Literal mode for string match

[ajeetdsouza]

I think starts-with and ends-with should be a standard inclusion in a set of string processing functions. Currently, I can use matches but I have to do a regex escape on the start of the string, and it unnecessarily complicates what would otherwise be a very simple piece of code.

[floam]

How is string match '*foo' or string match 'foo*' so complicated?

[ajeetdsouza]

How would you find if $str1 starts-with $str2? You can't simply say string match "$str2*" $str1, because $str2 might have special characters like * which would be interpreted differently.

[faho]

That sounds like a case for a "literal" mode for string match, and you'd then have it do substring matching, prefix matching or suffix matching.

[ajeetdsouza]

Could you elaborate on what that might look like?

[faho]

Something like

string match --literal foo foobar # checks if "foo" is anywhere in "foobar"
string match --literal --prefix foo foobar # checks if "foobar" starts with "foo"
string match --literal --suffix foo foobar # checks if it ends with "foo"

or similar. In essence just like you would do --regex mode, but now it's "literal mode".

That way the rest of the string match machinery is there - you can do --quiet to only return a status code, or --invert to return strings that don't fit, or --ignore-case to do a case-insensitive match.

[floam]

How would you find if $str1 starts-with $str2?

string match 'foo*' foobar
or

set str1 foobar 
set str2 foo
string match "$str2*" $str1

Oh I see what you're saying, if str2 actually already had glob characters in it, there is a problem. I was slow on the uptake there.

[vergenzt]

This is similar to how grep has glob mode (the default), --extended-regexp mode (similar to -r) here, and --fixed-strings mode (turn off globbing like in this request).

I wonder if -f/--fixed-string might be an appropriate option name?