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pacho2
Developer
Joined: 04 Mar 2005
Posts: 2599
Location: Oviedo, Spain
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 Posted: Thu Mar 21, 2019 11:11 am Post subject: awk: compare two variables containing parenthesis |
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Hello, I am having issues to compare two variables when they contain a parenthesis. For example this case works fine:
| Code: | BEGIN{
new="test"
global="test"
if(global~new) {print "Contains"} else {print "Doesn't contain"}
}
$ awk -f test.awk pp
Contains
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But this fails: | Code: |
BEGIN{
new="test(M)"
global="test(M)"
if(global~new) {print "Contains"} else {print "Doesn't contain"}
}
$ awk -f test.awk pp
Doesn't contain
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I have tried to escape (with double \\) the parenthesis but still doesn't work.
Thanks a lot for your help |
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guitou
Guru
Joined: 02 Oct 2003
Posts: 534
Location: France
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| Posted: Thu Mar 21, 2019 1:34 pm Post subject: |
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Hello.
You probably made a mistake when trying without double backslahes... seems to work on my comp:
| Code: |
$ cat bin/test.awk
#!/usr/bin/awk
BEGIN{
global="test(M)"
new="^test\\(M\\)$"
if(global ~ new) {print global " matches " new} else {print global " doesn't match " new}
}
$ awk -f bin/test.awk
test(M) matches ^test\(M\)$
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++
Gi) |
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pacho2
Developer
Joined: 04 Mar 2005
Posts: 2599
Location: Oviedo, Spain
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| Posted: Thu Mar 21, 2019 3:52 pm Post subject: |
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I think the problem is related with the new variable needing to escape the () but not the "global" one, because I am checking in a bigger script with this logic and it still fails (as that variable with parenthesis comes from another two variables like newvar=name"("value")"
The idea is to append "newvar" to "global" only when its values are not already there (this is inside a loop):
if(global!~new) {global=global""new";"}
But I guess now I will need to set a "new_to_compare" variable with the escapes while still appending the one without
new_to_compare=name"\\("value"\\)"
if(global!~new_to_compare) {global=global""new";"} |
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pacho2
Developer
Joined: 04 Mar 2005
Posts: 2599
Location: Oviedo, Spain
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| Posted: Thu Mar 21, 2019 4:06 pm Post subject: |
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Yes, that works 
Thanks! |
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Hu
Moderator
Joined: 06 Mar 2007
Posts: 21633
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| Posted: Fri Mar 22, 2019 1:43 am Post subject: |
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| If you want substring matching, wouldn't it be easier to use index to perform a substring search instead of trying to coerce the candidate string to be regex-safe? |
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krinn
Watchman
Joined: 02 May 2003
Posts: 7470
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| Posted: Fri Mar 22, 2019 2:43 pm Post subject: |
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agree with Hu, you're fixing the () case, but any special regex case will hit you
you're using a function to compare left argument with the regex result of right argument, not quiet sane for a string comparaison
And you can see how weak it is, if new is just an empty string
| Code: | cat bin/test.awk
#!/usr/bin/awk
BEGIN{
global="test(M)"
new=""
if(global ~ new) {print global " matches " new} else {print global " doesn't match " new}
}
$ awk -f bin/test.awk
test(M) matches
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pacho2
Developer
Joined: 04 Mar 2005
Posts: 2599
Location: Oviedo, Spain
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| Posted: Sat Mar 23, 2019 2:08 pm Post subject: |
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OK, thanks for the suggestion, I will look into it  |
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