kwik way?

[Devin Teske]

> -----Original Message-----
> From: owner-freebsd-questions at freebsd.org [mailto:owner-freebsd-
> questions at freebsd.org] On Behalf Of Devin Teske
> Sent: Wednesday, May 18, 2011 11:19 AM
> To: 'Gary Kline'; 'FreeBSD Mailing List'
> Subject: RE: kwik way?
> 
> > -----Original Message-----
> > From: owner-freebsd-questions at freebsd.org [mailto:owner-freebsd-
> > questions at freebsd.org] On Behalf Of Gary Kline
> > Sent: Wednesday, May 18, 2011 10:42 AM
> > To: FreeBSD Mailing List
> > Subject: kwik way?
> >
> > should i use tr or sed to turn "\t" into " "?  --i.e., tabs into spaces.
> 
> Depends on how you do it in sed. The y/// operator is faster than s/// when
> transliterating a single character globally.
> 
> If you use y/// instead of s///, then sed performance should be on-par with
tr.
> 
> Below are some performance metrics involving a 100,000 line contrived text
file
> containing 1M tabs and 1.8M spaces:
> 
> $ wc -l foo
>   100000 foo
> $ du -h foo
> 2.8M    foo
> $ file foo
> foo: ASCII text
> 
> $ time sh -c "sed -e 's/    / /g' < foo > bar"
> real    0m2.479s
> user    0m1.047s
> sys     0m0.105s
> $ md5 bar
> MD5 (bar) = f0187bcbc37cd6d84c6f5cadc6443843
> 
> $ time sh -c "tr '\t' ' ' < foo > bar"
> real    0m0.261s
> user    0m0.120s
> sys     0m0.026s
> $ md5 bar
> MD5 (bar) = f0187bcbc37cd6d84c6f5cadc6443843
> 
> $ time sh -c "sed -e 'y/    / /' < foo > bar"
> real    0m0.261s
> user    0m0.116s
> sys     0m0.087s
> $ md5 bar
> MD5 (bar) = f0187bcbc37cd6d84c6f5cadc6443843

In case you were thinking of either awk or perl, I'd recommend against those
given the following results:

$ time sh -c "awk '{gsub(/\t/,\" \");print}' < foo > bar"
real    0m2.769s
user    0m1.498s
sys     0m0.140s
$ md5 bar
MD5 (bar) = f0187bcbc37cd6d84c6f5cadc6443843

$ time sh -c "perl -pe 'tr/\t/ /' < foo > bar"
real    0m0.565s
user    0m0.277s
sys     0m0.137s
$ md5 bar
MD5 (bar) = f0187bcbc37cd6d84c6f5cadc6443843



> --
> Devin
> 
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