CODEWITHSUNDEEP
stringraku
jjmerelo
jjmerelo

Reputation: 23537

print, put, say and escape characters

According to the docs, the only difference between print and say seems to be the fact that the latter adds "\n" (and stringifies using .gist). However, 

perl6 -e 'print "del\b\b"'

prints "d", effectively applying escape characters, while

perl6 -e 'put "del\b\b"'

will output "del" (the same as say). Is it possible that there's a third way of stringifying strings, besides .gist and simple .Str?

As a matter of fact, any character behind the \b will make them behave in the same way. So any idea of why this happens?

Upvotes: 7

Views: 164

Answers (2)

Norman Gaywood
Norman Gaywood

Reputation: 357

To see what's being output, without possible confusion of what the terminal might be doing, you can pipe through xxd (or od)

$ perl6 -e 'say "del\b\b"' | xxd
00000000: 6465 6c08 080a                           del...
$ perl6 -e 'print "del\b\b"' | xxd
00000000: 6465 6c08 08                             del..
$ perl6 -e 'put "del\b\b"' | xxd
00000000: 6465 6c08 080a                           del...

Upvotes: 7

Elizabeth Mattijsen
Elizabeth Mattijsen

Reputation: 26969

FWIW, I see "del" in both cases, regardless of using print or put, so maybe there is some terminal setting that is affecting the behaviour?

The \b\b only become obvious when you actually put characters after them:

say "del\b\bo the right thing"  # do the right thing

\b only moves the cursor back one position. It does not erase anything by itself. If you want the characters erase, you'd have to have them followed by spaces, and then backspace again if you want any text after that again:

print "del\b\b  \b\b"           # d

Upvotes: 10

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