Comparing strings with special characters using if-loop does not work

Question

I want to compare each line of a particular file with the following string

#orb_plugins = ["local_log_stream", "iiop_profile", "giop", "iiop"];

("file.txt" contains this particular line)

I tried the following by prefixing special characters with '\'

IFS=''
while read -r line
do
  if [ "$line" == "#orb_plugins = \[\"local_log_stream\", \"iiop_profile\", \"giop\", \"iiop\"\];" ]
  then
    echo "String found. Do remaining steps"
  fi
done < file.txt

Solution 1

Most simple method is to use single quotes on the right hand side:

if [ "$line" == '#orb_plugins = ["local_log_stream", "iiop_profile", "giop", "iiop"];' ]

This way the string to be matched is interpreted literally.

If you prefer using double quotes, you must not escape the brackets ([]), but only the double quotes (""):

if [ "$line" == "#orb_plugins = [\"local_log_stream\", \"iiop_profile\", \"giop\", \"iiop\"];" ]

Solution 2

Why not using the right tool for this job, i.e. grep:

grep -qxFf- file.txt <<\IN && printf %s\\n "String found. Do remaining steps"
#orb_plugins = ["local_log_stream", "iiop_profile", "giop", "iiop"];
IN

This stops reading the file as soon as a match is found. It's also (on average) about 100 times faster than your while read loop.

Comments

[Rui F Ribeiro]

You are trying to define an array there, but then you do not use it, I think. Would not be easier to use a case statement?

[Anusuya Nandi]

Thanks for the tip. This is just part of my 100 line code. I am not skilled enough to use grep/sed instead of using grep in all places. As you mentioned, the script runs too slow.

[Anusuya Nandi]

Using single quotes solves the problem. Thank you