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Introduction to Perl Basics: Variables, Input/Output, and File Management

This guide provides an overview of fundamental Perl programming concepts, covering variables, input/output handling, and file management techniques. Learn about scalar and array variables, how to perform standard input and output operations, and how to read from and write to files. The guide also explains file status checking and directory operations, making it a comprehensive resource for beginners looking to improve their Perl skills for web programming applications.

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Introduction to Perl Basics: Variables, Input/Output, and File Management

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  1. Basic Input/Output Web Programming

  2. Review: Perl Basics • Perl Variables • Scalar  holds number, character, string • e.g. $var1 = “Mary”; $var2= 1; • Array  holds a list of scalars • e.g. @array1 = (“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”; Web Programming

  3. File Input/Output • Reading from 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 Web Programming

  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 Web Programming

  5. Working with Directories • Open a directory • opendir (IND, $directory); • Read the contents. • @files = readdir (IND); • Close the directory • closedir (IND);  Example script Web Programming

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