Shell = Check if variable begins with #
Solution 1:
Your original approach would work just fine if you escaped the hash:
$ [[ '#snort' == \#* ]]; echo $?
0
Another approach would be slicing off the first character of the variable's content, using "Substring Expansion":
if [[ ${x:0:1} == '#' ]]
then
echo 'yep'
else
echo 'nope'
fi
yep
From the Bash man page:
${parameter:offset}
${parameter:offset:length}
Substring Expansion. Expands to up to length characters of
parameter starting at the character specified by offset. If
length is omitted, expands to the substring of parameter start-
ing at the character specified by offset. length and offset are
arithmetic expressions (see ARITHMETIC EVALUATION below).
length must evaluate to a number greater than or equal to zero.
If offset evaluates to a number less than zero, the value is
used as an offset from the end of the value of parameter. If
parameter is @, the result is length positional parameters
beginning at offset. If parameter is an array name indexed by @
or *, the result is the length members of the array beginning
with ${parameter[offset]}. A negative offset is taken relative
to one greater than the maximum index of the specified array.
Note that a negative offset must be separated from the colon by
at least one space to avoid being confused with the :- expan-
sion. Substring indexing is zero-based unless the positional
parameters are used, in which case the indexing starts at 1.
Solution 2:
POSIX-compatible version:
[ "${var%${var#?}}"x = '#x' ] && echo yes
or:
[ "${var#\#}"x != "${var}x" ] && echo yes
or:
case "$var" in
\#*) echo yes ;;
*) echo no ;;
esac
Solution 3:
I know this may be heresy, but for this kind of things I'd rather use grep or egrep rather than doing it from within the shell. It's a little more costly (I guess) but for me this solution's readability offsets that. It's a matter of personal taste though, of course.
So:
myvar=" #comment asfasfasdf"
if ! echo $myvar | egrep -q '^ *#'
then
echo "not a comment"
else
echo "commented out"
fi
It works with or without leading spaces. If you'd like to account for leading tabs also, use egrep -q '^[ \t]*#' instead.