Using the not equal operator for string comparison
I guess you're looking for:
if [ "$PHONE_TYPE" != "NORTEL" ] && [ "$PHONE_TYPE" != "NEC" ] &&
[ "$PHONE_TYPE" != "CISCO" ]
The rules for these equivalents are called De Morgan's laws and in your case meant:
not(A || B || C) => not(A) && not(B) && not (C)
Note the change in the boolean operator or and and.
Whereas you tried to do:
not(A || B || C) => not(A) || not(B) || not(C)
Which obviously doesn't work.
A much shorter way would be:
if [[ ! $PHONE_TYPE =~ ^(NORTEL|NEC|CISCO)$ ]]; then
echo "Phone type must be nortel, cisco or nec."
fi
^
– To match a starting at the beginning of line$
– To match end of the line=~
- Bash's built-in regular expression comparison operator
Good answers, and an invaluable lesson ;) Only want to supplement with a note.
What type of test one choose to use is highly dependent on code, structure, surroundings etc.
An alternative could be to use a switch or case
statement as in:
case "$PHONE_TYPE" in
"NORTEL"|"NEC"|"CISCO")
echo "OK"
;;
*)
echo "Phone type must be nortel,cisco or nec"
;;
esac
As a second note you should be careful by using upper-case variable names. This is to prevent collision between variables introduced by the system, which almost always is all upper case. Thus $phone_type
instead of $PHONE_TYPE
.
Though that one is safe, if you have as habit using all upper case, one day you might say IFS="boo"
and you're in a world of hurt.
It will also make it easier to spot which is what.
Not a have to but a would strongly consider.
It is also presumably a good candidate for a function. This mostly makes the code easier to read and maintain. E.g.:
valid_phone_type()
{
case "$1" in
"NORTEL"|"NEC")
return 0;;
*)
echo "Model $1 is not supported"
return 1;;
esac
}
if ! valid_phone_type "$phone_type"; then
echo "Bye."
exit 1
fi