CODEWITHSUNDEEP
regexbashurlreplaceparameters
shEez
shEez

Reputation: 13

How to alter URL Parameters in Bash?

I've got the following Problem:

I would like to alter the parameters of an URL. My idea was to first cut the parameters as a whole like that:

url="http://domain.com/file.php?par1=val1&par2=val2&par3=val3"
pars=$(cut -d"?" -f2 <<< $url)

So now

echo "$pars"

should give me a list of Parameters seperated by the "&" character.

par1=val1&par2=val2&par3=val3

I want to replace val1 with the variable $newpar then use curl to visit the website with the changed parameter. Then i want to change the parameter back to val1 and change val2 to $newpar and so on. My question is: How do I do that?

I don't know how much parameters there will be, because the $url variable is read out of a file with URLs with a different number of parameters. I think some kind of regex would come in handy and also that probably a for loop would do the trick. But I don't know exactly how.

Thank you very much in advance

Upvotes: 1

Views: 504

Answers (1)

chepner
chepner

Reputation: 531125

Assuming var1 is specific enough, the following should work:

url=${url/par1=val1/par1=$newpar}

The only problem would be if par1 could be the suffix of another parameter, like

url="http://domain.com/file.php?par1=val1&otherpar1=val2&par3=val3"

In that case, use a regular expression to ensure par1 is preceded by either & or ?:

[[ $url =~ (.*)([?&])(par1=val1)(.*) ]]
url="${BASH_REMATCH[1]}${BASH_REMATCH[2]}par1=$newpar${BASH_REMATCH[4]}"

Element 1 contains everything before the ? or & that precedes the parameter you want to change. Element 2 contains the ?/&. Element 2 is the text you want to replace; we use the replacement text instead of that element. Finally, element 3 contains the text, if any, that follows the parameter you are changing.

Upvotes: 1

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