Shell Programming and Scripting

Hi,

I'm trying to assign the output of a command to a variable and then concat it with another string, however, it keeps overwriting the original string instead of adding on to the end of the string.

Contents of test.txt --> This is a test

var1="`head -n 1 test.txt`"
echo $var1 (This is a test)

var1=$var1"123"
echo $var1 (123s is a test [instead of: This is a test123)

The issue has something to do with the first line. If I simply assign a string like this:
var1="This is a test" , then it all works, but when I try to assign the output of a command to a variable, it does not add to the string properly.

Does anyone know how to get around this??

Thanks!!

Try it like this:

Code:

/tmp$ cat test.txt
This is a test
This is also a test
/tmp$ var1="`head -n 1 test.txt`"
/tmp$ echo $var1
This is a test
/tmp$ var1=${var1}123
/tmp$ echo $var1
This is a test123
/tmp$

Modern Bourne shell variants support $(command) notation as well, which allows nesting and, in my opinion, is easier on the eyes.

Some, such as bash, allow you to do fun stuff such as this=$(<file.txt) to grab the contents of file.txt in the variable "this".

I agree there, but I used the back-quotes as that's what the OP used while asking the question. You *can* nest commands using backquotes as well, but the number of escape chars would increase with every level.

Thanks for both of your replies.

blowtorch - I tried the code you have given, but ended up with the same result --> 123s is a test

I am using Korn Shell which comes with the Microsoft Services for Unix Applications (SUA) add on component to Windows Server 2003 R2.

Is there a command which I can use to insert a string into the other string - either in the middle or at the end? For example, it would count the number of characters in "This is a test" and then append after then 14th character.

Found the issue!

As always, with these types of problems, it was some minor annoyance that was causing it - a carriage return/line feed in the test.txt file after the string.

If I do a wc -c on the file it would give me 16 instead of 14 (2 extra for the CRLF).

Thanks for your help!

I've changed my code to use the var1=${var1}123 (thanks blowtorch) notation and also the var1=$(<test.txt) (thanks macosta) notation, which looks cleaner.