[gentoo-user] shell script

[gentoo-user] shell script

[scwang]

In a shellp script, let
       STRING="a.txt b.txt c.txt"
And I want to delete a sub-string from $STRING, for example
b.txt, and then we got
       $STRING is "a.txt c.txt"

How to achieve it?


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scwang
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[gentoo-user] Re: shell script

[Francesco Talamona]

On Tuesday 18 April 2006 07:34, scwang@ios.ac.cn wrote:
> In a shellp script, let
>        STRING="a.txt b.txt c.txt"
> And I want to delete a sub-string from $STRING, for example
> b.txt, and then we got
>        $STRING is "a.txt c.txt"
>
> How to achieve it?

http://www.tldp.org/LDP/abs/html/string-manipulation.html

ciao
	Francesco
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Re: [gentoo-user] shell script

[Zac Slade]

On Tuesday 18 April 2006 00:34, scwang@ios.ac.cn wrote:
> In a shellp script, let
>        STRING="a.txt b.txt c.txt"
> And I want to delete a sub-string from $STRING, for example
> b.txt, and then we got
>        $STRING is "a.txt c.txt"
>
> How to achieve it?
>From man bash:
${parameter:-word}
Use Default Values.  If parameter is unset or null, the expansion of word is 
substituted.  Otherwise, the value of parameter is substituted.

So for what you want just do:
STRING="a.txt b.txt c.txt"
${STRING:-b.txt}

There are tons of ways to manipulate "parameters" and you should reference the 
man page for more.  Look under "Parameter Expansion" for all the 
possibilities.
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Zac Slade
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Re: [gentoo-user] shell script

[Benno Schulenberg]

Zac Slade wrote:
> On Tuesday 18 April 2006 00:34, scwang@ios.ac.cn wrote:
> > In a shellp script, let
> >        STRING="a.txt b.txt c.txt"
> > And I want to delete a sub-string from $STRING, for example
> > b.txt, and then we got
> >        $STRING is "a.txt c.txt"
>
> So for what you want just do:
> STRING="a.txt b.txt c.txt"
> ${STRING:-b.txt}

That doesn't work.  This does:

$ STRING="a.txt b.txt c.txt"
$ REMOVE="b.txt"
$ echo ${STRING/$REMOVE/}
a.txt c.txt

Benno
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Re: [gentoo-user] shell script

[Boyd Stephen Smith Jr.]

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On Tuesday 18 April 2006 07:11, Benno Schulenberg 
<benno.schulenberg@gmail.com> wrote about 'Re: [gentoo-user] shell 
script':
> Zac Slade wrote:
> > On Tuesday 18 April 2006 00:34, scwang@ios.ac.cn wrote:
> > > In a shellp script, let
> > >        STRING="a.txt b.txt c.txt"
> > > And I want to delete a sub-string from $STRING, for example
> > > b.txt, and then we got
> > >        $STRING is "a.txt c.txt"
> >
> > So for what you want just do:
> > STRING="a.txt b.txt c.txt"
> > ${STRING:-b.txt}
>
> That doesn't work.  This does:

Yeah, I don't know why someone would ever think that
STRING="a.txt b.txt c.txt"
made STRING empty or undefined. Or why substituting in the value "b.txt" 
would give the desired "a.txt c.txt".

(Hi Zac! :P)

> $ STRING="a.txt b.txt c.txt"
> $ REMOVE="b.txt"
> $ echo ${STRING/$REMOVE/}
> a.txt c.txt

However, it actually leave an extra space in the variable, which got 
swallowed by your shell since you didn't quote the expansion. Following 
the above with:
$ echo "${STRING/$REMOVE/}"
a.txt  c.txt

You might try either including the leading or trailing space in REMOVE or 
running the string through shell expansion (as you did by calling echo 
without quoting the expansion)

The original poster might want to look into bash arrays, esp. since the 
${VARIABLE/MATCH/REPLACEMENT} expansion doesn't work in sh either (so we 
are already into bash-specific shell), AFAIK.  

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it's that the vast majority of our users don't have the slightest
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