Replace userinput with forward sladh (/)

Shell Programming and Scripting
1

Hi All,

If I wanted to find and replace a line with a user input value that has forward slash, then how to do it?

For example I have a script called ./configure.sh which will ask for user to input some path (let's say WPS_HOME). I can read that user input and want to put this value to a configuration file by searching for a string and replace that entire line with user input value. Using following command I can get this working with hard coded value,

sed "s/WPS_HOME.*/WPS_HOME=\/opt\/WebSphere/g" $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh > $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh_Temp
mv $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh_Temp $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh

However if the user input value is stored into a variable called WPS_HOME and then use this variable to replace....

sed "s/WPS_HOME.*/WPS_HOME='"$WPS_HOME"'/g" $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh > $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh_Temp
mv $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh_Temp $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh

This does not work. It will throw error

sed: 0602-404 Function s/WPS_HOME.*//opt/websphere/ cannot be parsed.

Can anyone suggest solving this problem? I cannot use perl here, any solution using sed or awk is fine.

Thanks,
Rijesh.

2 
a=add
b=mul
echo "addsub" | sed "s/$a/$b/"
3

Thanks for the reply.

Yes, it will work, but what will be in case if the variable is taking from user which is a valid UNIX path that contains / and need to put that variable by replacing the corresponding value to other file or value? Any idea?

4

From sed man page :

You can do something like that:

sed "s�WPS_HOME.*�WPS_HOME='$WPS_HOME'�g" $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh > $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh_Temp
mv $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh_Temp $SPLFRAMEWORK_HOME/environment/splsetupCmdLine.sh

Jean-Pierre.

5

This works fine, thank you very much. Could you please tell me what is "�" character and what is the significance of it?

Thanks,
Rijesh.

6 
echo "addsub" | sed "s/$a/$b/"

Delimiter separating ( / ) search pattern and replace pattern need not be ' / ' always, if there is ' / ' character in the input, you could change the delimiter

something like

echo "addsub" | sed "s_$a_$b_"
7

Exactly.

The use of "/" to delimit regular expressions is not a rule, just a convention. You could use any other character as long as you are consistent to yourself: "s/x/y/g" is the same as "s:x:y:g", but "s/x:y:g" won't work because once you have used a delimiting character in a regexp you have to stick with it.

Anyways, it is a good idea to escape certain characters anyways, regardless of having a workaround with other delimiting chars or not. Therefor it is advisable to have a separate sed-script modify the input before feeding it to further sed-scripts:

"s/[/\.]/\\&/g"

will "escape" any of the characters "\", "/" and "." by putting a backslash ("\") in front of them. Notice, though, that some backslashes are interpreted by the shell. Play around a bit by trying ("<spc>" is ablank character):

print - "\<spc>" | sed 's/[/\.]/\\&/g'

and modify the string enclosed in the double quotes in the "print -"-statement. Notice, how it changes the behaviour if you remove the space and find out why.

bakunin