I am trying to compare strings in bash. I already found an answer on how to do it on stackoverflow. In script I am trying, I am using the code submitted by Adam in the mentioned question:
#!/bin/bash
string='My string';
if [[ "$string" == *My* ]]
then
echo "It's there!";
fi
needle='y s'
if [[ "$string" == *"$needle"* ]]; then
echo "haystack '$string' contains needle '$needle'"
fi
I also tried approach from ubuntuforums that you can find in 2nd post
if [[ $var =~ regexp ]]; then
#do something
fi
In both cases I receive error:
[[: not found
What am I doing wrong?
[[ is a bash-builtin. Your /bin/bash doesn't seem to be an actual bash.
How you are running your script? If you did with
$ sh myscript
you should try:
$ bash myscript
or, if the script is executable:
$ ./myscript
sh and bash are two different shells. While in the first case you are passing your script as an argument to the sh interpreter, in the second case you decide on the very first line which interpreter will be used.
Is the first line in your script:
#!/bin/bash
or
#!/bin/sh
the sh shell produces this error messages, not bash
I had this problem when installing Heroku Toolbelt
This is how I solved the problem
$ ls -l /bin/sh
lrwxrwxrwx 1 root root 4 ago 15 2012 /bin/sh -> dash
As you can see, /bin/sh is a link to "dash" (not bash), and [[ is bash syntactic sugarness. So I just replaced the link to /bin/bash. Careful using rm like this in your system!
$ sudo rm /bin/sh
$ sudo ln -s /bin/bash /bin/sh
As @Ansgar mentioned, [[ is a bashism, ie built into Bash and not available for other shells. If you want your script to be portable, use [. Comparisons will also need a different syntax: change == to =.
Specify bash instead of sh when running the script. I personally noticed they are different under ubuntu 12.10:
bash script.sh arg0 ... argn
来源：https://stackoverflow.com/questions/12230690/string-comparison-in-bash-not-found