Shell Programming and Scripting

#!/usr/bin/perl -w

print " Welcome to advance search function";

$func = "";

while (( $func ne "quit\n" ) && ( $func2 = "exit\n" ))
{
    print " Enter advance search function :";
    $func = <STDIN>; $func2 = <STDIN>;
    
    
}
print " return to main menu \n";

$
$
$ # list the name and sizes of all text files in the current directory
$
$ wc *.txt
 0  0  0 a.txt
 1  1  3 b.txt
 1  1  5 c.txt
 1 11 51 d.txt
 3 13 59 total
$
$
$ # display the contents of the Perl program
$
$ cat -n search.pl
     1  #perl -w
     2  print "Enter expression: ";                              # prompt for user input
     3  chomp ($input = <STDIN>);                                # assign input to $input
     4  while ($input ne "quit") {                               # loop until user enters "quit"
     5    print "Expression to test: Filesize $input\n";         # print message
     6    print "It is TRUE for the following files:\n\n";       # print message
     7    foreach $file (glob "*.txt") {                         # loop through all text files in current dir
     8      $size = -s $file;                                    # find out the size of current file in loop
     9      $expr = "-s \"$file\" $input";                       # cook up the expression for testing filesize
    10      $output = eval $expr;                                # evaluate the expression
    11      die "Oops, something went wrong: $@" if $@;          # halt the program if something went wrong
    12      if ($output) {                                       # otherwise
    13        print "File Name = $file; File size = $size\n";    # print the file name if the expression
    14      }                                                    # could be evaluated successfully
    15    }                                                      # finish looping through all files
    16    print "\nEnter expression: ";                          # so prompt the user again
    17    chomp ($input = <STDIN>);                              # and set the input to $input
    18  }
$
$
$ # Now run the Perl program
$
$ perl search.pl
Enter expression: < 5
Expression to test: Filesize < 5
It is TRUE for the following files:

File Name = a.txt; File size = 0
File Name = b.txt; File size = 3

Enter expression: >= 0
Expression to test: Filesize >= 0
It is TRUE for the following files:

File Name = a.txt; File size = 0
File Name = b.txt; File size = 3
File Name = c.txt; File size = 5
File Name = d.txt; File size = 51

Enter expression: > 0
Expression to test: Filesize > 0
It is TRUE for the following files:

File Name = b.txt; File size = 3
File Name = c.txt; File size = 5
File Name = d.txt; File size = 51

Enter expression: != 5
Expression to test: Filesize != 5
It is TRUE for the following files:

File Name = a.txt; File size = 0
File Name = b.txt; File size = 3
File Name = d.txt; File size = 51

Enter expression: < 0
Expression to test: Filesize < 0
It is TRUE for the following files:


Enter expression: > 1000
Expression to test: Filesize > 1000
It is TRUE for the following files:


Enter expression: quit
$
$ # Another trial run
$
$ perl search.pl
Enter expression: < 50
Expression to test: Filesize < 50
It is TRUE for the following files:

File Name = a.txt; File size = 0
File Name = b.txt; File size = 3
File Name = c.txt; File size = 5

Enter expression: blah
Expression to test: Filesize blah
It is TRUE for the following files:

Bareword found where operator expected at (eval 10) line 1, near ""a.txt" blah"
        (Missing operator before blah?)
Oops, something went wrong: syntax error at (eval 10) line 2, near ""a.txt" blah
"
$
$
$