! Aware to Perl: How come when I open the file read-write it wipes it out?

How come when I open the file read-write it wipes it out?

Tips: Browse or Search all pages for efficient awareness of Perl functions, operators, and FAQs.

Subjects

By activity
Professions, Sciences, Humanities, Business, ...

User Interface
Text-based, GUI, Audio, Video, Keyboards, Mouse, Images,...

Text Strings
Conversions, tests, processing, manipulation,...

Math
Integer, Floating point, Matrix, Statistics, Boolean, ...

Processing
Algorithms, Memory, Process control, Debugging, ...

Stored Data
Data storage, Integrity, Encryption, Compression, ...

Communications
Networks, protocols, Interprocess, Remote, Client Server, ...

Hard World
Timing, Calendar and Clock, Audio, Video, Printer, Controls...

File System
Management, Filtering, File & Directory access, Viewers, ...

Because you're using something like this, which truncates the file and then gives you read-write access:

    open(FH, "+> /path/name");  # WRONG

Whoops. You should instead use this, which will fail if the file doesn't exist.

    open(FH, "+< /path/name");  # open for update

If this is an issue, try:

    sysopen(FH, "/path/name", O_RDWR|O_CREAT, 0644);

Error checking is left as an exercise for the reader.

Source: Perl FAQ: Files and Formats
Copyright: Copyright (c) 1997 Tom Christiansen and Nathan Torkington.

(Corrections, notes, and links courtesy of RocketAware.com)

[Overview Topics]

Up to: File Access

Rapid-Links: Search | About | Comments | Submit Path: RocketAware > Perl > perlfaq5/How_come_when_I_open_the_file_re.htm