string starts with ...

string starts with ...

[Matthias Berndt]

Greetings,

how can I test if a string starts with '#'?
I can't find the trick.

Thanks
	Matthias

Re: string starts with ...

[Hannu Koivisto]

Matthias Berndt <berndt.matthias@gmx.de> writes:

> how can I test if a string starts with '#'?
> I can't find the trick.

[[ $YOURSTRING == \#* ]]

See "Conditional Expressions" in the manual.

-- 
Hannu

Re: string starts with ...

[Bart Schaefer]

On Jan 21,  4:05pm, Hannu Koivisto wrote:
} Subject: Re: string starts with ...
}
} Matthias Berndt <berndt.matthias@gmx.de> writes:
} 
} > how can I test if a string starts with '#'?
} 
} [[ $YOURSTRING == \#* ]]
} 
} See "Conditional Expressions" in the manual.

I think the problem isn't understanding of conditional expressions, it's
that '#' normally starts a comment, so you have to quote it.

} > I can't find the trick.

The "trick" is to quote ONLY the '#' character and not the rest of the
pattern.  Hence Hannu's solution is the most concise, but these work:

	[[ $YOURSTRING == '#'* ]]

	[[ $YOURSTRING == "#"* ]]

String concatenation in shell language is by simple juxtaposition, no
operator required.

This works, too, by forcing the '#' to be treated as part of a pattern:

	[[ $YOURSTRING == (#)* ]]

Re: string starts with ...

[Peter Stephenson]

Bart Schaefer wrote:
> This works, too, by forcing the '#' to be treated as part of a pattern:
> 
> 	[[ $YOURSTRING == (#)* ]]

You mean with extendedglob turned off.

I tried it with extendedglob turned on (this is for aficionados only):

% [[ 'foo' = (#)foo ]] && echo yes
yes

It looks like it's valid to have zero globbing flags.  The manual
doesn't actually say this in as many words, but it's sort of useful:

% typeset approx
% [[ foo = (#$approx)fo ]] && echo yes
% approx=a1
% [[ foo = (#$approx)fo ]] && echo yes
yes

Note no globsubst trickery needed:  $approx can be a straight string as
long as the # is unquoted.  This probably needs documenting.  However,
I think all globbing flags can be turned off by other flags, so having
none isn't actually that useful.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070


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