input foo, output '[F|f][O|o][O|o]'?

input foo, output '[F|f][O|o][O|o]'?

[TJ Luoma]

Before I reinvent the wheel, I thought I'd ask if someone already had 
(or knew of) a way to take a string of characters and output a 'case 
insensitive' regex version.

For example, if I input 'CrashPlan' I'd want to get out 
[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]

(Input will usually be ASCII letters, with an occasional number and 
perhaps the occasional '-' or '_' but doesn't need to handle anything 
more complex than that.)

I tried Google but found it pretty impossible to make a good query for 
something like this.

TjL

Re: input foo, output '[F|f][O|o][O|o]'?

[ZyX]

I do not think you will find a way to do this. All regex engines (precisely, programs that are using them) I know support a way to set case sensitivity for the whole regular expression and some support toggling this for a part of regular expression. In grep this is an -i switch, for vim it is either /i or \c/\C, for sed this is /i, for PCRE and perl this is additionally (?i) "atom" (additionally to other ways of toggling the behavior which are highly dependent on programs embedding PCRE; for perl this is usual /i flag). Even zsh globs do support (#i).

By the way, what regex engine is your output for? Any I am aware of parse "[N|n]" as "either one of three characters: N, n, or pipe".

I am also assuming XY problem here: what for do you need such conversion? You should consider lowercasing the tested string if nothing like -i is available.

01.07.13, 22:12, "TJ Luoma" <luomat@gmail.com>":
> 
> 
> Before I reinvent the wheel, I thought I'd ask if someone already had 
> (or knew of) a way to take a string of characters and output a 'case 
> insensitive' regex version.
> 
> For example, if I input 'CrashPlan' I'd want to get out 
> [C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]
> 
> (Input will usually be ASCII letters, with an occasional number and 
> perhaps the occasional '-' or '_' but doesn't need to handle anything 
> more complex than that.)
> 
> I tried Google but found it pretty impossible to make a good query for 
> something like this.
> 
> TjL

Re: input foo, output '[F|f][O|o][O|o]'?

[Phil Pennock]

On 2013-07-01 at 13:59 -0400, TJ Luoma wrote:
> Before I reinvent the wheel, I thought I'd ask if someone already had 
> (or knew of) a way to take a string of characters and output a 'case 
> insensitive' regex version.
> 
> For example, if I input 'CrashPlan' I'd want to get out 
> [C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]

% foo=CrashPlan
% for c in ${(s::)foo}; do print -n "[${(U)c}|${(L)c}]";done; print
[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]
%

If this is for use within zsh, then as ZyX suggests it's simpler, even
for regexp cases:

 setopt rematch_pcre
 [[ "cRAShpLAn" =~ (?i)$foo ]]

-Phil

Re: input foo, output '[F|f][O|o][O|o]'?

[Alex Satrapa]

Since the topic is Regular Expressions, I will take the opportunity to recommend the O'Reilly book, "Mastering Regular Expressions" by Jeffrey Freidl. Even if you only work through the first few chapters (it provides examples for you to play with and learn), it will be worth the investment.

I am a very happy "student" (disciple, even) of Jeffrey Freidl's writing, and I have many O'Reilly books in my library.

Alex Satrapa

On 02/07/2013, at 3:59, "TJ Luoma" <luomat@gmail.com> wrote:

> 
> Before I reinvent the wheel, I thought I'd ask if someone already had (or knew of) a way to take a string of characters and output a 'case insensitive' regex version.
> 
> For example, if I input 'CrashPlan' I'd want to get out [C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]
> 
> (Input will usually be ASCII letters, with an occasional number and perhaps the occasional '-' or '_' but doesn't need to handle anything more complex than that.)
> 
> I tried Google but found it pretty impossible to make a good query for something like this.
> 
> TjL

Re: input foo, output '[F|f][O|o][O|o]'?

[TJ Luoma]

On 1 Jul 2013, at 15:37, Phil Pennock wrote:

> % foo=CrashPlan
> % for c in ${(s::)foo}; do print -n "[${(U)c}|${(L)c}]";done; print
> [C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]
> %

That works great.

Thanks!


> If this is for use within zsh, then as ZyX suggests it's simpler, even
> for regexp cases:
>
> setopt rematch_pcre
> [[ "cRAShpLAn" =~ (?i)$foo ]]

It isn't… but that's helpful for future reference.

TjL

Re: input foo, output '[F|f][O|o][O|o]'?

[Kurtis Rader]

[-- Attachment #1: Type: text/plain, Size: 1829 bytes --]

+1 Alex's recommendation. The optimal answer depends on the capabilities of
the regex engine you're targeting. In zsh, for example, you can use the #i
modifier to make globs case insensitive. There's also the zsh/pcre module
which provides Perl compatible regex support including case insensitive
matches. In short, for any reasonable regex implementation there is no need
to resort to something as clumsy  as what you propose. Keep in mind to that
for anything other than ASCII this is impossible, for all practical
purposes, to implement correctly using the strategy you had in mind.


On Mon, Jul 1, 2013 at 4:51 PM, Alex Satrapa <grail@goldweb.com.au> wrote:

> Since the topic is Regular Expressions, I will take the opportunity to
> recommend the O'Reilly book, "Mastering Regular Expressions" by Jeffrey
> Freidl. Even if you only work through the first few chapters (it provides
> examples for you to play with and learn), it will be worth the investment.
>
> I am a very happy "student" (disciple, even) of Jeffrey Freidl's writing,
> and I have many O'Reilly books in my library.
>
> Alex Satrapa
>
> On 02/07/2013, at 3:59, "TJ Luoma" <luomat@gmail.com> wrote:
>
> >
> > Before I reinvent the wheel, I thought I'd ask if someone already had
> (or knew of) a way to take a string of characters and output a 'case
> insensitive' regex version.
> >
> > For example, if I input 'CrashPlan' I'd want to get out
> [C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]
> >
> > (Input will usually be ASCII letters, with an occasional number and
> perhaps the occasional '-' or '_' but doesn't need to handle anything more
> complex than that.)
> >
> > I tried Google but found it pretty impossible to make a good query for
> something like this.
> >
> > TjL
>



-- 
Kurtis Rader
Caretake of the exceptional canines Junior and Chino

Re: input foo, output '[F|f][O|o][O|o]'?

[TJ Luoma]

On 1 Jul 2013, at 14:44, ZyX wrote:

> I do not think you will find a way to do this. All regex engines 
> (precisely, programs that are using them) I know support a way to set 
> case sensitivity for the whole regular expression and some support 
> toggling this for a part of regular expression. In grep this is an -i 
> switch, for vim it is either /i or \c/\C, for sed this is /i, for PCRE 
> and perl this is additionally (?i) "atom" (additionally to other ways 
> of toggling the behavior which are highly dependent on programs 
> embedding PCRE; for perl this is usual /i flag). Even zsh globs do 
> support (#i).

Phil Pennock's version worked great:

% foo=CrashPlan
% for c in ${(s::)foo}; do print -n "[${(U)c}|${(L)c}]";done; print
[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]
%


> By the way, what regex engine is your output for? Any I am aware of 
> parse "[N|n]" as "either one of three characters: N, n, or pipe".

Really? I can think of several that support it. Maybe it's because I'm 
old enough to remember when a lot of these utilities didn't have 'ignore 
case'

% echo "foo\nbar\nbat" | egrep -v '[F|f]'
bar
bat

% echo "foo\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
XXX
bar
bat

You can also use it for matching case/esac :

case "$i" in
	[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n])
			echo "matched crashplan"
	;;

	*)
			echo "No Match"
	;;

esac


> I am also assuming XY problem here: what for do you need such 
> conversion? You should consider lowercasing the tested string if 
> nothing like -i is available.

It's for use with the AddDescription directive for .htaccess which (from 
what I understand) takes its case sensitivity from the underlying 
filesystem when matching filenames. There's no "ignore case" flag or 
anything else that I can use with it, so my only option (at least, the 
only one I can think of) is the one that I suggested. For example, if I 
wanted to add this for any files which start with 'BBEdit' (case 
insensitive) this is what I'd need to use:

	AddDescription "<a href='http://barebones.com/bbedit'>A text editor 
that doesn't suck</a>" [B|b][B|b][E|e][D|d][I|i][T|t]*

I verified that it works, but typing that stuff manually is tedious and 
highly error prone, which made it the perfect place for a shell script 
:-)

TjL

Re: input foo, output '[F|f][O|o][O|o]'?

[TJ Luoma]

On 1 Jul 2013, at 20:38, Kurtis Rader wrote:

> In short, for any reasonable regex implementation there is no need to 
> resort to something as clumsy  as what you propose.

You would certainly be correct in the vast majority of cases. However, I 
happen to be dealing with one of the small percentages of exceptions, as 
the AddDescription implementation in Apache does not have a 'reasonable 
regex' implementation for this, as far as I have been able to tell.


> Keep in mind to that for anything other than ASCII this is impossible, 
> for all practical purposes, to implement correctly using the strategy 
> you had in mind.

Yup. But these are filenames on a web server and will only be ASCII.

Thanks again

TjL

Re: input foo, output '[F|f][O|o][O|o]'?

[Lawrence Velázquez]

On Jul 1, 2013, at 8:58 PM, TJ Luoma <luomat@gmail.com> wrote:

> On 1 Jul 2013, at 14:44, ZyX wrote:
> 
>> By the way, what regex engine is your output for? Any I am aware of parse "[N|n]" as "either one of three characters: N, n, or pipe".
> 
> Really? I can think of several that support it. Maybe it's because I'm old enough to remember when a lot of these utilities didn't have 'ignore case'
> 
> % echo "foo\nbar\nbat" | egrep -v '[F|f]'
> bar
> bat
> 
> % echo "foo\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
> XXX
> bar
> bat

These regex are not matching what you think they are matching. For sure, "[F|f]" matches both lowercase and uppercase F, but as ZyX said, it also matches pipe characters:

    % echo "foo\nbar\nbaz\nbar|||baz" | egrep -v '[F|f]'
    bar
    baz

    % echo "foo\nbar\nbaz\nbar|||baz" | sed 's/[F|f][O|o][O|o]/XXX/g'
    XXX
    bar
    baz
    barXXXbaz

You are probably thinking of "(F|f)"; you should just use "[Ff]".

> You can also use it for matching case/esac :
> 
> case "$i" in
> 	[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n])
> 			echo "matched crashplan"
> 	;;
> 
> 	*)
> 			echo "No Match"
> 	;;
> 
> esac

Same misconception here; pipes in patterns' bracket expressions have no special meaning. You can remove all the pipes from your example, and it would still work.

    % case "crasHPLan" in
    case>           [Cc][Rr][Aa][Ss][Hh][Pp][Ll][Aa][Nn]) echo "matched";;
    case>           *) echo "did not match";;
    case> esac
    matched

vq

Re: input foo, output '[F|f][O|o][O|o]'?

[Benjamin R. Haskell]

On Mon, 1 Jul 2013, TJ Luoma wrote:

>
> On 1 Jul 2013, at 14:44, ZyX wrote:
>
>> [...]
>> By the way, what regex engine is your output for? Any I am aware of 
>> parse "[N|n]" as "either one of three characters: N, n, or pipe".
>
> Really? I can think of several that support it. Maybe it's because I'm old 
> enough to remember when a lot of these utilities didn't have 'ignore case'

I think you've missed the point of "N, n, or pipe".  [F|f] matches upper 
'F' or lower 'f', but also the character '|'.  You seem to be 
conflating:

[xyz] - 'x' or 'y' or 'z'

with:

(x|y|z) - 'x' or 'y' or 'z'

The '|' doesn't mean 'or' within square brackets.  It means the literal 
character: '|'.


> % echo "foo\nbar\nbat" | egrep -v '[F|f]'
> bar
> bat

% echo "foo\nb|r\nbat" | egrep -v '[F|f]'
bat
(It rejected 'b|r', because it contains '|', even though it doesn't 
contain 'F' or 'f')


> % echo "foo\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
> XXX
> bar
> bat

% echo "f|o\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
XXX
bar
bat
(It changed 'f|o' to 'XXX', despite '|' not being 'O' or 'o')


> You can also use it for matching case/esac :
>
> case "$i" in
> 	[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n])
> 			echo "matched crashplan"
> 	;;
>
> 	*)
> 			echo "No Match"
> 	;;
>
> esac

(Using a smaller example:)

i='|||'

case "$i" in
   [F|f][O|o][O|o]) echo matched foo ;;
   *) echo no match ;;
esac

will echo:
matched foo

You really just want:

[Cc][Rr][Aa][Ss][Hh][Pp][Ll][Aa][Nn])

Re: input foo, output '[F|f][O|o][O|o]'?

[ZyX]

02.07.13, 04:58, "TJ Luoma" <luomat@gmail.com>":
> 
> 
> On 1 Jul 2013, at 14:44, ZyX wrote:
> 
> > I do not think you will find a way to do this. All regex engines 
> > (precisely, programs that are using them) I know support a way to set 
> > case sensitivity for the whole regular expression and some support 
> > toggling this for a part of regular expression. In grep this is an -i 
> > switch, for vim it is either /i or \c/\C, for sed this is /i, for PCRE 
> > and perl this is additionally (?i) "atom" (additionally to other ways 
> > of toggling the behavior which are highly dependent on programs 
> > embedding PCRE; for perl this is usual /i flag). Even zsh globs do 
> > support (#i).
> 
> Phil Pennock's version worked great:
> 
> % foo=CrashPlan
> % for c in ${(s::)foo}; do print -n "[${(U)c}|${(L)c}]";done; print
> [C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]
> %

This is a bicycle. You asked for a standard way, you will not find it.

> 
> 
> > By the way, what regex engine is your output for? Any I am aware of 
> > parse "[N|n]" as "either one of three characters: N, n, or pipe".
> 
> Really? I can think of several that support it. Maybe it's because I'm 
> old enough to remember when a lot of these utilities didn't have 'ignore 
> case'
> 
> % echo "foo\nbar\nbat" | egrep -v '[F|f]'
> bar
> bat
> 
> % echo "foo\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
> XXX
> bar
> bat
> 
> You can also use it for matching case/esac :
> 
> case "$i" in
> 	[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n])
> 			echo "matched crashplan"
> 	;;
> 
> 	*)
> 			echo "No Match"
> 	;;
> 
> esac

It is not a disproof. Check it with pipe symbol in input.

> 
> 
> > I am also assuming XY problem here: what for do you need such 
> > conversion? You should consider lowercasing the tested string if 
> > nothing like -i is available.
> 
> It's for use with the AddDescription directive for .htaccess which (from 
> what I understand) takes its case sensitivity from the underlying 
> filesystem when matching filenames. There's no "ignore case" flag or 
> anything else that I can use with it, so my only option (at least, the 
> only one I can think of) is the one that I suggested. For example, if I 
> wanted to add this for any files which start with 'BBEdit' (case 
> insensitive) this is what I'd need to use:
> 
> 	AddDescription "<a href='http://barebones.com/bbedit'>A text editor 
> that doesn't suck</a>" [B|b][B|b][E|e][D|d][I|i][T|t]*
> 
> I verified that it works, but typing that stuff manually is tedious and 
> highly error prone, which made it the perfect place for a shell script 
> :-)

Unless AddDescription uses different regex engine then FilesMatch answer is in the first link if searching for "htaccess case insensitive regex": (?i:pattern).

Re: input foo, output '[F|f][O|o][O|o]'?

[ZyX]

02.07.13, 07:51, "ZyX" <kp-pav@yandex.ru>":
> 
> 
> 
> 02.07.13, 04:58, "TJ Luoma" <luomat@gmail.com>":
> > 
> > 
> > On 1 Jul 2013, at 14:44, ZyX wrote:
> > 
> > > I do not think you will find a way to do this. All regex engines 
> > > (precisely, programs that are using them) I know support a way to set 
> > > case sensitivity for the whole regular expression and some support 
> > > toggling this for a part of regular expression. In grep this is an -i 
> > > switch, for vim it is either /i or \c/\C, for sed this is /i, for PCRE 
> > > and perl this is additionally (?i) "atom" (additionally to other ways 
> > > of toggling the behavior which are highly dependent on programs 
> > > embedding PCRE; for perl this is usual /i flag). Even zsh globs do 
> > > support (#i).
> > 
> > Phil Pennock's version worked great:
> > 
> > % foo=CrashPlan
> > % for c in ${(s::)foo}; do print -n "[${(U)c}|${(L)c}]";done; print
> > [C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]
> > %
> 
> This is a bicycle. You asked for a standard way, you will not find it.
> 
> > 
> > 
> > > By the way, what regex engine is your output for? Any I am aware of 
> > > parse "[N|n]" as "either one of three characters: N, n, or pipe".
> > 
> > Really? I can think of several that support it. Maybe it's because I'm 
> > old enough to remember when a lot of these utilities didn't have 'ignore 
> > case'
> > 
> > % echo "foo\nbar\nbat" | egrep -v '[F|f]'
> > bar
> > bat
> > 
> > % echo "foo\nbar\nbat" | sed 's#[F|f][O|o][O|o]#XXX#g'
> > XXX
> > bar
> > bat
> > 
> > You can also use it for matching case/esac :
> > 
> > case "$i" in
> > 	[C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n])
> > 			echo "matched crashplan"
> > 	;;
> > 
> > 	*)
> > 			echo "No Match"
> > 	;;
> > 
> > esac
> 
> It is not a disproof. Check it with pipe symbol in input.
> 
> > 
> > 
> > > I am also assuming XY problem here: what for do you need such 
> > > conversion? You should consider lowercasing the tested string if 
> > > nothing like -i is available.
> > 
> > It's for use with the AddDescription directive for .htaccess which (from 
> > what I understand) takes its case sensitivity from the underlying 
> > filesystem when matching filenames. There's no "ignore case" flag or 
> > anything else that I can use with it, so my only option (at least, the 
> > only one I can think of) is the one that I suggested. For example, if I 
> > wanted to add this for any files which start with 'BBEdit' (case 
> > insensitive) this is what I'd need to use:
> > 
> > 	AddDescription "<a href='http://barebones.com/bbedit'>A text editor 
> > that doesn't suck</a>" [B|b][B|b][E|e][D|d][I|i][T|t]*
> > 
> > I verified that it works, but typing that stuff manually is tedious and 
> > highly error prone, which made it the perfect place for a shell script 
> > :-)
> 
> Unless AddDescription uses different regex engine then FilesMatch answer is in the first link if searching for "htaccess case insensitive regex": (?i:pattern).

It seems it does use different regex engine.

Re: input foo, output '[F|f][O|o][O|o]'?

[TJ Luoma]

On 1 Jul 2013, at 21:53, Benjamin R. Haskell wrote:

> I think you've missed the point of "N, n, or pipe".  [F|f] matches 
> upper 'F' or lower 'f', but also the character '|'.  You seem to be 
> conflating:
>
> [xyz] - 'x' or 'y' or 'z'
>
> with:
>
> (x|y|z) - 'x' or 'y' or 'z'
>
> The '|' doesn't mean 'or' within square brackets.  It means the 
> literal character: '|'.

Oh FFS… yes… sorry… that's exactly what I was doing. Sorry about 
that. I kept reading what I was thinking about instead of what I'd 
written.

*sigh*

(It's been a long week for it to be only just past Monday :-)

TjL

Re: input foo, output '[F|f][O|o][O|o]'?

[Phil Pennock]

On 2013-07-02 at 08:00 +0400, ZyX wrote:
> > > Phil Pennock's version worked great:
> > > 
> > > % foo=CrashPlan
> > > % for c in ${(s::)foo}; do print -n "[${(U)c}|${(L)c}]";done; print
> > > [C|c][R|r][A|a][S|s][H|h][P|p][L|l][A|a][N|n]

Sorry, I was in a rush and missed that this was [A|B] which should of
course be written [AB] or (A|B) if the regexp language supports the
latter.  I should have caught that, instead of answering exactly what
was asked.

> > Unless AddDescription uses different regex engine then FilesMatch
> > answer is in the first link if searching for "htaccess case
> > insensitive regex": (?i:pattern).
> 
> It seems it does use different regex engine.

AddDescription does not take a regex.  It takes a filename pattern, or
what in shell is called a Glob.

It happens that some shells use [AB] as a glob pattern too, also to
introduce a character class, and that's why it works -- Apache supports
that syntax also.

Those places in Apache that do take regexps use the PCRE engine, the one
written by Philip Hazel for Exim, and which zsh also supports with
"zmodload zsh/pcre" (or setting the option to change =~ to use it,
"setopt rematch_pcre", which will auto-load that module when you first
use =~).

So those places in Apache which want regexps, you can test with zsh to
get a decent approximation, or use the pcretest(1) tool from the PCRE
distribution to get something designed to interactively test regexps
against inputs.

If you want to settle on that syntax, also consider installing the
pcregrep tool.  It's very nice to be able to relax and just use PCRE
syntax, even though the PCRE implementation is not as efficient as the
older tools (or the newer RE2 system).

-Phil