Egrep Help - UNIX for Dummies Questions & Answers

FuzzyNips · #1 (**permalink**) 11-10-2004

I'm writing a small script thats purpose is to validate a single command line argument to make sure it is an integer. Also acceptable are a leading "+" or "-", but no more than one.

Example: "5" "-2" "+4" are all valid

If its invalid I simply print out a message saying so, otherwise I just return the value (I need to remove the leading "+" though).

Here's the code I have so far:

Code:

# Checks for valid number of arguments
# Exits program with return code of 1
if [ $# -ne 1 ]; then
        echo "Invalid number of arguments; supports only one argument"

        exit 1
fi

# Checks for valid argument
echo $1 | egrep -s "^[+|-]?[0-9]+$"

# If argument is valid then return its value
# Exits program with return code of 0
if [ $? -eq 0 ]; then
        # Removes a leading '+' sign if there is one
        tr -d '+' $1
        echo $1

        exit 0
# If argument is invalid then return an error message
# Exits program with return code of 2
else
        echo "Invalid operand: $1"

        exit 2
fi

My problem is that when a valid argument is entered the cursor just moves to the next line and sits there. I'm guessing something must be wrong with my eGrep statement. I'm looking for a + or - 0 or 1 time...followed by one or more numbers...what am I doing wrong?

EDIT: It may be with my translate command sine I've never used it before. I need to delete all +'s in the (valid) argument....how do I do that?

bhargav · #2 (**permalink**) 11-10-2004

I tried some thing like this , which might help you ;

$ echo "-1" | egrep "^[\+\-]" | tr "-" " "
1
$
$ echo "+1" | egrep "^[\+\-]" | tr "+" " "
1

FuzzyNips · #3 (**permalink**) 11-10-2004

Ok I got it working finally!

Code:

# Checks for valid argument
echo $1 | egrep -s "(^[\+]?[0-9]+$)|(^[-]?[0-9]+$)"

# If argument is valid then return its value
# Exits program with return code of 0
if [ $? -eq 0 ]; then
        # Removes a leading '+' sign if there is one
        echo $1 | tr -d "+" " "

        exit 0

# If argument is invalid then return an error message
# Exits program with return code of 1
else
        echo "Invalid operand: $1"

        exit 1
fi

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