perl syntax help

Shell Programming and Scripting
1

Im new at scripting and im trying to write a script using perl that will make sure there are 2 command line integer arguments and then check if the 2nd argument is greater than the first. i believe im close but still receive my error message even when i have 2 arguments and the second part gives me an error about an useless array

these are the errors im receiving
/export/home/sieben01/itec400/homework> ./intlist.pl 1 2
Useless use of array element in void context at ./intlist.pl line 19.
error: incorect number of arguments
usage: intlist.pl a b (where a < b)

unless ($#ARGV==2){
print "error: incorect number of arguments",
"\n",
"usage: intlist.pl a b (where a < b)",
"\n";
exit 1
}

if ($ARGV[1] => $ARGV[2]){
print "error: first argument must be less than the second asrgument",
"\n",
"Useage: intlist.pl a b (Where a < b)",
"\n";
exit 1
}
2

$#array gives you the index of the last element of the array. Since numbering starts at 0 (as in most computing languages), a 2 element array will return 1. An alternative would be using the scalar function.

$ cat args.pl
print '      $#ARGV: ', $#ARGV, "\n";
print 'scalar @ARGV: ', scalar @ARGV, "\n";
$ perl args.pl 1 2
      $#ARGV: 1
scalar @ARGV: 2
$ perl args.pl 1 2 3
      $#ARGV: 2
scalar @ARGV: 3
3

seems easier but im doing this for a class and were supposed to use arrays.

heres what i have now. :frowning: i dont understand it really. any help?

unless ($#ARGV==2){
print "error: incorect number of arguments",
"\n",
"usage: intlist.pl a b (where a < b)",
"\n";
exit 1;
}

if ($ARGV[1] => $ARGV[2]){
print "error: first argument must be less than the second argument",
"\n",
"Usage: intlist.pl a b (Where a < b)",
"\n";
exit 1;
}
else {
$COUNTER=$ARGV[1];
while($COUNTER <=$ARGV[2]){
print $COUNTER;
if ($COUNTER <= $ARGV[2]0{
print ",";
}
else {
print "\n";
4

What should this script do if a < b ?

5

its supposed to accept exactly 2 integer arguments where the first argument must be less than the second argument. The script will print a comma separated list of integers starting with the first argument up through the second argument.

6 
#!/usr/bin/perl

use strict;
use warnings;

my @array;

if (@ARGV != 2){
print "error: incorect number of arguments",
"\n",
"usage: intlist.pl a b (where a < b)",
"\n";
exit 1;
}

if ($ARGV[0] >= $ARGV[1]){
print "error: first argument must be less than the second argument",
"\n",
"Usage: intlist.pl a b (Where a < b)",
"\n";
exit 1;
}

foreach my $argnum ($ARGV[0] .. $ARGV[1]) {
push @array, "$argnum";
push @array, ",";
}

pop(@array);

print @array;
print "\n";

---------- Post updated at 20:59 ---------- Previous update was at 20:53 ----------

Test run:

$ ./intlist.pl
error: incorect number of arguments
usage: intlist.pl a b (where a < b)
$ 
$ ./intlist.pl 20 10
error: first argument must be less than the second argument
Usage: intlist.pl a b (Where a < b)
$ 
$ ./intlist.pl 10 10
error: first argument must be less than the second argument
Usage: intlist.pl a b (Where a < b)
$ 
$ ./intlist.pl 10 20
10,11,12,13,14,15,16,17,18,19,20
$
7

thank you