, return all characters from start to
end of string
– Examples:
$name = “John Smitty”;
$first = substr ($name, 0, 4);
Assigns John to
$first
$name = “John Smitty”;
$last = substr ($name, 5, 6);
$last = substr ($name, 5);
Both substr
statements assign
Smitty to $last
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8
The substr function
• Using substr to replace characters:
– Syntax:
• substr (string, start, length) = replacementstring
– Replace length number of characters in string with
replacementstring, beginning at start in string
– If no length, replaces all characters from start to
end of string
– Examples:
$name = “Pat Jeffrey”;
Replaces Pat with
substr ($name, 0, 3) = “Patty”; Patty. $name now
stores Patty Jeffrey.
$name = “Pat Jeffrey”;
substr ($name, 4) = “Carr”;
Replaces Jeffrey
with Carr. $name
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now stores Pat Carr.
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The substr function
• Using substr to insert characters:
– Syntax:
• substr (string, start, 0) = insertionstring
– Insert insertionstring within string, beginning
at position start in string.
– Examples:
$price = “45”;
substr ($price, 0, 0) = “\$”;
Inserts a dollar sign in
position 0 of $price
variable, which now
stores $45
$location = “Chicago IL”;
substr ($location, 7, 0) = “, “;
Inserts a comma in
position 7 of $location
variable, which now12
stores Chicago, IL.
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The index function
• Can be used to search a string to
determine if it contains another
string
• Syntax:
– index (string, substring, start)
– Returns the position of the first
occurrence of substring within the
string beginning with start position in
string.
• If substring is not found, function returns –1
• Otherwise, returns the beginning position of
the first occurrence of substring
– If start is omitted, the search begins at
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8
The index function
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The Transliteration and
“Contains” Operators
8
• Transliteration operator:
– Also referred to as the tr operator or the tr///
operator
– Can be used to replace a character in a string
– Syntax:
• string =~ tr/searchlist/replacementlist/modifier
– searchlist – character(s) to search for
– replacementlist – optional. character(s) to replace
character(s) listed in searchlist
– modifier – optional.
»d
»c
»s
Delete found but unreplaced characters
Complement the searchlist
Squash duplicate replaced characters15to a
single character
The Transliteration and
“Contains” Operators
8
• “contains” operator:
– Also referred to as a binding
operator
– Represented by =~
– Used with tr/// operator
• Tells tr/// operator to search string to
determine if it contains any of the
characters in searchlist
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The Transliteration and
“Contains” Operators
8
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The Transliteration and
“Contains” Operators
8
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8
The Match Operator
• Can be used to determine if a
string is contained within
another string
– Like the index function
– Referred to as the m operator or
the m/// operator
– Can use the “contains” operator
(=~) or the “does not contain”
operator (!~)
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The Match Operator
8
20
Using Metacharacters
in a Search Pattern
8
21
Using Metacharacters
in a Search Pattern
8
22
Using Metacharacters
in a Search Pattern
8
• Metacharacters and the m///
operator can be used to verify
an email address:
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The Substitution
Operator
8
• Can be used to:
– Replace one or more characters in
a string
– Remove one or more characters
from a string
– Also referred to as the s operator
or the s/// operator
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The Substitution
Operator
8
25
8
The International
Coffees Form and Script
26
8
The International
Coffees Form and Script
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8
Summary
• The uc function temporarily converts the
letters in a string to uppercase.
• The lc function temporarily converts the
letters in a string to lowercase.
• You can use the substr function to:
– Return portion of a string contained in another string
– Replace character(s) in a string
– Insert character(s) into a string
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Summary
8
• The index function to determine if string
contains substring
– Returns position number of beginning of substring
If substring is not within string, returns –1
• The tr/// (transliteration) operator can
replace a character in a string, or delete a
character from a string.
• The m// (match) operator can determine if a
string is contained in another string.
– Returns true or false
– If assigned to an array, returns list of values that
match searchpattern
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8
Summary
• The searchpattern entered in the m// and
s/// operators can include
metacharacters:
–
–
–
–
Match
Match
Match
Match
single character(s)
whitespace character(s)
boundary character(s)
repeated characters
• The s/// (substitution) operator can be
used to replace or delete character(s) in
a string.
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