Weird behaviour of string variables in bash script...Please help!

Question

Hi all,

I'm going nuts with this...let me explain...

I have a very simple Bash script with a function in it that receives 3 arguments. Those arguments are all strings. Everything was working fine 'til I had to pass a string with whitespaces to the function.

I also have some test code to call the function (whose name is substracFromFile):

# try the function

PATTERN=`echo -e '<Location test14>'`

echo "PATTERN IS $PATTERN"

HEADERPATTERN=`echo -e '<Location [a-zA-Z0-9]*>'`

echo "HEADERPATTERN IS $HEADERPATTERN"

FILE="subversion.conf"

echo "FILE IS $FICHERO"

substracFromFile $PATTERN $HEADERPATTERN $FILE

The output of this is:

PATTERN IS <Location prueba14>
HEADERPATTERN IS <Location [a-zA-Z0-9]*>
FILE IS subversion.conf
PATTERN ARGUMENT IS <Location
HEADERPATTERN ARGUMENT IS prueba14>
FILE ARGUMENT IS <Location
grep: <Location: No such file or directory
expr: syntax error

As you can see, when arguments are passed to the function and I echoed them to screen they are somehow splitted in the white space...let me show you the function initial code:

function substracFromFile
{

        PATTERN=$1

        HEADERPATTERN=$2

        FILE=$3

        # Debug only
        echo "HEADER ARGUMENT IS $PATTERN"

        # Debug only
        echo "HEADERPATTERN ARGUMENT IS $HEADERPATTERN"

        # Debug only
        echo "FILE ARGUMENT IS $FILE"

This was working sweet as long as passed strings had no whitespaces at all. When I call the function strings seem to be ok, but I don't understand why they are splitted once the function is called....I'm sure this is something pretty dull, but I just don't get it...

Thanks in advance, Alex

Answer 1

Parts of your question are inconsistent with other parts. For example:

FILE="subversion.conf"

echo "FILE IS $FICHERO"

But I'm assuming those are just errors made while posting the question.

As ghostdog74 mentioned in a comment, you need to quote variables that contain whitespace. In particular, this line should have quotes around the variables:

substracFromFile "$PATTERN" "$HEADERPATTERN" "$FILE"

Also, I don't see why you're using echo to set variables in lines such as this one:

PATTERN=`echo -e '<Location test14>'`

This could simply be:

PATTERN='<Location test14>'

If the value sometimes has escaped special characters in it, you can use one of these methods:

PATTERN=$'value\nwith\tescapes'

which would have "value" newline "with" tab "escapes" as its value.

Also, I recommend getting in the habit of not using all-caps for variable names. This will reduce the chance of name collisions with Bash's built-in variables.

Answer 2

Thanks for the info!

Best regards