Perl Regex with unix grep command

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Hello,

According to the grep manual page I can use the -P option to use Perl
regular expressions as follows:

grep -P PERL_REGEX INPUT_FILE

however, I cannot get the following pattern to match a literal dollar sign:

grep -P makan\$ file.txt

when I know this pattern is in the file. It matches the shorter string
without the dollar sign if I leave \$ out.

Thanks,

Jon

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Re: Perl Regex with unix grep command

On 11-09-03 05:01 PM, Jon Forsyth wrote:
> Hello,
>
> According to the grep manual page I can use the -P option to use Perl
> regular expressions as follows:
>
> grep -P PERL_REGEX INPUT_FILE
>
> however, I cannot get the following pattern to match a literal dollar sign:
>
> grep -P makan\$ file.txt

# You have to get the backslash past the shell

grep -P 'makan\$' file.txt

# or

grep -P makan\\$ file.txt


>
> when I know this pattern is in the file. It matches the shorter string
> without the dollar sign if I leave \$ out.
>
> Thanks,
>
> Jon
>


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Re: Perl Regex with unix grep command

>>>>> "JF" == Jon Forsyth writes:

JF> According to the grep manual page I can use the -P option to use
JF> Perl regular expressions as follows:

JF> grep -P PERL_REGEX INPUT_FILE

just to let you know, nothing but perl can run perl regexes. all the
ones that claim it are doing subsets and in some cases not even close
anymore.

JF> however, I cannot get the following pattern to match a literal
JF> dollar sign:

JF> grep -P makan\$ file.txt

you are escaping that from the shell but the 'perl' regex will then make
it match the end of a line or before a newline. you need to quote it
against the shell with '' and keep the \ in there.

uri

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Re: Perl Regex with unix grep command

Hi all,

On Sat, 03 Sep 2011 17:15:51 -0400
Shawn H Corey wrote:

> On 11-09-03 05:01 PM, Jon Forsyth wrote:
> > Hello,
> >
> > According to the grep manual page I can use the -P option to use Perl
> > regular expressions as follows:
> >
> > grep -P PERL_REGEX INPUT_FILE
> >
> > however, I cannot get the following pattern to match a literal dollar s=
ign:
> >
> > grep -P makan\$ file.txt
>=20
> # You have to get the backslash past the shell
>=20
> grep -P 'makan\$' file.txt
>=20
> # or
>=20
> grep -P makan\\$ file.txt
>=20

Just to be a bit more pedantic, in this case:

grep -P makan\\\$ file.txt=20

would be safer and more idiomatic, because otherwise the shell would treat =
the
string as a literal backslash followed by the opening of a shell variable,
which all start with "$".

Regards,

Shlomi Fish


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