Home / Questions / 4198
Accepted
julian salas
Asked: 2020-02-15 13:21:35 +0800 CST 2020-02-15 13:21:35 +0800 CST

Regular Expressions in Bash

  • 772

I am trying to make a bash script that validates a directory using regular expressions, what I have is the following.

echo "Ingresa La ruta de tu directorio"
read ruta
if [ $ruta != '^/[a-zA-Z]$' ];then
    echo "No has ingresado una ruta valida, recuerda que la ruta inicia con /"
    echo " "
    continue
else
    if [ -d $ruta ]; then
        echo""
        echo "hey, ya tienes creado tu directorio, tal vez necesites usar otra opcion"
        continue
    fi
fi

When I enter documents, the validation works, but when entering, for example /Documents, that it is an existing directory, the operation is the same and it does not validate the expression, it is as if it will not enter the /.

How could I correctly validate the expression?

linux

3 Answers

  1. Best Answer

    To test a regular expression in bash, you must use the y operator =~and must be enclosed in double brackets [[ ]] ,

    Also, to make the script more compatible between versions , you should place the regular expression in single quotes in a variable beforehand. (Thanks @TomFenech)

    As for your regular expression you must add an +or *after [a-zA-Z]since if you don't, it captures a single character and you want to capture all of them. (use *if the value /alone is valid)

    The IF would look like this:

    regla='^/[a-zA-Z]+$'
if [[ ! $ruta =~ $regla ]]

    This is a simplified example:

    #!/bin/bash

echo "Ingresa La ruta de tu directorio"
read ruta

regla='^/[a-zA-Z]+$'
if [[ ! $ruta =~ $regla ]]; then
 echo "Tiene la barra"
else
 echo "Falta la barra"
fi
    • 5

  2. it is not necessary to declare it, it can be direct:

    if [[ "tu_cadena" =~ "regex" ]]; then

    Example:

    if [[ "hola" =~ "^[Hh]" ]]; then
    printf "Empieza con h\n"
end

    You can see more about regex at regex101.com

    • 1

  3. I think you have it backwards. First check if the user has entered the / and if not send the else if. I leave you the modified code. I've tried it and it works for me.

        read -p "Ingresa La ruta de tu directorio " ruta

if [ -d $ruta ]
then
     echo " "
     echo "hey, ya tienes creado tu directorio, tal vez necesites usar otra opcion"
     continue
elif [ $ruta != '^/[a-zA-Z]$' ]
then
   echo""
echo "No has ingresado una ruta valida, recuerda que la ruta inicia con /"
                continue
fi
    • 0