1. Basic Input/Output
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2. Review: Perl Basics Perl Variables Standard Input Standard Output
Scalar  holds number, character, string
e.g. $var1 = “Mary”; $var2= 1;
Array  holds a list of scalars
= (“Mary”,”Tom”);
Standard Input
<STDIN>  reads 1 line from standard input
e.g., $line= <STDIN>;
Standard Output
print  writes to standard output
e.g., print “My name is $name\n”;
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3. File Input/Output Reading from a file Writing to a file
open (INF,”$file1”); # open $file1 for reading
$line = <INF>; # read in one line
Writing to a file
open (OUTF, “>$file2”); # open $file2 for writing
open (OUTF, “>>$file2”); # open $file2 for appending
print OUTF “This is line1\n”; # print to $file2
Closing a file after reading/writing
close (FILE);
Terminating program for bad file I/O
open (FILE,$file) || die “can’t read $file”;
 Example script
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4. Determining File Status
Syntax
if ( -test $file ) { statements }
File test operators
-d : Is $file a directory?
-e : Does $file exist?
-f : Is $file is an ordinary file?
-l : Is $file a symbolic link?
-s : Is $file a non-empty file?
-z : Is $file an empty file?
-r/-w/-x : Is $file readable/writable/executable?
 Example script
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5. Working with Directories
Open a directory
opendir (IND, $directory);
Read the contents.
@files = readdir (IND);
Close the directory
closedir (IND);
 Example script
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