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urldecoding with one pure BASH builtin

Terminal - urldecoding with one pure BASH builtin
VAR="%23%21%2fbin%2fbash" ; printf -v VAR "%b" "${VAR//\%/\x}" ; echo $VAR
2012-01-06 22:09:01
User: Corona688
Functions: echo printf
3
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urldecoding with one pure BASH builtin

You can use ordinary printf to convert "%23%21%2fbin%2fbash" into "#!/bin/bash" with no external utilities, by using a little known printf feature -- the "%b" specifier converts shell escapes. Replace % with \x and printf will understand the urlencoded string.

BASH's printf has an extension to set a variable directly, too. So you get to convert urlencoded strings from garble to plaintext in one step with no externals and no backticks.

Show sample output | Add to favourites | Report as malicious

Alternatives

There are 2 alternatives - vote for the best!

Terminal - Alternatives
sed -e's/%\([0-9A-F][0-9A-F]\)/\\\\\x\1/g' | xargs echo -e
2009-05-25 05:37:44
User: mohan43u
Functions: echo sed xargs
Tags: bash sed xa urldecod
10
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urldecoding
echo "http%3A%2F%2Fwww.google.com" | sed -e's/%\([0-9A-F][0-9A-F]\)/\\\\\x\1/g' | xargs echo -e

http://www.google.com

Works under bash on linux. just alter the '-e' option to its corresponding equivalence in your system to execute escape characters correctly.

Comments (3) | Add to favourites | Report as malicious
perl -pe 's/%([0-9a-f]{2})/sprintf("%s", pack("H2",$1))/eig'
2009-11-25 14:32:50
User: putnamhill
Functions: perl
Tags: perl urldecode
3
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urldecoding
Comments (0) | Add to favourites | Report as malicious
printf $(echo -n $1 | sed 's/\\/\\\\/g;s/\(%\)\([0-9a-fA-F][0-9a-fA-F]\)/\\x\2/g')
2009-11-25 04:27:39
User: infinull
Functions: echo printf sed
Tags: bash sed xa urldecod
2
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urldecoding

My version uses printf and command substitution ($()) instead of echo -e and xargs, this is a few less chars, but not real substantive difference.

Also supports lowercase hex letters and a backslash (\) will make it through unescaped

Show sample output | Comments (0) | Add to favourites | Report as malicious
ls * | while read fin;do fout=$(echo -n $fin | sed -e's/%\([0-9A-F][0-9A-F]\)/\\\\\x\1/g' | xargs echo -e);if [ "$fout" != "$fin" ];then echo "mv '$fin' '$fout'";fi;done | bash -x
2011-05-18 07:24:54
User: pawelb1973
Functions: bash echo ls read sed xargs
Tags: bash sed xa urldecod
0
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urldecoding

urldecode files in current directrory

Comments (0) | Add to favourites | Report as malicious

Know a better way?

If you can do better, submit your command here.

What others think

is there a way to encode with printf too ?

Comment by glaudiston 18 weeks ago

not in one line

cat file | sed -e's/%\([0-9A-F][0-9A-F]\)/\\\\\x\1/g' | xargs -L 1 echo -e

Comment by qwer 9 weeks ago

Use of only shell builtins has to win points over pipes and writing one line perl programs, slick fix Corona

Comment by teknopaul 3 weeks and 3 days ago

Your point of view

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