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Full Discussion: Trouble with sed and substituting a string with special characters in variable
Top Forums Shell Programming and Scripting Trouble with sed and substituting a string with special characters in variable Post 302649575 by bakunin on Thursday 31st of May 2012 05:09:56 PM
Old 05-31-2012
You have told us everything - save for the contents of "$marker" and "$markerrepl", which would be the only thing necessary to know. How am i - how are we - supposed to give you advice regarding a string when we don't know the string?

I hope you aren't too dissatisfied with an answer which will be of only general nature:

Quote:
Originally Posted by ampsys
Code:
sed -i "s/$marker/$markerrepl/g" $formattedfile

When substituting from variable contents there are a few problems. The first is that this is prone to "injections" - a part of the search- or replacement-string will constitue a sed command itself. The output will probably not be what you had in mind. Example:

Code:
a="abc"
b="xyz"

sed "s/$a/$b/" /some/file       # will work as expected

a="abc/xyz"
sed "s/$a/$b/" /some/file       # will not work

A solution for this will be to escape all the characters special to sed prior to useing these strings. Escaping in sed is done with backslashes:

Code:
a="abc\/xyz"
b="xyz"

sed "s/$a/$b/" /some/file       # will work as expected


A second problem is shell-related: without quoting variables can break up lines into pieces. This can be partly overcome with proper quoting:

Code:
a="a b c"
b="x y"

sed s/$a/$b/ /some/file            # will not work
sed 's/'"$a"'/'"$b"'/g' /some/file # will work

This will not help you if variables contain line feeds.

I hope this helps.

bakunin
Last edited by bakunin; 06-01-2012 at 05:49 AM..
 

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LEARN ABOUT DEBIAN

rdf::query::algebra::namedgraph

RDF::Query::Algebra::NamedGraph(3pm)			User Contributed Perl Documentation		      RDF::Query::Algebra::NamedGraph(3pm)

NAME

       RDF::Query::Algebra::NamedGraph - Algebra class for NamedGraph patterns

VERSION

       This document describes RDF::Query::Algebra::NamedGraph version 2.908.

METHODS

       Beyond the methods documented below, this class inherits methods from the RDF::Query::Algebra class.

       "new ( $graph, $pattern )"
	   Returns a new NamedGraph structure.

       "construct_args"
	   Returns a list of arguments that, passed to this class' constructor, will produce a clone of this algebra pattern.

       "graph"
	   Returns the graph node of the named graph expression.

       "pattern"
	   Returns the graph pattern of the named graph expression.

       "quads"
	   Returns a list of the quads belonging to this NamedGraph.

       "sse"
	   Returns the SSE string for this algebra expression.

       "explain"
	   Returns a string serialization of the algebra appropriate for display on the command line.

       "as_sparql"
	   Returns the SPARQL string for this algebra expression.

       "as_hash"
	   Returns the query as a nested set of plain data structures (no objects).

       "as_spin ( $model )"
	   Adds statements to the given model to represent this algebra object in the SPARQL Inferencing Notation (<http://www.spinrdf.org/>).

       "type"
	   Returns the type of this algebra expression.

       "referenced_variables"
	   Returns a list of the variable names used in this algebra expression.

       "potentially_bound"
	   Returns a list of the variable names used in this algebra expression that will bind values during execution.

       "definite_variables"
	   Returns a list of the variable names that will be bound after evaluating this algebra expression.

       "qualify_uris ( \%namespaces, $base_uri )"
	   Returns a new algebra pattern where all referenced Resource nodes representing QNames (ns:local) are qualified using the supplied
	   %namespaces.

AUTHOR

	Gregory Todd Williams <gwilliams@cpan.org>

perl v5.14.2							    2012-01-31				      RDF::Query::Algebra::NamedGraph(3pm)
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