In a bash script I have a function, in which I want to check if the passed argument contains only lowercase letters, numbers and "_":
Also to check not to be only numbers and start only with a letter
The code:
function check_name () {
if [[ $1 != [a-z0-9\\_]; then
echo The name can contain only lowercase letters, numbers and _
return 1
fi
}
The code fails, because always the condition is true and returns 1
You can do like this:
[STEP 115] $ var=abc123_
[STEP 116] $ [[ -z ${var//[_[:digit:][:lower:]]} ]] && echo yes || echo no
yes
[STEP 117] $ var=ABC
[STEP 118] $ [[ -z ${var//[_[:digit:][:lower:]]} ]] && echo yes || echo no
no
[STEP 119] $
Or
[STEP 125] $ var=abc123_
[STEP 126] $ [[ $var == +([_[:digit:][:lower:]]) ]] && echo yes || echo no
yes
[STEP 127] $ var=ABC
[STEP 128] $ [[ $var == +([_[:digit:][:lower:]]) ]] && echo yes || echo no
no
[STEP 129] $
Or
[STEP 130] $ var=abc123_
[STEP 131] $ [[ $var =~ ^[_[:digit:][:lower:]]+$ ]] && echo yes || echo no
yes
[STEP 132] $ var=ABC
[STEP 133] $ [[ $var =~ ^[_[:digit:][:lower:]]+$ ]] && echo yes || echo no
no
[STEP 134] $
extglob enabled 3) Fails for var=FOOabc123_. Add ^ and $ to your regex.