linuxbashcommand-linenewlinecat

Bash: redirect `cat` to file without newline


I have two files that I am concatenating into a single file, but I am also adding user input between the two files. The problem is that a newline is being inserted after the first file, the rest of it works as desired.

touch newFile
cat file1 > newFile
echo -n $userInput >> newFile
cat file2 >> newFile

How do I prevent or remove the newline when file1 is added to newFile? If I cat file1 there seems to be a newline added by cat but everything I see about cat says it doesn't do that. If I vim file1 there's not a blank line at the end of the file that would indicate the newline is a part of the file, so either cat is actually adding a newline, or the redirect > is doing it, or echo adds a newline at the beginning of its output, none of which would be desirable in this situation. One solution I saw was to use

cat file1 | tr -d '\n'

but that discards all the newlines in the file, also not desirable. So, to repeat my question:

How do I cat file1 into the new file and add user input without adding the newline between them?

(cat is not a requirement, but I am not familiar with printf, so if that's the solution then please elaborate on its use).


Solution

  • With these inputs:

    userInput="Test Test Test"
    
    echo "Line 1
    Line 2
    Line 3" >file1
    
    echo "Line 4
    Line 5
    Line 6" >file2
    

    I would do:

    printf "%s%s%s" "$(cat file1)" "$userInput" "$(cat file2)" >newfile
    

    The creation of >newfile is equivalent to touch and adding content in your first step. A bit easier to see intent with this.

    I get:

    $ cat newfile
    Line 1
    Line 2
    Line 3Test Test TestLine 4
    Line 5
    Line 6