Extract XML Value in bash script

Question

I m trying to extract a value from an xml document that has been read into my script as a variable  The original variable   data  is    lt item gt      lt title gt 15 54 57 - George  lt  title gt     lt description gt Diane DeConn  You saw Diane DeConn  lt  description gt    lt  item gt    lt item gt      lt title gt 15 55 17 - Jerry  lt  title gt      lt description gt Something huh  lt  description gt   lt  item gt     and I wish to extract the first title value  so   15 54 57 - George    I ve been using the sed command   title   sed -n -e  s    lt title gt        lt   title gt     1 p   lt  lt  lt   data    but this only outputs the second title value   15 55 17 - Jerry    Does anyone know what I have done wrong  Thanks

User · Answer

I agree with Charles Duffy that a proper XML parser is the right way to go.

But as to what's wrong with your sed command (or did you do it on purpose?).

$data was not quoted, so $data is subject to shell's word splitting, filename expansion among other things. One of the consequences being that the spacing in the XML snippet is not preserved.

So given your specific XML structure, this modified sed command should work

title=$(sed -ne '/title/{s/.*<title>\(.*\)<\/title>.*/\1/p;q;}' <<< "$data")

Basically for the line that contains title, extract the text between the tags, then quit (so you don't extract the 2nd <title>)

User · Answer

As Charles Duffey has stated  XML parsers are best parsed with a proper XML parsing tools  For one time job the following should work    grep -oPm1     lt   lt title gt     lt       Test     echo   data   lt item gt      lt title gt 15 54 57 - George  lt  title gt     lt description gt Diane DeConn  You saw Diane DeConn  lt  description gt    lt  item gt    lt item gt      lt title gt 15 55 17 - Jerry  lt  title gt      lt description gt Something huh  lt  description gt    title   grep -oPm1     lt   lt title gt     lt      lt  lt  lt    data     echo   title  15 54 57 - George

User · Answer

XMLStarlet or another XPath engine is the correct tool for this job   For instance  with data xml containing the following    lt root gt     lt item gt        lt title gt 15 54 57 - George  lt  title gt       lt description gt Diane DeConn  You saw Diane DeConn  lt  description gt      lt  item gt      lt item gt        lt title gt 15 55 17 - Jerry  lt  title gt        lt description gt Something huh  lt  description gt     lt  item gt   lt  root gt       you can extract only the first title with the following   xmlstarlet sel -t -m    title 1   -v   -n  lt data xml   Trying to use sed for this job is troublesome  For instance  the regex-based approaches won t work if the title has attributes  won t handle CDATA sections  won t correctly recognize namespace mappings  can t determine whether a portion of the XML documented is commented out  won t unescape attribute references  such as changing Brewster  amp amp  Jobs to Brewster  amp  Jobs   and so forth

[xml] Extract XML Value in bash script

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