How do I replace special characters in a string within a bash script?

rhaup0317 · 06-03-2008, 09:13 AM

I have this bash script that is basically a search/replace in a text file.

I am running into issues when a user sends in a string that has special characters (quotes, spaces, =s, etc). So I think that I want to put a \ in front of each special character. Can I do it in one command or does each character needs its own command?

Or I am going about this in the wrong way?

Heres the code.

Code:

#!/bin/bash
echo "Hello!"
echo "Enter a string to be replaced:"
read old
echo "Enter a string that will replace the above string:"
read new
echo "Enter the name of a file where you want this to take place:"
read filename
#Checks to see if the file exists in the current directory
if [ -e $filename ]
then
        #saves a backup of the original file
        oldfile=$filename"_old_"`date '+%m%d%Y'`
        cat $filename > $oldfile
        #makes sure the quotes are read in correctly
        old=${old//"\""/"\\\""}
        new=${new//"\""/"\\\""}
        #performs the replacement
        sed -i 's/'$old'/'$new'/g' $filename 
        echo "Success! Your file has been updated"
else
        echo "The filename that you typed in does not exist."
fi

Uxinn · 06-03-2008, 10:18 AM

Try this
here I'm using sed "s# instead of 's/
only problematic characters now are "\" and "#" and possibly "^" at begining of line.

Code:

#!/bin/bash


echo "Hello!"
echo "Enter a string to be replaced:"
read old
echo "Enter a string that will replace the above string:"
read new
echo "Enter the name of a file where you want this to take place:"
read filename

if [ -e $filename ]
then
        #saves a backup of the original file
        oldfile=$filename"_old_"`date '+%m%d%Y'`
        cat $filename > $oldfile
        #makes sure the quotes are read in correctly
#        old=${old//"\""/"\\\""}
#        new=${new//"\""/"\\\""}
        #performs the replacement
        sed -i "s#${old}#${new}#g" $filename 
        echo "Success! Your file has been updated"
else
        echo "The filename that you typed in does not exist."
fi

rhaup0317 · 06-03-2008, 11:56 AM

Who rock da party? Uxinn!!!!!!!

Thanks dude! It works.

-Ryan