[perl] Wide character in say at F:\rename.pl line 17. tell me how to suppress this message

 

Ah, the classic Perl "Wide character in print" warning. That's a bit of a "lost in translation" moment between Perl and your terminal.

This happens because Perl’s say (or print) is trying to output a string containing characters that require more than one byte (like that em dash or Unicode characters), but the output handle (usually STDOUT) is still expecting old-school, single-byte data.

Here are the best ways to handle this, depending on how "correct" you want to be.

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1. The "Proper" Way (Global Fix)

The cleanest solution is to tell Perl that your output should always use UTF-8. Add this line near the top of your script:

Perl

 

use open qw(:std :utf8);

This automatically applies UTF-8 encoding to STDOUT, STDERR, and STDIN. It’s the "set it and forget it" approach for modern scripts.

2. The Targeted Way (Handle Specific)

If you only want to fix it for standard output without affecting how you read files, use binmode:

Perl

 

binmode(STDOUT, ":utf8");

Put this before your say command on line 17. It tells Perl: "Hey, when you send data to the screen, treat it as UTF-8."

3. The "Quick & Dirty" Way (One-Liner)

If you are running the script from the command line and don't want to edit the code, you can use the -C flag to enable Unicode features:

Bash

 

perl -C -S rename.pl

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Why is Perl complaining?

Perl treats strings as sequences of characters, but the outside world (your files and terminal) sees them as sequences of bytes.

When you have a "wide" character (anything with a code point above 255), Perl doesn't know how to "shrink" that character into a single byte for your terminal, so it prints the warning and just shoves the raw bits through. By using the methods above, you’re giving Perl a "map" (the UTF-8 layer) to translate those characters correctly.

 

 

 

 

 

In typography and digital character encoding, the "wide" dash you’re looking at is called an em dash. It’s considered a wide character because its design is historically and mathematically tied to the square of the current font size.

  

Here is the breakdown of why it exists and why it’s sized the way it is:

1. The "Em" Measurement

The name "em dash" comes from the world of physical typesetting. An em is a unit of measurement equal to the point size of the font.

 

 

• If you are typing in a 12pt font, an em dash is roughly 12 points wide.

   

   

• It was originally named because, in many early typefaces, the uppercase letter "M" was cast on a square block, making it exactly as wide as the font height.

   

   

2. The Purpose of Width

The em dash is intentionally wide to provide a strong visual break in a sentence. While a hyphen (-) joins words and an en dash (–) shows ranges, the em dash acts like a "super-comma" or a pair of parentheses.

 

 

Its width ensures that the reader's eye registers a significant pause or a shift in thought, preventing it from being confused with shorter punctuation marks.

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Comparison of Horizontal Bars

Character	Name	Width Context	Common Use
-	Hyphen	Very Narrow	Joining words (e.g., "well-being")
–	En Dash	Width of an "n"	Ranges (e.g., "1990–2000")
—	Em Dash	Width of an "m"	Interrupting a thought

3. Digital Encoding

In the digital world (Unicode), the em dash is assigned its own unique code point (U+2014). Because it is defined as a distinct character from the hyphen, your computer knows to render it using the specific, wider "glyph" designed by the font creator.

 

 

Fun Fact: In the days of typewriters, there was no em dash key. People started using two hyphens (--) to mimic the width of an em dash, a habit that many people (and some auto-correct software) still use today!

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Would you like me to show you the keyboard shortcuts for creating an em dash on your specific operating system?