Re: About Shell proggramming.

[Squirrel <jsli@ict.ac.cn>]

> On 27-May-2002 Squirrel wrote:
> > apt_dest()
> > {
> >       local m="$3"
> >       m="debootstrap.invalid"
> >       printf "$APTSTATE/lists/"
> >       echo "${m}_$4"|sed 's/\//_/g'
> > }
> > 
> > apt_dest rel woody file:/instmnt dists/woody/Release
> 
> each argument is passed in as a number parameter.   So $3 is the third
> argument.
$3=file:/instmnt?
>  
> > 
> > what's the meaning of the above program,especial of "echo "${m}_$4"|sed
> > 's/\//_/g"?
> > 
echo "${m}_$4" 
	means echo "debootstrap.invalid_dists/woody/Release'?
> 
> sed is a utility which reads input and does modifications to it then outputs it.
> 
> thr s///g means "do a string substitute with this regex on all occurances of
> the regex".  The item in between the first // is "\/" which is a backslash
> escaped, the item in the second // is '_'.  So this says send the fourth
> command line parameter into sed, changing all backslashes into underscores.
> 



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