Compilers-What is the difference between: 'String literal' and 'Any String' in this exercise?

Question

The dragon book, exercise 3.3.10 The UNIX shell command .sh uses the operators in fig 3.9 in filenames expressions to define sets of file names. For example, the file name expression *.o matches all file names ending in .o; sort1.? matches all file names of sort.c, where c is any character. Show how sh filenames expressions can be replaced by equivalent regular expressions using only basic union, concatenation and closure operation

So what is the difference between string literall and any string? I though String literal was anything like s = "blabla" with the /n in the last position. It also comes to the character, what it actually meant when said character c literally and any character.

`'abc'` will match only the filename `abc`. `ab?` matches `abc`, `abd`, `abe`, and so on. `'ab?'` and `ab\?` both matches `ab?` only. — Colonel Thirty Two, Sep 11 '15 at 00:58

score 0 · Answer 1 · answered Sep 11 '15 at 03:38

0

You may be overthinking this, but it's mostly self explanatory. Literally means exactly that. So "s" means _exactly the string s.

Contrast this with any string, *. This means that it could be s, but it could also be a, ss, whatever string you want, or nothing at all.

Any character or ? can be any single character like a, s, or c, but not ss because that is more than one character.

answered Sep 11 '15 at 03:38

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But what would s be? you mean s is a string like: string s = "s", LITERALLY s? if it is then could you explain me the example they used? thank you – Bruno Braga Sep 11 '15 at 03:58
Yes `'s'` is like `string s = "s"`. Their example is a literal backslash, `\\`. – Explosion Pills Sep 11 '15 at 04:09

Compilers-What is the difference between: 'String literal' and 'Any String' in this exercise?

1 Answers1