Shell Programming and Scripting

Hi All,

I'm writing a script to read a file line by line and then perform awk function on it. I am getting an error . My file has one name in it "James". I'm expecting my o/p to be youareJamesbond
James
./users.sh: line 7: =: command not found

Code:

#script to read file line by line
#adding quotes at start and end of users
#!/usr/bin/bash

while read line
    do echo $line
       $username=$(awk '{print "youare" $line "bond"}')
       echo $username
done</home/gunner/users.txt
echo $username

You don't use $ when assigning a variable.

Code:

username=$(awk '{print "youare" $line "bond"}')

You don't need awk for this, however! Never use external utilities for things you can do with builtins, especially when processing individual lines. Running awk 9,000 times for 9,000 lines is like making 9,000 phonecalls to say 9,000 words.

You don't need another variable for this, either. I'm guessing awk got resorted to because "youare$linebond" tries to use the variable $linebond and not $line. You can surround the variable with {} brackets to prevent this.

Code:

while read line
do
        echo $line
        echo "youare${line}bond"
done</home/gunner/users.txt

Lose the $ on $username in this context.

Code:

username=$(awk '{print "youare" $line "bond"}')

And as Conona688 noticed $line will never get expanded becuase it is between two single quote characters and the "awk" was not needed.

Code:

username="youare${line}bond"

Thank you all, that worked. I was able to get awk working also well spotted methyl. I'm still new to scripting in shell so not really aware of perfomance tuning. Thanks for the tip though.

Cheers

It's not "tuning", the difference between shell internals and external utilities is very important. Imagine if you were loading and quitting your web browser every time you wanted to browse to a different web page. That's what running awk for one line is like. It can process 10,000 lines far faster than a shell could, but takes time to load and quit.

You need to learn what builtin operations your shell has to write decent code. The advanced bash scripting guide can be very useful even if you weren't using bash, but is especially useful since you are. Check out the 'reference cards' section especially.

Thanks for the link mate. I'll check this out . As always appreciate your time on this one.

Cheers