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overflow
LXF regular
Joined: Tue Aug 23, 2005 2:40 pm
Posts: 158
Location: London
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 Posted: Fri Jun 02, 2006 3:55 pm Post subject: Testing Bash arrays for a string |
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I'm trying to test a Bash array for any element containing a string. A whole element and the whole string - no substrings.
Long-hand, I could do it like this:
| Code: | myset=(oak pine beach elm)
for i in ${myset[@]}; do if [[ $i == ${tree} ]] ; then ... ; fi; done
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which seems a bit long-winded.
Or I could almost do it like this:
| Code: | myset=(oak pine beach elm)
if [[ ${myset[*]} =~ ${tree} ]] ; then ... ; fi
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Which is tidier but suffers from a drawback: it will match substrings. It matches 'pin', for example.
I can force word boundaries to overcome the substring problem, like this:
| Code: | myset=(oak pine beach elm)
if [[ ${myset[*]} =~ \\b${tree}\\b ]] ; then ... ; fi
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but it still isn't very elegant.
Anyone got a better approach?
Thanks
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Steogede
LXF regular
Joined: Thu May 04, 2006 6:39 pm
Posts: 146
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| Posted: Mon Jun 19, 2006 11:39 am Post subject: RE: Testing Bash arrays for a string |
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My honest opinion, the first option seems fine. Okay it is a bit verbose, but verbosity is often a useful thing - indeed, it is one of the main reason we use high level programming languages rather than doing everything in assembly. The only thing which seems to be missing from option 1 is an exit statement to take you out of the for loop once you have found a match.
As for elegance, I think that is a matter of taste, your first solution seems perfectly elegant. I don't really see how it could be more elegant. You could make it more efficient perhaps, option 3 has that covered. The only thing you could add to (or take away from) option 3 is to make it more terse. If you wanted something more terse you could use [[ test ]] && whatever. e.g: | Code: |
myset=(oak pine beach elm)
seaside="beach"
[[ ${myset[*]} =~ \\b${seaside}\\b ]] && echo "${myset[*]} contains $seaside" |
What were you hoping for in terms of elegance? Do you have an example from another programming language? |
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overflow
LXF regular
Joined: Tue Aug 23, 2005 2:40 pm
Posts: 158
Location: London
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| Posted: Mon Jun 19, 2006 11:51 am Post subject: RE: Testing Bash arrays for a string |
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Well, how about Python: | Code: | myset=('oak', 'pine', 'beach', 'elm')
if tree in myset:
...do something
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It doesn't get much tidier than that.
I'm not sure I get your point about verbosity. High level languages more verbose than assembly language? How's that?
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Steogede
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Joined: Thu May 04, 2006 6:39 pm
Posts: 146
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| Posted: Mon Jun 19, 2006 5:08 pm Post subject: Re: RE: Testing Bash arrays for a string |
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| overflow wrote: | Well, how about Python: | Code: | myset=('oak', 'pine', 'beach', 'elm')
if tree in myset:
...do something
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It doesn't get much tidier than that. |
I don't script in bash a great deal, but I would be surprised if there was a neater option than you have already posted. You could create a function to check if the element exists, then use that in an if statement e.g. if exists(elem,arr) ...
| Quote: | | I'm not sure I get your point about verbosity. High level languages more verbose than assembly language? How's that? |
Sorry, your right, that makes no sense. My mind tends to wander of on its own sometimes. |
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