How do I subtract characters in bash?

[tux101]

I need help making a calculating script for bash. Would someone please help me out?

What I am trying to do is enter an entry, the script will do a modifcation of the entry. Then use the sum to carry out another task.

Lets say I ran the script, and the script asked me for the entry with

echo -n "entry: "
read entry


And I put in there "tux101@fakemail.com"

The script then carries out a simple calculation of subtracting the "101@fakemail.com" And then converts the "tux" into $I.

Then the script can use the $I to carry out other commands. Lets say it uses $I for a confirmation that will echo "Hi, Tux! Is tux101@fakemail.com spelled correctly?"

Don't worry about the confirmation part. I just want to know how I can get the script to modify an entry and then use the sum of it as a $I.

[cwaldbieser]

I need help making a calculating script for bash. Would someone please help me out?

What I am trying to do is enter an entry, the script will do a modifcation of the entry. Then use the sum to carry out another task.

Lets say I ran the script, and the script asked me for the entry with

echo -n "entry: "
read entry


And I put in there "tux101@fakemail.com"

The script then carries out a simple calculation of subtracting the "101@fakemail.com" And then converts the "tux" into $I.

Then the script can use the $I to carry out other commands. Lets say it uses $I for a confirmation that will echo "Hi, Tux! Is tux101@fakemail.com spelled correctly?"

Don't worry about the confirmation part. I just want to know how I can get the script to modify an entry and then use the sum of it as a $I.

The following bash syntax may help:

${var:N}
${var#pattern}
${var##pattern}
${var%pattern}
${var%%pattern}
${var/pattern/string}

They are all ways to manipulate string variables. You could use tools like sed or awk, too.

For your example:


$ x="tux101@fakemail.com"
$ echo ${x%@*}
tux101