when i change use 5.16.0; to use feature ':5.10'; it works i get following output
bash-4.2$ ./regex.pl Use of uninitialized value $3 in say at ./regex.pl line 7, <DATA> line 1. Use of uninitialized value $4 in say at ./regex.pl line 7, <DATA> line 1. Video1280x720 Use of uninitialized value $2 in say at ./regex.pl line 7, <DATA> line 2. Use of uninitialized value $3 in say at ./regex.pl line 7, <DATA> line 2. Use of uninitialized value $4 in say at ./regex.pl line 7, <DATA> line 2. Audio Use of uninitialized value $2 in say at ./regex.pl line 7, <DATA> line 3. Use of uninitialized value $3 in say at ./regex.pl line 7, <DATA> line 3. Use of uninitialized value $4 in say at ./regex.pl line 7, <DATA> line 3. Subtitle how these two use statements differ. use 5.16.0; perl regex.pl works why ./regex.pl doesnt work. it gives following error feature version v5.16.0 required--this is only version v1.160.0 at ./ regex.pl line 4. BEGIN failed--compilation aborted at ./regex.pl line 4. On Wed, Sep 17, 2014 at 2:38 PM, Uday Vernekar <vernekaru...@gmail.com> wrote: > When i run this script i get following Error > > bash-4.2$ ./regex.pl > feature version v5.16.0 required--this is only version v1.160.0 at ./ > regex.pl line 4. > BEGIN failed--compilation aborted at ./regex.pl line 4. > > > > But I am using perl version as swon below. > > bash-4.2$ perl -v > > This is perl 5, version 16, subversion 3 (v5.16.3) built for i686-linux > > Copyright 1987-2012, Larry Wall > > Perl may be copied only under the terms of either the Artistic License or > the > GNU General Public License, which may be found in the Perl 5 source kit. > > Complete documentation for Perl, including FAQ lists, should be found on > this system using "man perl" or "perldoc perl". If you have access to the > Internet, point your browser at http://www.perl.org/, the Perl Home Page. > > > > > On Wed, Sep 17, 2014 at 8:52 AM, Jing Yu <logus...@googlemail.com> wrote: > >> Hi Viet-Duc Le, >> On 17 Sep 2014, at 10:23, Viet-Duc Le <leviet...@kaist.ac.kr> wrote: >> >> Greeting from S. Korea ! >> >> I am parsing the output of ffmpeg with perl. Particular, I want to print >> only >> these lines among the output and capturing the resolution, i.e. 1280x720. >> .... >> >> Stream #0:0: Video: h264 (High), yuv420p, 1280x720, SAR 1:1 DAR 16:9, 23.98 >> fps, 23.98 tbr, 1k tbn, 47.95 tbc (default) >> Stream #0:1(jpn): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s (default) >> Stream #0:2(eng): Subtitle: ass (default) >> ..... >> >> My code is following: >> # INFO is pipe to ffmpeg >> # Here, the <print "$1 $2 $3 $4\n"> is for debugging . >> while ( <INFO> ) { >> if ( <regular expression> ) { >> print "$1 $2 $3 $4\n"; >> } >> } >> >> Desirable outputs: >> -> Video 1280 720 >> Audio >> Subtitle >> >> Regarding the <regular expession>: >> 1. /Stream #\d:\d.*(Video|Audio|Subtitle).*(\d+)x(\d+)/ (greedy) >> -> Video 0 720 >> >> Q: why does $2 give 0? I remember .* match backward starting from the end >> of the string. Then it should be "Video 1280 720" as output. >> >> that '0' is from 128'0', since the '.*' consumes 128. What it does under >> the hood is .* first will reach to the end of the target string, and then >> backtract according to the following regex. Once the whole regex is >> satisfied, it will stop backtracting, although further retracting will >> possibly also satisfy the regex. >> >> >> 2. /Stream #\d:\d.*(Video|Audio|Subtitle).*?(\d+)x(\d+)/ (non greedy) >> -> Video 1280 720 >> Q: I can understand this, but again I think (1) should work too. >> >> >> 3. /Stream #\d:\d.*(Video|Audio|Subtitle).*?(?:(\d+)x(\d+))?/ ( >> non-capturing optional group ) >> -> Video >> Audio >> Subtitle >> Q: It seems that the resolution part >> is ignored because it is optional. Otherwise, the output will contains >> "Video" only as (1) and (2). How can I circumvent this ? >> >> that ?: prevents $ variables to capture the matching regex group. I guess >> you can get rid of it. The trailing ? already tells the regex group to >> match optionally. It is equivalent to {0,1}. The big problem coming with it >> is the middle .*?. Since the last part is optional, .*? will just match the >> least number of char possible, which is nothing. >> >> >> 4. /Stream #\d:\d.*(Video|Audio|Subtitle).+?(?:(\d+)x(\d+))?.*?$/ >> -> Video >> Audio >> Subtitle >> >> Q: I tried to match things after the resolution, hoping that it will be >> captured. >> >> >> Again the ?: prevents it being captured. .+? in the middle is better, now >> it matches ':'. >> >> >> >> 5. /Stream #\d:\d.*(Video|Audio|Subtitle).+?(?:(\d+)x(\d+))?(.*?)$/ ( let's >> capture the last part) >> >> -> Video h264 (High), yuv420p, 1280x720, SAR 1:1 DAR 16:9, 23.98 fps, >> 23.98 tbr, 1k tbn, 47.95 tbc (default) >> Audio ac3, 48000 Hz, stereo, fltp, 192 kb/s (default) >> Subtitle ass (default) >> Q: Now $2 and $3 is undef, and the rest of the string went to $4. Again, I am >> quite puzzled by the output. >> >> If it is optional, it is non greedy. So everything goes to the (.*?)$. >> >> >> Please pardon my long email. I hope someone can point out the flaws in my >> logic. >> Here, I can match and print Video/Audio/Subtitle separately. >> But I wish for one expression to match them all, one expression to print >> them. >> >> In general, it is a better practise to add 'x' to your regex to make it >> more readable. My regex might not be the best, but it works as expected. >> >> use strict; >> use warnings; >> use 5.16.0; >> >> while(<DATA>){ >> / (Video|Audio|Subtitle) (?: (?:.) +? (\d+x\d+) || (?:.)+ ) /x >> and say $1, $2, $3, $4; >> } >> >> >> __DATA__ >> Stream #0:0: Video: h264 (High), yuv420p, 1280x720, SAR 1:1 DAR 16:9, >> 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default) >> Stream #0:1(jpn): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s (default) >> Stream #0:2(eng): Subtitle: ass (default) >> >> The '||' operator will first check the group before it. It will only look >> at the other group if the first group fails. This puts your resolution >> group matching as priority, but not necessity. >> >> Hope this helps. >> Jing >> >> > > > -- > ********************************************************* > Don't ask them WHY they hurt you, > because all they'll tell you is lies and excuses. > Just know they were wrong, and try to move on. > ********************************************************** > -- ********************************************************* Don't ask them WHY they hurt you, because all they'll tell you is lies and excuses. Just know they were wrong, and try to move on. **********************************************************
