The answer to your question is using awk.

See, for counting the read length, use :

awk '{if(NR%4==2) print NR"\t"$0"\t"length($0)}' file.fastq > readLength

Output:

 2    ATCTCATTTTTCACGTTTTTTAGTGATTTCATAATTTTTCAAGTCGTAAAGTGGATGTTTCTCATTTTTCATGATT    76
 6    GTGTTAGGTGCCAAGATCCTTCTGTGTTTAAAGTGCCTTCAGGGGTGAGTGGTTTTAGTGCCATGTACTGTGGAAA    76
10    TGTATGGAGTGTTTAGATGCTCCCTTCTAGCTTCTTTTCAGACAATTTACTAGGATGATTGACAGAGAATTGCTTT    76
14    ACTGTAGCCCCGCCACACTGCCACTGGTATAGGACACCAAAAAGCACTCTCTAATAAATACAGAAAGATTAGCAGA    76
18    ACGCTGGAAACTTAGACTAGCAGTTAGAATGTAGTGGTTGATAGAGCATCCAGCAACCAGGGGTAAACTCGGCCTC    76
22    TTTTTAGTGATTTCGTCATTTTTCAAGTCGTCAAGTGGATGTTTCTCATTTTCCATGATTTTCAGTTTTCCTCGCC    76
26    CAGCAAGCGAAATAGTTATGGCCCATGTTTTCTGGATATCAATTACACAACGGGGAGATTTGGAAGGAGAACATGC    76
30    CATTTCACATGAGTGAGACTCAAGGCTTGGGATGTGTAATACAAGATCAACACTTGGGACAAATTCCAGCATGGGG    76

where first column is the line number in the original fastq file, 2nd is the read in light and third the length of this read

and for the quality length, use :

awk '{if(NR%4==0) print NR"\t"$0"\t"length($0)}' file.fastq > qualityLength

 4    1==DDBEEHHHHDHIHIIIIIFHEHAGGHGIHIGHIIIIGGIIIGAFIIIGDGIHIIHCIIIHEHGEIII@HHGC?    76
 8    BBBFFFFFFHHHHHIGIJJIJIJJJIJIJJIJIHHGHIIIIJJJJ?DFHDFHHIIJJJIIIIJJJJJJJHFHGFGC    76
12    ??@D?D?DFFFDFGGIGH@>IHG@FGAA+CFF>9CGH@9DDH@GGICH<B@FHIBEH<GG@BF<BB=CA;F)7@GC    76
16    @@@DDDDDF>FFHIIGIGEGG??BFEC?9CFFE9DDGAGDDDF<CBE@FEHHGGHEDGHGHBA>EEEDCCBCCCCA    76
20    CCCFFFFFGHHHHJJJJJJIHIJHHGJIIIJHIJFHGADHGHGHDGIIIIIIJJIJJJJJJJI@GIHHHHH=BE?@    76
24    BCCFFDFDHHHHHJJJJJJJJJJGIIJJGHIIJIJ?FHCEHDGIJJIJJJJJIJJJJIJJJJIGJIIJJJIIGIGB    76
28    @CCDDFFDHHFHHJFGEGIIIIJAHGEEDGHGICHEEIIJ@HEEGIIJDCHHIIJ>EACEHFF?@DCEDCB>ACCD    76
32    @@@FFDDDHHDDDFHIJGIIGCGGIIIIIJJGHHCF1:FGFGIGGGHHIJJJDHGHIGHIIIGIJIIJIGHGHHHH    76

and finally, use awk again to compare the columns, here the column number 3

awk 'NR==FNR{a[$3]++;next}!a[$3]' readLength qualityLength

This will output the lines where the length is not matched, the output will be from the 2nd file.

FastQC will tell you the overall picture but this will exactly tell you what you want.

HTH

Edit : The code is better now as no need to use diff and to calculate the line number back (as suggested by @Istvan)

simple Perl solution reporting problematic reads:

#!/usr/bin/perl
use strict; 
use warning;
my ($read, $seqLen, $qualLen);
my $nl = 0;
while (<>)  {
    chomp;
    $nl++;
    if ($nl == 1) { 
        $read = $_; 
    }
    elsif ($nl == 2) { 
        $seqLen = length $_; 
    }
    elsif ($nl == 4) { 
        $qualLen = length $_;
        print "$read\t$seqLen != $qualLen\n" if ($seqLen != $qualLen);
        $nl   = 0;
    }
}

Use FastQC to get quality control metrics of NGS-reads. It has a Graphical User Interface and a command line interface as well. I think you can say FastQC is the most frequently used read quality control tool there is.

They even have a video tutorial to explain you how to use and interpret FastQC