Ruby Text — Learning Library

02 — Reading and writing

Ruby Text — Learning Library

Ruby text — a learning library
Start Here
Start Here
Strings Carry an Encoding
Strings Carry an Encoding
- A string is bytes plus a label
  A string is bytes plus a label
- Mixing encodings raises — unless it is all ASCII
  Mixing encodings raises — unless it is all ASCII
- Invalid bytes get in, and fail later
  Invalid bytes get in, and fail later
- String.new is binary; "" is not
  String.new is binary; "" is not
Reading and Writing
Reading and Writing
- What File.read returns depends on the locale
  What File.read returns depends on the locale
- The BOM is kept unless you ask
  The BOM is kept unless you ask
- chomp knows about CRLF
  chomp knows about CRLF
Unicode
Unicode
- length counts code points
  length counts code points
- Normalization is built in
  Normalization is built in
- Case mapping is full Unicode, with options instead of a locale
  Case mapping is full Unicode, with options instead of a locale
Regex
Regex
- ^ and $ match at every line
  ^ and $ match at every line
- \w is ASCII, [[:alpha:]] is not, and \b sides with Unicode
  \w is ASCII, [[:alpha:]] is not, and \b sides with Unicode
- \h is a hex digit in Ruby and a blank in Perl
  \h is a hex digit in Ruby and a blank in Perl
- Named captures become local variables — sometimes
  Named captures become local variables — sometimes
- Backtracking has a cache, and a timeout
  Backtracking has a cache, and a timeout
Literals
Literals
- String literals are chilled, not frozen
  String literals are chilled, not frozen
- <<~ strips indentation — by a different rule than Perl's
  <<~ strips indentation — by a different rule than Perl's
Perl Heritage
Perl Heritage
- ruby -n -p -a -F -l -i came from Perl
  ruby -n -p -a -F -l -i came from Perl
- split has an awk mode
  split has an awk mode
- succ counts in letters
  succ counts in letters
- pack and unpack speak Perl's template language
  pack and unpack speak Perl's template language
Parsing and Formatting
Parsing and Formatting
- to_i never fails; Integer() does
  to_i never fails; Integer() does
- ljust and %-8s pad by code points, not columns
  ljust and %-8s pad by code points, not columns
Resources
Resources

02 — Reading and writing¶

A string read from outside the program gets its encoding label from somewhere other than your code. This chapter is about where from — and about two things at the edges of a file that the label does not explain: a byte order mark at the start, and a \r at the end of every line.

Lesson	The one thing
What `File.read` returns depends on the locale	US-ASCII under `LC_ALL=C`, and what `-E` does and does not fix
The BOM is kept unless you ask	`BOM\\|UTF-8`, and the CSV header that is not `"id"`
`chomp` knows about CRLF	where Ruby parted from Perl, and where `lines` did not