kwik way?

[Devin Teske]

> -----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
-- 
Devin

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