Syntax:
The syntax of the “shift” function is given as follows:
shift
Or
shift ARRAY
Different Uses of the “Shift” Function
Different ways of using the “shift” function to read the argument values and array values are shown in this part of the tutorial.
Example 1: Use of the “Shift” Function to Read the Command Line Arguments
The command line argument values can be read using the “shift” command without any argument. The @ARGV array is used to store the command line argument values. In the following script, the total number of the command line argument values is counted using the $#ARGV variable. Next, the “for” loop is used to read all the argument values using the “shift” function without any argument.
use strict;
use warnings;
#Declare a variable to store the argument value
my $var;
#Count the total number of arguments
my $total_arguments = $#ARGV + 1;
#Print the total number of arguments
print "Total arguments: $total_arguments\n";
#Read and print the argument values
for(my $i = 1; $i <= $total_arguments; $i++)
{
#read the argument
$var = shift;
#print the argument
print "Argument $i: $var\n";
}
Output:
According to the following output, 67, 34, and 23 are given as the argument values during the execution of the script which is printed as follows:
Example 2: Use of the “Shift” Function to Read the Function Arguments
In this example, an array of five string values is declared and this array is passed as the argument of the subroutine named read_func(). The “shift” function without an argument is used inside the function to read the first element of the array. The array values are printed before and after calling the function.
use strict;
use warnings;
#Declare an array of string
my @os = ('Ubuntu', 'CentOS', 'Kubuntu', 'Fedora', 'RedHat');
print "The array values before calling the function: \n @os\n";
#Call the function by passing the array as an argument
read_func(@os);
print "\nThe array values after calling the function: \n @os\n";
#Declare the function that will shift one array value
sub read_func {
my $element = shift;
print "\nThe retrieved value is $element.\n";
}
Output:
The following output appears after executing the script. According to this output, the “shift” function just read the first element of the array but didn’t remove the element from the array:
Example 3: Use of the “Shift” Function with an Array
In this example, the “shift” function is used with an array that removes the first element of the array. An array of five elements is declared in the script. The “shift” function is executed with the array as an argument. The array values are printed before and after calling the “shift” function.
#Declare an array of string
my @os = ('Ubuntu', 'CentOS', 'Kubuntu', 'Fedora', 'RedHat');
#Print array before the shift
print "The array values before calling the shift function: \n @os\n";
#Remove the first element from the left side of the array
my $element = shift(@os);
print "\n$element is removed from the array.\n";
#Print array after shift
print "\nThe array values after calling the shift function: \n @os\n";
Output:
The following output appears after executing the script. According to this output, the “shift” function removed the first element from the array:
Example 4: Use of the “Shift” Function in the Loop
In this example, the “shift” function is used with a “while” loop to read the array value by removing the value from the array in each iteration of the loop. An array of five numbers is defined in the script. The array values are printed before and after executing the loop.
use strict;
use warnings;
#Declare a numeric array
my @num_arr = (90, 23, 78, 19, 56);
#Print the array values
print "Array values before shift: \n@num_arr\n";
print "The shifted array values:\n";
#shift each element of the array using the loop
while (my $value = shift(@num_arr)) {
print("$value ");
}
print "\nArray values after shifting :\n";
#Check the total number of elements after the shift
if($#num_arr < 0)
{
print "The array is empty.\n";
}
else
{
print "@num_arr\n";
}
Output:
The following output appears after executing the script. According to this output, the “shift” function removed all elements from the array after executing the block of the “while” loop:
Conclusion
The uses of the “shift” function to read the command line argument values, function argument, and array values are shown in this tutorial.
