Re: efficient way to use matched string in variable substitution

[L A Walsh]

On 2021/08/24 05:06, Greg Wooledge wrote:
> Looks like the efficiency of "read -ra" vs. a shell loop just about makes
> up for the system calls used for the here string (f6 and f7 are almost
> tied in overall speed, with f6 just a *tiny* bit faster).  Good to know.
>
>   
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If you set your TIMEFORMAT -- I put this in my login scripts:
export TIMEFORMAT="%2Rsec %2Uusr %2Ssys (%P%% cpu)"

the 4th field can give a feel for parallelism:

fn1() { /usr/bin/ls -1 /usr/bin >/tmp/tt && wc </tmp/tt && rm /tmp/tt ; 
}     
fn2() { /usr/bin/ls -1 /usr/bin  | wc ; }
time fn1 >/dev/null
0.01sec 0.01usr 0.00sys (101.56% cpu)
time fn2 >/dev/null
0.01sec 0.00usr 0.00sys (134.03% cpu)