Perl Tutorials - Herong's Tutorial Examples - v6.01, by Dr. Herong Yang
open() - Opening File Handles for Input and Output
This section describes various ways to use the open() function to open file handles to input data from files or output data to files, input data from another process or output data to another process.
Input to and output from Perl programs must be done through file handles. File handles are created by calling the open() function in different ways for different situations. Examples are:
1. Open a file handle for input from the file named by an expression:
rc = open(file_handle, expression);
2. Open a file handle for input from the file named by an expression:
rc = open(file_handle, "< ".expression);
3. Open a file handle for output to the file named by an expression:
rc = open(file_handle, "> ".expression);
4. Open a file handle for output to append to the file named by an expression:
rc = open(file_handle, ">> ".expression);
5. Open a file handle for output to and input from the file named by an expression:
rc = open(file_handle, "+> ".expression);
I am not sure how input and output can be managed on the same file. Need to be tested.
6. Open a file handle for input from another process named by an expression:
rc = open(file_handle, expression." |");
In this case, "rc" is the process id forked by this call.
7. Open a file handle for output to another process named by an expression:
rc = open(file_handle, "| ".expression);
In this case, "rc" is the process id forked by this call.
8. Open a file handle for input from the standard input channel, usually the key board:
rc = open(file_handle, "_");
9. Open a file handle for output to the standard output channel, usually the monitor screen:
rc = open(file_handle, ">_");
10. Open a file handle for input from a file named by the scale variable of the same name as the file handle:
rc = open(file_handle);
The above statement is equivalent to rc=open(file_handle,$file_handle).
There are 3 pre-defined file handles:
File handles are closed by the close function:
rc = close(file_handle);
Table of Contents
Data Types: Values and Variables
Expressions, Operations and Simple Statements
Name Spaces and Perl Module Files
Hard References - Addresses of Memory Objects
Objects (or References) and Classes (or Packages)
Typeglob and Importing Identifiers from Other Packages
String Built-in Functions and Performance
►File Handles and Data Input/Output
►open() - Opening File Handles for Input and Output
print() - Printing Output to File Handles
<file_handle> - Reading Data from File Handles
Open Directories and Read File Names
File System Functions and Operations
Socket Communication Over the Internet
XML::Simple Module - XML Parser and Generator
SOAP::Lite - SOAP Server-Client Communication Module
Perl Programs as IIS Server CGI Scripts
CGI (Common Gateway Interface)
XML-RPC - Remote Procedure Call with XML and HTTP
RPC::XML - Perl Implementation of XML-RPC
Integrating Perl with Apache Web Server
CGI.pm Module for Building Web Pages
LWP::UserAgent and Web Site Testing
Converting Perl Script to Executable Binary